The `FieldSet`

在 Spring Batch 中处理平面文件时，无论其是输入还是输出，最重要的类之一是 FieldSet。许多架构和库包含有助于您从文件中读取的抽象，但它们通常返回 String 或 String 对象数组。这实际上只让您完成了任务的一半。FieldSet 是 Spring Batch 的抽象，用于启用对文件资源中字段的绑定。它允许开发人员以与处理数据库输入相同的方式使用文件输入。FieldSet 在概念上类似于 JDBC ResultSet。FieldSet 只需要一个参数：令牌的 String 数组。您还可以选择配置字段的名称，以便可以通过索引或名称访问字段，就像 ResultSet 中的模式一样，如下面的示例所示：

When working with flat files in Spring Batch, regardless of whether it is for input or output, one of the most important classes is the FieldSet. Many architectures and libraries contain abstractions for helping you read in from a file, but they usually return a String or an array of String objects. This really only gets you halfway there. A FieldSet is Spring Batch’s abstraction for enabling the binding of fields from a file resource. It allows developers to work with file input in much the same way as they would work with database input. A FieldSet is conceptually similar to a JDBC ResultSet. A FieldSet requires only one argument: a String array of tokens. Optionally, you can also configure the names of the fields so that the fields may be accessed either by index or name as patterned after ResultSet, as shown in the following example:

String[] tokens = new String[]{"foo", "1", "true"};
FieldSet fs = new DefaultFieldSet(tokens);
String name = fs.readString(0);
int value = fs.readInt(1);
boolean booleanValue = fs.readBoolean(2);

FieldSet 接口上有更多选项，例如 Date、long、BigDecimal 等。FieldSet 的最大优势在于它可以提供平面文件输入的一致性解析。它不会以可能出乎意料的方式在每个批处理作业中进行不同的解析，而是可以保持一致，无论是在处理格式异常导致的错误，还是在进行简单数据转换时。

There are many more options on the FieldSet interface, such as Date, long, BigDecimal, and so on. The biggest advantage of the FieldSet is that it provides consistent parsing of flat file input. Rather than each batch job parsing differently in potentially unexpected ways, it can be consistent, both when handling errors caused by a format exception, or when doing simple data conversions.

The FieldSet

The `FieldSet`