Resources

  • ResourceLoaderAware

  • Built-in Resource Implementations

  • ClassPathXmlApplicationContext

  • Wildcards

  • FileSystemResource Caveats

  • InputStreamSource

  • WritableResource :description: 本文讨论了 Spring 的 Resource 抽象，它允许以统一的方式访问不同类型的资源。Resource 接口表示可用于加载、读取和写入资源的对象。Spring 提供了多种内置的 Resource 实现（例如 UrlResource、ClassPathResource 和 FileSystemResource），每种实现都针对特定类型的资源进行了优化。应用程序上下文充当 ResourceLoader，它允许以应用程序上下文类型特定的方式加载资源。ResourcePatternResolver 接口扩展了 ResourceLoader，允许使用模式（例如 Ant 路径模式）解析资源位置。开发人员还可以实现 ResourceLoaderAware 接口以直接加载资源或使用基于注释的自动装配来注入 Resource 对象。

本章介绍了 Spring 如何处理资源以及如何在 Spring 中使用资源。它包括以下主题：

This chapter covers how Spring handles resources and how you can work with resources in Spring. It includes the following topics:

Introduction

不幸的是，Java 的标准 java.net.URL 类和各种 URL 前缀的标准处理程序不足以完全用于访问低级资源。例如，没有用于访问需要从类路径或相对于 ServletContext 获取的资源的标准化 URL 实现方式。虽然可以注册专门的 URL 前缀的新处理程序（类似于 http: 等前缀的现有处理程序），但这通常非常复杂，并且 URL 接口仍然缺少一些理想的功能，例如检查所指向的资源是否存在的方法。

Java’s standard java.net.URL class and standard handlers for various URL prefixes, unfortunately, are not quite adequate enough for all access to low-level resources. For example, there is no standardized URL implementation that may be used to access a resource that needs to be obtained from the classpath or relative to a ServletContext. While it is possible to register new handlers for specialized URL prefixes (similar to existing handlers for prefixes such as http:), this is generally quite complicated, and the URL interface still lacks some desirable functionality, such as a method to check for the existence of the resource being pointed to.

The Resource Interface

Spring 的 Resource 接口位于 org.springframework.core.io. 包中，旨在成为一个更强大的接口来抽象对低级资源的访问。以下列表提供了 Resource 接口的概述。请参阅 Resource javadoc 以了解进一步详情。

Spring’s Resource interface located in the org.springframework.core.io. package is meant to be a more capable interface for abstracting access to low-level resources. The following listing provides an overview of the Resource interface. See the Resource javadoc for further details.

public interface Resource extends InputStreamSource {

	boolean exists();

	boolean isReadable();

	boolean isOpen();

	boolean isFile();

	URL getURL() throws IOException;

	URI getURI() throws IOException;

	File getFile() throws IOException;

	ReadableByteChannel readableChannel() throws IOException;

	long contentLength() throws IOException;

	long lastModified() throws IOException;

	Resource createRelative(String relativePath) throws IOException;

	String getFilename();

	String getDescription();
}

正如 Resource 接口的定义所示，它扩展了 InputStreamSource 接口。以下列表显示了 InputStreamSource 接口的定义：

As the definition of the Resource interface shows, it extends the InputStreamSource interface. The following listing shows the definition of the InputStreamSource interface:

public interface InputStreamSource {

	InputStream getInputStream() throws IOException;
}

Resource 接口中一些最重要的方法是：

Some of the most important methods from the Resource interface are:

  • getInputStream(): Locates and opens the resource, returning an InputStream for reading from the resource. It is expected that each invocation returns a fresh InputStream. It is the responsibility of the caller to close the stream.

  • exists(): Returns a boolean indicating whether this resource actually exists in physical form.

  • isOpen(): Returns a boolean indicating whether this resource represents a handle with an open stream. If true, the InputStream cannot be read multiple times and must be read once only and then closed to avoid resource leaks. Returns false for all usual resource implementations, with the exception of InputStreamResource.

  • getDescription(): Returns a description for this resource, to be used for error output when working with the resource. This is often the fully qualified file name or the actual URL of the resource.

其他方法允许你获取表示资源的实际 URL 或 File 对象（如果底层实现兼容并支持该功能）。

Other methods let you obtain an actual URL or File object representing the resource (if the underlying implementation is compatible and supports that functionality).

Resource 接口的一些实现也实现了扩展的 WritableResource 接口以获取支持对其写入的资源。

Some implementations of the Resource interface also implement the extended WritableResource interface for a resource that supports writing to it.

Spring 本身在需要资源时广泛使用 Resource 抽象，作为许多方法签名中的参数类型。某些 Spring API 中的其他方法（例如，到各种 ApplicationContext 实现的构造函数）使用一个 String，它以未修饰或简单形式用于创建适合该上下文实现的 Resource，或通过 String 路径上的专用前缀，允许调用者指定必须创建和使用的特定 Resource 实现。

Spring itself uses the Resource abstraction extensively, as an argument type in many method signatures when a resource is needed. Other methods in some Spring APIs (such as the constructors to various ApplicationContext implementations) take a String which in unadorned or simple form is used to create a Resource appropriate to that context implementation or, via special prefixes on the String path, let the caller specify that a specific Resource implementation must be created and used.

虽然 Resource 接口在很多情况下与 Spring 及其本身一起使用，但它实际上非常方便，在你自己的代码中将其作为一般的实用程序类，用于访问资源，即使你的代码不知道或不关心 Spring 的任何其他部分。虽然这会将你的代码与 Spring 耦合，但实际上只将其与一小部分实用程序类耦合，这些类用作 URL 的更强大的替换，并且可以被视为你为此目的将要使用的任何其他库的等效项。

While the Resource interface is used a lot with Spring and by Spring, it is actually very convenient to use as a general utility class by itself in your own code, for access to resources, even when your code does not know or care about any other parts of Spring. While this couples your code to Spring, it really only couples it to this small set of utility classes, which serves as a more capable replacement for URL and can be considered equivalent to any other library you would use for this purpose.

Resource 抽象不取代功能。它在可能的情况下对功能进行包装。例如，UrlResource 封装一个 URL 并使用被封装的 URL 来完成它的工作。

The Resource abstraction does not replace functionality. It wraps it where possible. For example, a UrlResource wraps a URL and uses the wrapped URL to do its work.

Built-in Resource Implementations

Spring 包括几个内置的 Resource 实现：

Spring includes several built-in Resource implementations:

对于在 Spring 中可用的 Resource 实现的完整列表，请参阅 Resource javadoc 的“所有已知实现类”部分。

For a complete list of Resource implementations available in Spring, consult the "All Known Implementing Classes" section of the Resource javadoc.

UrlResource

UrlResource 封装一个 java.net.URL，可以用于访问任何通常可以使用 URL 访问的对象，例如文件、HTTPS 目标、FTP 目标等。所有 URL 都有标准的 String 表示形式，以便使用适当的标准化前缀来指示一种 URL 类型与另一种 URL 类型。这包括 file:（用于访问文件系统路径）、https:（用于通过 HTTPS 协议访问资源）、ftp:（用于通过 FTP 访问资源）等。

UrlResource wraps a java.net.URL and can be used to access any object that is normally accessible with a URL, such as files, an HTTPS target, an FTP target, and others. All URLs have a standardized String representation, such that appropriate standardized prefixes are used to indicate one URL type from another. This includes file: for accessing filesystem paths, https: for accessing resources through the HTTPS protocol, ftp: for accessing resources through FTP, and others.

UrlResource 是通过明确使用 UrlResource 构造函数由 Java 代码创建的，但在你调用获取一个表示路径的 String 参数的 API 方法时通常会隐式创建 UrlResource。对于后一种情况，一个 JavaBeans PropertyEditor 最终决定创建哪种类型的 Resource。如果路径字符串包含属性编辑器（即）公认的前缀（例如 classpath:），它会为该前缀创建一个适合的专门 Resource。但是，如果它不识别该前缀，它会假定该字符串是一个标准 URL 字符串，并创建一个 UrlResource。

A UrlResource is created by Java code by explicitly using the UrlResource constructor but is often created implicitly when you call an API method that takes a String argument meant to represent a path. For the latter case, a JavaBeans PropertyEditor ultimately decides which type of Resource to create. If the path string contains a well-known (to property editor, that is) prefix (such as classpath:), it creates an appropriate specialized Resource for that prefix. However, if it does not recognize the prefix, it assumes the string is a standard URL string and creates a UrlResource.

ClassPathResource

此类表示应从类路径获取的资源。它使用线程上下文类加载器、给定的类加载器或给定的类加载资源。

This class represents a resource that should be obtained from the classpath. It uses either the thread context class loader, a given class loader, or a given class for loading resources.

此 Resource 实现支持将类路径资源解析为 java.io.File，如果类路径资源驻留在文件系统中，但对于驻留在 JAR 中且尚未展开（通过 servlet 引擎或无论环境是什么）到文件系统的类路径资源不支持。为了解决这个问题，各种 Resource 实现始终支持作为 java.net.URL 进行解析。

This Resource implementation supports resolution as a java.io.File if the class path resource resides in the file system but not for classpath resources that reside in a jar and have not been expanded (by the servlet engine or whatever the environment is) to the filesystem. To address this, the various Resource implementations always support resolution as a java.net.URL.

ClassPathResource 是通过明确使用 ClassPathResource 构造函数由 Java 代码创建的，但在你调用获取一个表示路径的 String 参数的 API 方法时通常会隐式创建 ClassPathResource。对于后一种情况，一个 JavaBeans PropertyEditor 识别字符串路径上的特殊前缀 classpath:，并在该情况下创建一个 ClassPathResource。

A ClassPathResource is created by Java code by explicitly using the ClassPathResource constructor but is often created implicitly when you call an API method that takes a String argument meant to represent a path. For the latter case, a JavaBeans PropertyEditor recognizes the special prefix, classpath:, on the string path and creates a ClassPathResource in that case.

FileSystemResource

这是一个适用于 java.io.File 控制的 Resource 实现。它还支持 java.nio.file.Path 控制，使用 Spring 的标准基于字符串的路径转换，但通过 java.nio.file.Files API 执行所有操作。相反，对于基于 java.nio.path.Path 的纯支持，使用 PathResource。FileSystemResource 支持作为 File 和 URL 进行解析。

This is a Resource implementation for java.io.File handles. It also supports java.nio.file.Path handles, applying Spring’s standard String-based path transformations but performing all operations via the java.nio.file.Files API. For pure java.nio.path.Path based support use a PathResource instead. FileSystemResource supports resolution as a File and as a URL.

PathResource

这是一个适用于 java.nio.file.Path 控制的 Resource 实现，通过 Path API 执行所有操作和转换。它支持作为 File 和 URL 进行解析，还实现了扩展的 WritableResource 接口。PathResource 实际上是一个基于 java.nio.path.Path 的 FileSystemResource 的纯替代品，具有不同的 createRelative 行为。

This is a Resource implementation for java.nio.file.Path handles, performing all operations and transformations via the Path API. It supports resolution as a File and as a URL and also implements the extended WritableResource interface. PathResource is effectively a pure java.nio.path.Path based alternative to FileSystemResource with different createRelative behavior.

ServletContextResource

这是一个适用于 ServletContext 资源的 Resource 实现，可以解释相关 Web 应用程序根目录内的相对路径。

This is a Resource implementation for ServletContext resources that interprets relative paths within the relevant web application’s root directory.

它始终支持流访问和 URL 访问，但仅在 Web 应用程序存档已展开且该资源实际上存在于文件系统上时才允许 java.io.File 访问。它是否展开并存在于文件系统上，或者是否直接从 JAR 或数据库等其他地方（这是可以想象的）进行访问，实际上取决于 Servlet 容器。

It always supports stream access and URL access but allows java.io.File access only when the web application archive is expanded and the resource is physically on the filesystem. Whether or not it is expanded and on the filesystem or accessed directly from the JAR or somewhere else like a database (which is conceivable) is actually dependent on the Servlet container.

InputStreamResource

InputStreamResource 是给定 InputStream 的 Resource 实现。仅当没有特定的 Resource 实现适用时才应该使用它。具体而言，在可能的情况下，优先使用 ByteArrayResource 或任何基于文件的 Resource 实现。

An InputStreamResource is a Resource implementation for a given InputStream. It should be used only if no specific Resource implementation is applicable. In particular, prefer ByteArrayResource or any of the file-based Resource implementations where possible.

与其他 Resource 实现不同，这是一个已经打开的资源的描述符。因此，它从 isOpen() 返回 true。如果您需要将资源描述符保留在某个地方或需要多次读取流，请不要使用它。

In contrast to other Resource implementations, this is a descriptor for an already-opened resource. Therefore, it returns true from isOpen(). Do not use it if you need to keep the resource descriptor somewhere or if you need to read a stream multiple times.

ByteArrayResource

这是一个给定字节数组的 Resource 实现。它为给定的字节数组创建 ByteArrayInputStream。

This is a Resource implementation for a given byte array. It creates a ByteArrayInputStream for the given byte array.

这对于从任何给定的字节数组加载内容非常有用，而无需使用一次性 InputStreamResource。

It is useful for loading content from any given byte array without having to resort to a single-use InputStreamResource.

The ResourceLoader Interface

ResourceLoader 接口旨在由可以返回（即，加载）Resource 实例的对象实现。以下列表显示了 ResourceLoader 接口定义：

The ResourceLoader interface is meant to be implemented by objects that can return (that is, load) Resource instances. The following listing shows the ResourceLoader interface definition:

public interface ResourceLoader {

	Resource getResource(String location);

	ClassLoader getClassLoader();
}

所有应用程序上下文都实现了 ResourceLoader 接口。因此，可以使用所有应用程序上下文来获取 Resource 实例。

All application contexts implement the ResourceLoader interface. Therefore, all application contexts may be used to obtain Resource instances.

当您在特定应用程序上下文中调用 getResource()，并且指定的 location path 没有特定前缀时，您会得到一个适合于特定应用程序上下文的 Resource 类型。例如，假设运行了以下代码段来针对 ClassPathXmlApplicationContext 实例：

When you call getResource() on a specific application context, and the location path specified doesn’t have a specific prefix, you get back a Resource type that is appropriate to that particular application context. For example, assume the following snippet of code was run against a ClassPathXmlApplicationContext instance:

  • Java

  • Kotlin

Resource template = ctx.getResource("some/resource/path/myTemplate.txt");
val template = ctx.getResource("some/resource/path/myTemplate.txt")

对于 ClassPathXmlApplicationContext，该代码返回 ClassPathResource。如果针对 FileSystemXmlApplicationContext 实例运行相同的方法，它将返回 FileSystemResource。对于 WebApplicationContext，它将返回 ServletContextResource。它同样会为每个上下文返回适当的对象。

Against a ClassPathXmlApplicationContext, that code returns a ClassPathResource. If the same method were run against a FileSystemXmlApplicationContext instance, it would return a FileSystemResource. For a WebApplicationContext, it would return a ServletContextResource. It would similarly return appropriate objects for each context.

因此，您可以以适合特定应用程序上下文的样式加载资源。

As a result, you can load resources in a fashion appropriate to the particular application context.

另一方面，您还可以强制使用 ClassPathResource，而不管应用程序上下文类型如何，方法是指定特殊的前缀 classpath:，如下例所示：

On the other hand, you may also force ClassPathResource to be used, regardless of the application context type, by specifying the special classpath: prefix, as the following example shows:

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  • Kotlin

Resource template = ctx.getResource("classpath:some/resource/path/myTemplate.txt");
val template = ctx.getResource("classpath:some/resource/path/myTemplate.txt")

同样，您可以通过指定任何标准的 java.net.URL 前缀来强制使用 UrlResource。以下示例使用前缀 file 和 https:

Similarly, you can force a UrlResource to be used by specifying any of the standard java.net.URL prefixes. The following examples use the file and https prefixes:

  • Java

  • Kotlin

Resource template = ctx.getResource("file:///some/resource/path/myTemplate.txt");
val template = ctx.getResource("file:///some/resource/path/myTemplate.txt")

  • Java

  • Kotlin

Resource template = ctx.getResource("https://myhost.com/resource/path/myTemplate.txt");
val template = ctx.getResource("https://myhost.com/resource/path/myTemplate.txt")

下表总结了将 String 对象转换为 Resource 对象的策略：

The following table summarizes the strategy for converting String objects to Resource objects:

Table 1. Resource strings
Prefix Example Explanation

classpath:

classpath:com/myapp/config.xml

Loaded from the classpath.

file:

file:///data/config.xml

Loaded as a URL from the filesystem. See also FileSystemResource Caveats.

https:

https://myserver/logo.png

Loaded as a URL.

(none)

/data/config.xml

Depends on the underlying ApplicationContext.

The ResourcePatternResolver Interface

ResourcePatternResolver 接口是对 ResourceLoader 接口的扩展，它定义了将位置模式（例如，Ant 风格路径模式）解析为 Resource 对象的策略。

The ResourcePatternResolver interface is an extension to the ResourceLoader interface which defines a strategy for resolving a location pattern (for example, an Ant-style path pattern) into Resource objects.

public interface ResourcePatternResolver extends ResourceLoader {

	String CLASSPATH_ALL_URL_PREFIX = "classpath*:";

	Resource[] getResources(String locationPattern) throws IOException;
}

正如上面所见，此接口还定义了一个针对类路径中的所有匹配资源特殊 classpath*: 资源前缀。请注意，在这种情况下，资源位置应为不含占位符的路径，例如 classpath*:/config/beans.xml。JAR 文件或类路径中的不同目录可以包含具有相同路径和名称的多文件。有关使用 classpath*: 资源前缀通配符支持的更多详细信息，请参阅 Wildcards in Application Context Constructor Resource Paths 及其子部分。

As can be seen above, this interface also defines a special classpath*: resource prefix for all matching resources from the class path. Note that the resource location is expected to be a path without placeholders in this case — for example, classpath*:/config/beans.xml. JAR files or different directories in the class path can contain multiple files with the same path and the same name. See Wildcards in Application Context Constructor Resource Paths and its subsections for further details on wildcard support with the classpath*: resource prefix.

可以检查传入 ResourceLoader（例如，通过 ResourceLoaderAware 语义提供的 ResourceLoader）是否也实现了此扩展接口。

A passed-in ResourceLoader (for example, one supplied via ResourceLoaderAware semantics) can be checked whether it implements this extended interface too.

PathMatchingResourcePatternResolver 是一个独立实现，可以在 ApplicationContext 外部使用，它也由 ResourceArrayPropertyEditor 用于填充 Resource[] bean 属性。PathMatchingResourcePatternResolver 能够将指定资源位置路径解析为一个或多个匹配的 Resource 对象。源路径可能是简单路径，它具有与目标 Resource 对应的一对一映射，或者可以包含特殊 classpath*: 前缀和/或内部 Ant 样式正则表达式（使用 Spring 的 org.springframework.util.AntPathMatcher 实用程序进行匹配）。后两者实际上都是通配符。

PathMatchingResourcePatternResolver is a standalone implementation that is usable outside an ApplicationContext and is also used by ResourceArrayPropertyEditor for populating Resource[] bean properties. PathMatchingResourcePatternResolver is able to resolve a specified resource location path into one or more matching Resource objects. The source path may be a simple path which has a one-to-one mapping to a target Resource, or alternatively may contain the special classpath*: prefix and/or internal Ant-style regular expressions (matched using Spring’s org.springframework.util.AntPathMatcher utility). Both of the latter are effectively wildcards.

任何标准 ApplicationContext 中的默认 ResourceLoader 实际上是实现了 ResourcePatternResolver 接口的 PathMatchingResourcePatternResolver 的一个实例。对于 ApplicationContext 实例本身也是如此，它还实现了 ResourcePatternResolver 接口并将委托给默认的 PathMatchingResourcePatternResolver。

The default ResourceLoader in any standard ApplicationContext is in fact an instance of PathMatchingResourcePatternResolver which implements the ResourcePatternResolver interface. The same is true for the ApplicationContext instance itself which also implements the ResourcePatternResolver interface and delegates to the default PathMatchingResourcePatternResolver.

The ResourceLoaderAware Interface

ResourceLoaderAware 接口是一个特殊的回调接口，用于标识希望提供 ResourceLoader 引用。以下列表显示了 ResourceLoaderAware 接口的定义：

The ResourceLoaderAware interface is a special callback interface which identifies components that expect to be provided a ResourceLoader reference. The following listing shows the definition of the ResourceLoaderAware interface:

public interface ResourceLoaderAware {

	void setResourceLoader(ResourceLoader resourceLoader);
}

当一个类实现 ResourceLoaderAware 并部署到应用程序上下文中（作为 Spring 管理的 bean）时，应用程序上下体会将其识别为 ResourceLoaderAware。然后，应用程序上下文调用 setResourceLoader(ResourceLoader)，将自身作为参数提供（请记住，Spring 中的所有应用程序上下文都实现了 ResourceLoader 接口）。

When a class implements ResourceLoaderAware and is deployed into an application context (as a Spring-managed bean), it is recognized as ResourceLoaderAware by the application context. The application context then invokes setResourceLoader(ResourceLoader), supplying itself as the argument (remember, all application contexts in Spring implement the ResourceLoader interface).

由于 ApplicationContext 是一个 ResourceLoader，因此 bean 也可以实现 ApplicationContextAware 接口，并使用提供的应用程序上下文直接加载资源。但是，通常情况下，如果你只需要它，最好使用专门的 ResourceLoader 接口。代码只会与资源加载接口（可以认为是实用程序接口）耦合，而不会与整个 Spring ApplicationContext 接口耦合。

Since an ApplicationContext is a ResourceLoader, the bean could also implement the ApplicationContextAware interface and use the supplied application context directly to load resources. However, in general, it is better to use the specialized ResourceLoader interface if that is all you need. The code would be coupled only to the resource loading interface (which can be considered a utility interface) and not to the whole Spring ApplicationContext interface.

在应用程序组件中，你还可以依赖 ResourceLoader 的自动装配，而不是实现 ResourceLoaderAware 接口。traditional constructor 和 byType 自动装配模式（如 Autowiring Collaborators 中所述）能够分别为构造函数参数或 setter 方法参数提供 ResourceLoader 。为了获得更大的灵活性（包括自动装配字段和多参数方法的能力），请考虑使用基于注释的自动装配功能。在这种情况下，ResourceLoader 被自动装配到字段、构造函数参数或方法参数中，该字段、参数或方法期待 ResourceLoader 类型，只要有问题的字段、构造函数或方法带有 @Autowired 注释。有关更多信息，请参阅 Using @Autowired。

In application components, you may also rely upon autowiring of the ResourceLoader as an alternative to implementing the ResourceLoaderAware interface. The traditional constructor and byType autowiring modes (as described in Autowiring Collaborators) are capable of providing a ResourceLoader for either a constructor argument or a setter method parameter, respectively. For more flexibility (including the ability to autowire fields and multiple parameter methods), consider using the annotation-based autowiring features. In that case, the ResourceLoader is autowired into a field, constructor argument, or method parameter that expects the ResourceLoader type as long as the field, constructor, or method in question carries the @Autowired annotation. For more information, see Using @Autowired.

要加载一个或多个 Resource 对象的资源路径，其中包含通配符或使用特殊的 classpath*: 资源前缀，请考虑让 ResourcePatternResolver 的实例自动装配到应用组件中，而不是 ResourceLoader 。

To load one or more Resource objects for a resource path that contains wildcards or makes use of the special classpath*: resource prefix, consider having an instance of ResourcePatternResolver autowired into your application components instead of ResourceLoader.

Resources as Dependencies

如果 bean 本身要通过某种动态过程来确定和提供资源路径，那么 bean 使用 ResourceLoader 或 ResourcePatternResolver 接口来加载资源可能是有道理的。例如，考虑加载某种模板，其中所需的特定资源取决于用户角色。如果资源是静态的，那么完全取消使用 ResourceLoader 接口（或 ResourcePatternResolver 接口）是有道理的，让 bean 公开它需要的 Resource 属性，并期望它们被注入到其中。

If the bean itself is going to determine and supply the resource path through some sort of dynamic process, it probably makes sense for the bean to use the ResourceLoader or ResourcePatternResolver interface to load resources. For example, consider the loading of a template of some sort, where the specific resource that is needed depends on the role of the user. If the resources are static, it makes sense to eliminate the use of the ResourceLoader interface (or ResourcePatternResolver interface) completely, have the bean expose the Resource properties it needs, and expect them to be injected into it.

使注入这些属性变得轻而易举的是，所有应用程序上下文都会注册并使用一个特殊的 JavaBeans PropertyEditor，它可以将 String 路径转换为 Resource 对象。例如，以下 MyBean 类有一个 template 属性，类型为 Resource。

What makes it trivial to then inject these properties is that all application contexts register and use a special JavaBeans PropertyEditor, which can convert String paths to Resource objects. For example, the following MyBean class has a template property of type Resource.

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  • Kotlin

public class MyBean {

	private Resource template;

	public setTemplate(Resource template) {
		this.template = template;
	}

	// ...
}
class MyBean(var template: Resource)

在 XML 配置文件中，template 属性可以使用该资源的简单字符串进行配置，如下例所示：

In an XML configuration file, the template property can be configured with a simple string for that resource, as the following example shows:

<bean id="myBean" class="example.MyBean">
	<property name="template" value="some/resource/path/myTemplate.txt"/>
</bean>

请注意，资源路径没有前缀。因此，由于应用程序上下文本身将用作 ResourceLoader，因此该资源将通过 ClassPathResource、FileSystemResource 或 ServletContextResource 加载，具体取决于应用程序上下文的具体类型。

Note that the resource path has no prefix. Consequently, because the application context itself is going to be used as the ResourceLoader, the resource is loaded through a ClassPathResource, a FileSystemResource, or a ServletContextResource, depending on the exact type of the application context.

如果你需要强制使用特定的 Resource 类型，则可以使用前缀。以下两个示例展示了如何强制使用 ClassPathResource 和 UrlResource（后者用于访问文件系统中的文件）：

If you need to force a specific Resource type to be used, you can use a prefix. The following two examples show how to force a ClassPathResource and a UrlResource (the latter being used to access a file in the filesystem):

<property name="template" value="classpath:some/resource/path/myTemplate.txt">
<property name="template" value="file:///some/resource/path/myTemplate.txt"/>

如果 MyBean 类被重构以与注释驱动的配置一起使用，则 myTemplate.txt 的路径可以存储在名为 template.path 的键下——例如，在为 Spring Environment 提供的属性文件中（参见 Environment Abstraction ）。然后可以通过使用属性占位符（请参见 Using @Value）通过 @Value 注释来引用模板路径。Spring 会将模板路径的值检出为字符串，并且特殊的 PropertyEditor 将把字符串转换为要注入到 MyBean 构造函数中的 Resource 对象。以下示例演示了如何实现这一点。

If the MyBean class is refactored for use with annotation-driven configuration, the path to myTemplate.txt can be stored under a key named template.path — for example, in a properties file made available to the Spring Environment (see Environment Abstraction). The template path can then be referenced via the @Value annotation using a property placeholder (see Using @Value). Spring will retrieve the value of the template path as a string, and a special PropertyEditor will convert the string to a Resource object to be injected into the MyBean constructor. The following example demonstrates how to achieve this.

  • Java

  • Kotlin

@Component
public class MyBean {

	private final Resource template;

	public MyBean(@Value("${template.path}") Resource template) {
		this.template = template;
	}

	// ...
}
@Component
class MyBean(@Value("\${template.path}") private val template: Resource)

如果我们希望支持在 classpath 中多个位置发现多个模板——例如，在 classpath 中的多个 jar 中——我们可以使用特殊 classpath*: 前缀和通配符将 templates.path 键定义为 classpath*:/config/templates/*.txt。如果我们重新定义 MyBean 类如下所示，Spring 会将模板路径模式转换为可以注入到 MyBean 构造函数中的 Resource 对象数组。

If we want to support multiple templates discovered under the same path in multiple locations in the classpath — for example, in multiple jars in the classpath — we can use the special classpath*: prefix and wildcarding to define a templates.path key as classpath*:/config/templates/*.txt. If we redefine the MyBean class as follows, Spring will convert the template path pattern into an array of Resource objects that can be injected into the MyBean constructor.

  • Java

  • Kotlin

@Component
public class MyBean {

	private final Resource[] templates;

	public MyBean(@Value("${templates.path}") Resource[] templates) {
		this.templates = templates;
	}

	// ...
}
@Component
class MyBean(@Value("\${templates.path}") private val templates: Resource[])

Application Contexts and Resource Paths

本节介绍如何使用资源创建应用程序上下文，包括使用 XML 的快捷方式、如何使用通配符以及其他详细信息。

This section covers how to create application contexts with resources, including shortcuts that work with XML, how to use wildcards, and other details.

Constructing Application Contexts

应用程序上下文构造函数（对于特定的应用程序上下文类型）通常使用字符串或字符串数组作为资源（例如构成上下文定义的 XML 文件）的位置路径。

An application context constructor (for a specific application context type) generally takes a string or array of strings as the location paths of the resources, such as XML files that make up the definition of the context.

如果这样的位置路径没有前缀，则从该路径构建并用于加载 bean 定义的特定 Resource 类型取决于特定应用程序上下文，并且适合该上下文。例如，考虑以下示例，它创建了一个 ClassPathXmlApplicationContext：

When such a location path does not have a prefix, the specific Resource type built from that path and used to load the bean definitions depends on and is appropriate to the specific application context. For example, consider the following example, which creates a ClassPathXmlApplicationContext:

  • Java

  • Kotlin

ApplicationContext ctx = new ClassPathXmlApplicationContext("conf/appContext.xml");
val ctx = ClassPathXmlApplicationContext("conf/appContext.xml")

bean 定义从 classpath 加载，因为使用了 ClassPathResource。但是，考虑以下示例，它创建了一个 FileSystemXmlApplicationContext：

The bean definitions are loaded from the classpath, because a ClassPathResource is used. However, consider the following example, which creates a FileSystemXmlApplicationContext:

  • Java

  • Kotlin

ApplicationContext ctx =
	new FileSystemXmlApplicationContext("conf/appContext.xml");
val ctx = FileSystemXmlApplicationContext("conf/appContext.xml")

现在，bean 定义从文件系统位置加载（在本例中，相对于当前工作目录）。

Now the bean definitions are loaded from a filesystem location (in this case, relative to the current working directory).

请注意，在位置路径上使用特殊 classpath 前缀或标准 URL 前缀会覆盖创建用于加载 bean 定义的默认 Resource 类型。考虑以下示例：

Note that the use of the special classpath prefix or a standard URL prefix on the location path overrides the default type of Resource created to load the bean definitions. Consider the following example:

  • Java

  • Kotlin

ApplicationContext ctx =
	new FileSystemXmlApplicationContext("classpath:conf/appContext.xml");
val ctx = FileSystemXmlApplicationContext("classpath:conf/appContext.xml")

使用 FileSystemXmlApplicationContext 从 classpath 加载 bean 定义。但是，它仍然是 FileSystemXmlApplicationContext。如果随后将其用作 ResourceLoader，那么任何没有前缀的路径仍然会被视为文件系统路径。

Using FileSystemXmlApplicationContext loads the bean definitions from the classpath. However, it is still a FileSystemXmlApplicationContext. If it is subsequently used as a ResourceLoader, any unprefixed paths are still treated as filesystem paths.

Constructing ClassPathXmlApplicationContext Instances — Shortcuts

ClassPathXmlApplicationContext 公开了多个构造函数，以实现方便的实例化。基本思想是你可以提供一个只包含 XML 文件本身的文件名（没有前导路径信息）的字符串数组，还可以提供一个 Class。然后，ClassPathXmlApplicationContext 从提供的类派生出路径信息。

The ClassPathXmlApplicationContext exposes a number of constructors to enable convenient instantiation. The basic idea is that you can supply merely a string array that contains only the filenames of the XML files themselves (without the leading path information) and also supply a Class. The ClassPathXmlApplicationContext then derives the path information from the supplied class.

考虑以下目录布局：

Consider the following directory layout:

com/ example/ services.xml repositories.xml MessengerService.class

以下示例展示了如何实例化一个 ClassPathXmlApplicationContext 实例，该实例由名为 services.xml 和 repositories.xml（位于 classpath 中）的文件中定义的 bean 组成：

The following example shows how a ClassPathXmlApplicationContext instance composed of the beans defined in files named services.xml and repositories.xml (which are on the classpath) can be instantiated:

  • Java

  • Kotlin

ApplicationContext ctx = new ClassPathXmlApplicationContext(
	new String[] {"services.xml", "repositories.xml"}, MessengerService.class);
val ctx = ClassPathXmlApplicationContext(arrayOf("services.xml", "repositories.xml"), MessengerService::class.java)

请参阅 ClassPathXmlApplicationContext javadoc 以了解有关各种构造函数的详情。

See the ClassPathXmlApplicationContext javadoc for details on the various constructors.

Wildcards in Application Context Constructor Resource Paths

应用程序上下文构造函数值中的资源路径可以是简单的路径（如前面所示），每个路径与目标`Resource`一一对应，或者包含特殊的`classpath*:`前缀或内部 Ant 风格模式（通过使用 Spring 的`PathMatcher`实用程序进行匹配）。后两者实际上都是通配符。

The resource paths in application context constructor values may be simple paths (as shown earlier), each of which has a one-to-one mapping to a target Resource or, alternately, may contain the special classpath*: prefix or internal Ant-style patterns (matched by using Spring’s PathMatcher utility). Both of the latter are effectively wildcards.

使用此机制的一种情况是需要执行组件式应用程序程序集的时候。所有组件都可以将上下文定义片段“发布”到已知的位置路径，并且当使用带有`classpath*:`前缀的相同路径创建最终的应用程序上下文时，将自动选取所有组件片段。

One use for this mechanism is when you need to do component-style application assembly. All components can publish context definition fragments to a well-known location path, and, when the final application context is created using the same path prefixed with classpath*:, all component fragments are automatically picked up.

请注意，此通配符特定于应用程序上下文中使用资源路径（或直接使用`PathMatcher`实用程序类层次结构），并在构建时解析。它与`Resource`类型本身无关。无法使用`classpath*:`前缀来构建实际的`Resource`，因为资源一次只指向一个资源。

Note that this wildcarding is specific to the use of resource paths in application context constructors (or when you use the PathMatcher utility class hierarchy directly) and is resolved at construction time. It has nothing to do with the Resource type itself. You cannot use the classpath*: prefix to construct an actual Resource, as a resource points to just one resource at a time.

Ant-style Patterns

路径位置可以包含 Ant 风格模式，如下例所示：

Path locations can contain Ant-style patterns, as the following example shows:

/WEB-INF/-context.xml com/mycompany//applicationContext.xml file:C:/some/path/-context.xml classpath:com/mycompany//applicationContext.xml

当路径位置包含 Ant 风格模式时，解析器将遵循一个更复杂的程序来尝试解析通配符。它会为该路径（直到最后一个非通配符段）生成`Resource`，并从中获取 URL。如果此 URL 不是`jar:`URL 或特定于容器的变体（例如 WebLogic 中的`zip:`、WebSphere 中的`wsjar`等），将从该 URL 获取`java.io.File`并用它来遍历文件系统以解析通配符。对于 jar URL，解析器要么从中获取`java.net.JarURLConnection`，要么手动解析 jar URL，然后遍历 jar 文件的内容以解析通配符。

When the path location contains an Ant-style pattern, the resolver follows a more complex procedure to try to resolve the wildcard. It produces a Resource for the path up to the last non-wildcard segment and obtains a URL from it. If this URL is not a jar: URL or container-specific variant (such as zip: in WebLogic, wsjar in WebSphere, and so on), a java.io.File is obtained from it and used to resolve the wildcard by traversing the filesystem. In the case of a jar URL, the resolver either gets a java.net.JarURLConnection from it or manually parses the jar URL and then traverses the contents of the jar file to resolve the wildcards.

Implications on Portability

如果指定路径已经是`file`URL（隐式是因为基本`ResourceLoader`是文件系统资源加载器或显式），则保证以完全可移植的方式使用通配符。

If the specified path is already a file URL (either implicitly because the base ResourceLoader is a filesystem one or explicitly), wildcarding is guaranteed to work in a completely portable fashion.

如果指定路径是`classpath`位置，则解析器必须通过进行`Classloader.getResource()调用来获取最后一个非通配符路径段的 URL。由于这只是路径的一个节点（而不是末尾的文件），因此实际上是未定义的（在`ClassLoader`javadoc 中），在这种情况下将返回哪种类型的 URL。实际上，它始终是表示目录的`java.io.File（其中类路径资源解析到文件系统位置）或某种 jar URL（其中类路径资源解析到 jar 位置）。尽管如此，此操作仍存在可移植性问题。

If the specified path is a classpath location, the resolver must obtain the last non-wildcard path segment URL by making a Classloader.getResource() call. Since this is just a node of the path (not the file at the end), it is actually undefined (in the ClassLoader javadoc) exactly what sort of a URL is returned in this case. In practice, it is always a java.io.File representing the directory (where the classpath resource resolves to a filesystem location) or a jar URL of some sort (where the classpath resource resolves to a jar location). Still, there is a portability concern on this operation.

如果为最后一个非通配符段获取 jar URL，则解析器必须能够从中获取`java.net.JarURLConnection`或手动解析 jar URL，以便能够遍历 jar 的内容并解析通配符。这在大多数环境中有效，但在其他环境中会失败，我们强烈建议在依赖它之前彻底测试来自 jar 的资源的通配符解析。

If a jar URL is obtained for the last non-wildcard segment, the resolver must be able to get a java.net.JarURLConnection from it or manually parse the jar URL, to be able to walk the contents of the jar and resolve the wildcard. This does work in most environments but fails in others, and we strongly recommend that the wildcard resolution of resources coming from jars be thoroughly tested in your specific environment before you rely on it.

The classpath*: Prefix

构建基于 XML 的应用程序上下文时，位置字符串可以使用特殊的`classpath*:`前缀，如下例所示：

When constructing an XML-based application context, a location string may use the special classpath*: prefix, as the following example shows:

  • Java

  • Kotlin

ApplicationContext ctx =
	new ClassPathXmlApplicationContext("classpath*:conf/appContext.xml");
val ctx = ClassPathXmlApplicationContext("classpath*:conf/appContext.xml")

此特殊前缀指定必须获取所有与给定名称匹配的类路径资源（在内部，这本质上是通过调用`ClassLoader.getResources(…​)`实现的），然后合并以形成最终的应用程序上下文定义。

This special prefix specifies that all classpath resources that match the given name must be obtained (internally, this essentially happens through a call to ClassLoader.getResources(…​)) and then merged to form the final application context definition.

通配符类路径依赖于基础 ClassLoader 的 getResources() 方法。现如今大多数应用服务器都提供自己的 ClassLoader 实现，因此行为可能不同，尤其是在处理 jar 文件时。检查 classpath* 是否有效的一个简单测试是使用 ClassLoader 从类路径上的 jar 文件中加载一个文件：getClass().getClassLoader().getResources("<someFileInsideTheJar>")。尝试使用同名但位于两个不同位置的文件进行此测试——例如，类路径上不同 jar 中的同名同路径文件。如果返回不恰当的结果，请查看应用服务器说明以了解可能影响 ClassLoader 行为的设置。

The wildcard classpath relies on the getResources() method of the underlying ClassLoader. As most application servers nowadays supply their own ClassLoader implementation, the behavior might differ, especially when dealing with jar files. A simple test to check if classpath* works is to use the ClassLoader to load a file from within a jar on the classpath: getClass().getClassLoader().getResources("<someFileInsideTheJar>"). Try this test with files that have the same name but reside in two different locations — for example, files with the same name and same path but in different jars on the classpath. In case an inappropriate result is returned, check the application server documentation for settings that might affect the ClassLoader behavior.

您还可以将`classpath*:`前缀与位置路径的其余部分中的`PathMatcher`模式结合使用（例如，classpath*:META-INF/*-beans.xml）。在这种情况下，解析策略非常简单：对最后一个非通配符路径段使用`ClassLoader.getResources()`调用以获取类加载器层次结构中的所有匹配的资源，然后对每个资源均使用前面描述的相同`PathMatcher`解析策略进行通配符子路径解析。

You can also combine the classpath*: prefix with a PathMatcher pattern in the rest of the location path (for example, classpath*:META-INF/*-beans.xml). In this case, the resolution strategy is fairly simple: A ClassLoader.getResources() call is used on the last non-wildcard path segment to get all the matching resources in the class loader hierarchy and then, off each resource, the same PathMatcher resolution strategy described earlier is used for the wildcard subpath.

Other Notes Relating to Wildcards

请注意，`classpath*:`在与 Ant 风格模式结合使用时，仅在模式开始之前至少有一个根目录时才能可靠地工作，除非实际目标文件驻留在文件系统中。这意味着这样的模式`classpath*:*.xml`可能无法从 jar 文件的根目录检索文件，而只能从已展开目录的根目录检索文件。

Note that classpath*:, when combined with Ant-style patterns, only works reliably with at least one root directory before the pattern starts, unless the actual target files reside in the file system. This means that a pattern such as classpath*:*.xml might not retrieve files from the root of jar files but rather only from the root of expanded directories.

Spring 检索类路径条目的能力源自 JDK 的`ClassLoader.getResources()`方法，该方法仅为一个空字符串（表示要搜索的潜在根目录）返回文件系统位置。Spring 还评估`URLClassLoader`运行时配置和 jar 文件中的`java.class.path`清单，但这并不能保证达到可移植行为。

Spring’s ability to retrieve classpath entries originates from the JDK’s ClassLoader.getResources() method, which only returns file system locations for an empty string (indicating potential roots to search). Spring evaluates URLClassLoader runtime configuration and the java.class.path manifest in jar files as well, but this is not guaranteed to lead to portable behavior.

类路径包的扫描需要类路径中存在相应的目录项。使用 Ant 构建 JAR 时，请勿激活 JAR 任务的`files-only`开关。此外，类路径目录在某些环境中可能不会根据安全策略公开——例如 JDK 1.7.0_45 及更高版本上的独立应用程序 （这需要在清单中设置“受信任库”。请参阅 https://stackoverflow.com/questions/19394570/java-jre-7u45-breaks-classloader-getresources）。

The scanning of classpath packages requires the presence of corresponding directory entries in the classpath. When you build JARs with Ant, do not activate the files-only switch of the JAR task. Also, classpath directories may not get exposed based on security policies in some environments — for example, stand-alone applications on JDK 1.7.0_45 and higher (which requires 'Trusted-Library' to be set up in your manifests. See https://stackoverflow.com/questions/19394570/java-jre-7u45-breaks-classloader-getresources).

在 JDK 9 的模块路径（Jigsaw）上，Spring 的类路径扫描通常按预期执行。在此处将资源放入专门的目录也强烈推荐，这样可以避免使用前面提到的可移植性问题搜索 jar 文件的根级别。

On JDK 9’s module path (Jigsaw), Spring’s classpath scanning generally works as expected. Putting resources into a dedicated directory is highly recommendable here as well, avoiding the aforementioned portability problems with searching the jar file root level.

如果要搜索的根包在多个类路径位置中可用，则使用`classpath:`资源的 Ant 风格模式并不能保证找到匹配的资源。考虑以下资源位置的示例：

Ant-style patterns with classpath: resources are not guaranteed to find matching resources if the root package to search is available in multiple classpath locations. Consider the following example of a resource location:

com/mycompany/package1/service-context.xml

现在考虑可能有人用来尝试查找该文件的 Ant 风格路径：

Now consider an Ant-style path that someone might use to try to find that file:

classpath:com/mycompany/**/service-context.xml

这样的资源可能只存在于类路径中的一个位置，但是当使用如前例所示的路径来尝试解析时，解析器以`getResource("com/mycompany");`返回的（第一个）URL 为依据。如果这个基本包节点存在于多个`ClassLoader`位置，则所需的资源可能不存在于找到的第一个位置。因此，在这种情况下，您应该更喜欢将`classpath*:`与相同的 Ant 风格模式一起使用，该模式搜索包含`com.mycompany`基本包的所有类路径位置： classpath*:com/mycompany/**/service-context.xml。

Such a resource may exist in only one location in the classpath, but when a path such as the preceding example is used to try to resolve it, the resolver works off the (first) URL returned by getResource("com/mycompany");. If this base package node exists in multiple ClassLoader locations, the desired resource may not exist in the first location found. Therefore, in such cases you should prefer using classpath*: with the same Ant-style pattern, which searches all classpath locations that contain the com.mycompany base package: classpath*:com/mycompany/**/service-context.xml.

FileSystemResource Caveats

没有附加FileSystemApplicationContext（换句话说，当FileSystemApplicationContext不是实际ResourceLoader）时，将FileSystemResource视为您预期的那样处理绝对和相对路径。相对路径相对于当前工作目录，而绝对路径相对于文件系统的根目录。

A FileSystemResource that is not attached to a FileSystemApplicationContext (that is, when a FileSystemApplicationContext is not the actual ResourceLoader) treats absolute and relative paths as you would expect. Relative paths are relative to the current working directory, while absolute paths are relative to the root of the filesystem.

然而，出于向后兼容性（历史）原因，当FileSystemApplicationContext是ResourceLoader时，这是改变的。FileSystemApplicationContext强制所有附加的FileSystemResource实例将所有位置路径视为相对，无论它们是否以前置斜线开头。实际上，这意味着以下示例是等效的：

For backwards compatibility (historical) reasons however, this changes when the FileSystemApplicationContext is the ResourceLoader. The FileSystemApplicationContext forces all attached FileSystemResource instances to treat all location paths as relative, whether they start with a leading slash or not. In practice, this means the following examples are equivalent:

  • Java

  • Kotlin

ApplicationContext ctx =
	new FileSystemXmlApplicationContext("conf/context.xml");
val ctx = FileSystemXmlApplicationContext("conf/context.xml")

  • Java

  • Kotlin

ApplicationContext ctx =
	new FileSystemXmlApplicationContext("/conf/context.xml");
val ctx = FileSystemXmlApplicationContext("/conf/context.xml")

以下示例也是等效的（即使它们看起来不同也会有道理，因为一个情况是相对的，而另一个情况是绝对的）：

The following examples are also equivalent (even though it would make sense for them to be different, as one case is relative and the other absolute):

  • Java

  • Kotlin

FileSystemXmlApplicationContext ctx = ...;
ctx.getResource("some/resource/path/myTemplate.txt");
val ctx: FileSystemXmlApplicationContext = ...
ctx.getResource("some/resource/path/myTemplate.txt")

  • Java

  • Kotlin

FileSystemXmlApplicationContext ctx = ...;
ctx.getResource("/some/resource/path/myTemplate.txt");
val ctx: FileSystemXmlApplicationContext = ...
ctx.getResource("/some/resource/path/myTemplate.txt")

实际上，如果您需要真正的绝对文件系统路径，则应避免将绝对路径与FileSystemResource或FileSystemXmlApplicationContext一起使用，并强制使用UrlResource，方法是使用file： URL 前缀。以下示例展示了如何执行此操作：

In practice, if you need true absolute filesystem paths, you should avoid using absolute paths with FileSystemResource or FileSystemXmlApplicationContext and force the use of a UrlResource by using the file: URL prefix. The following examples show how to do so:

  • Java

  • Kotlin

// actual context type doesn't matter, the Resource will always be UrlResource
ctx.getResource("file:///some/resource/path/myTemplate.txt");
// actual context type doesn't matter, the Resource will always be UrlResource
ctx.getResource("file:///some/resource/path/myTemplate.txt")

  • Java

  • Kotlin

// force this FileSystemXmlApplicationContext to load its definition via a UrlResource
ApplicationContext ctx =
	new FileSystemXmlApplicationContext("file:///conf/context.xml");
// force this FileSystemXmlApplicationContext to load its definition via a UrlResource
val ctx = FileSystemXmlApplicationContext("file:///conf/context.xml")