Springjdbc 简明教程

PreparedStatementSetter Interface

org.springframework.jdbc.core.PreparedStatementSetter 接口充当由 JdbcTemplate 类使用的通用回调接口。此接口对 JdbcTemplate 类提供的 PreparedStatement（对于使用相同 SQL 的批量中的每个更新）中的每个更新设置值。

The org.springframework.jdbc.core.PreparedStatementSetter interface acts as a general callback interface used by the JdbcTemplate class. This interface sets values on a PreparedStatement provided by the JdbcTemplate class, for each of a number of updates in a batch using the same SQL.

实现负责设置所有必需的参数。带有占位符的 SQL 已经提供。使用此接口比使用 PreparedStatementCreator 更容易。JdbcTemplate 将创建 PreparedStatement，回调仅负责设置参数值。

Implementations are responsible for setting any necessary parameters. SQL with placeholders will already have been supplied. It’s easier to use this interface than PreparedStatementCreator. The JdbcTemplate will create the PreparedStatement, with the callback only being responsible for setting parameter values.

Interface Declaration

以下是 org.springframework.jdbc.core.PreparedStatementSetter 接口的声明——

Following is the declaration for org.springframework.jdbc.core.PreparedStatementSetter interface −

public interface PreparedStatementSetter

Usage

Step 1 − Create a JdbcTemplate object using a configured datasource.
Step 2 − Use JdbcTemplate object methods to make database operations while passing PreparedStatementSetter object to replace place holders in query.

Example

以下示例将演示如何使用 JdbcTemplate 类和 PreparedStatementSetter 接口读取查询。我们将读取学生表中可用的学生记录。

Following example will demonstrate how to read a query using JdbcTemplate class and PreparedStatementSetter interface. We’ll read available record of a student in Student Table.

Syntax

final String SQL = "select * from Student where id = ? ";
List <Student> students = jdbcTemplateObject.query(
   SQL, new PreparedStatementSetter() {

   public void setValues(PreparedStatement preparedStatement) throws SQLException {
      preparedStatement.setInt(1, id);
   }
},
new StudentMapper());

其中，

Where,

SQL − Select query to read students.
jdbcTemplateObject − StudentJDBCTemplate object to read student object from database.
PreparedStatementSetter − PreparedStatementSetter object to set parameters in query.
StudentMapper − StudentMapper is a RowMapper object to map each fetched record to student object.

为了理解与 Spring JDBC 相关的上述概念，我们编写一个将选择一个查询的示例。为了编写我们的示例，让我们有一个可用的 Eclipse IDE 并使用以下步骤创建一个 Spring 应用程序。

To understand the above-mentioned concepts related to Spring JDBC, let us write an example which will select a query. To write our example, let us have a working Eclipse IDE in place and use the following steps to create a Spring application.

Step

Description

Update the project Student created under chapter Spring JDBC - First Application.

Update the bean configuration and run the application as explained below.

以下是对数据访问对象接口文件 StudentDAO.java 的内容。

Following is the content of the Data Access Object interface file StudentDAO.java.

package com.tutorialspoint;

import java.util.List;
import javax.sql.DataSource;

public interface StudentDAO {
   /**
      * This is the method to be used to initialize
      * database resources ie. connection.
   */
   public void setDataSource(DataSource ds);

   /**
      * This is the method to be used to list down
      * a record from the Student table corresponding
      * to a passed student id.
   */
   public Student getStudent(Integer id);
}

以下是 Student.java 文件的内容。

Following is the content of the Student.java file.

package com.tutorialspoint;

public class Student {
   private Integer age;
   private String name;
   private Integer id;

   public void setAge(Integer age) {
      this.age = age;
   }
   public Integer getAge() {
      return age;
   }
   public void setName(String name) {
      this.name = name;
   }
   public String getName() {
      return name;
   }
   public void setId(Integer id) {
      this.id = id;
   }
   public Integer getId() {
      return id;
   }
}

以下是对 StudentMapper.java 文件的内容。

Following is the content of the StudentMapper.java file.

package com.tutorialspoint;

import java.sql.ResultSet;
import java.sql.SQLException;
import org.springframework.jdbc.core.RowMapper;

public class StudentMapper implements RowMapper<Student> {
   public Student mapRow(ResultSet rs, int rowNum) throws SQLException {
      Student student = new Student();
      student.setId(rs.getInt("id"));
      student.setName(rs.getString("name"));
      student.setAge(rs.getInt("age"));
      return student;
   }
}

以下是对所定义的 DAO 接口 StudentDAO 实现的类文件 StudentJDBCTemplate.java 。

Following is the implementation class file StudentJDBCTemplate.java for the defined DAO interface StudentDAO.

package com.tutorialspoint;

import java.util.List;
import javax.sql.DataSource;
import org.springframework.jdbc.core.JdbcTemplate;

public class StudentJDBCTemplate implements StudentDAO {
   private DataSource dataSource;
   private JdbcTemplate jdbcTemplateObject;

   public void setDataSource(DataSource dataSource) {
      this.dataSource = dataSource;
      this.jdbcTemplateObject = new JdbcTemplate(dataSource);
   }
   public Student getStudent(final Integer id) {
      final String SQL = "select * from Student where id = ? ";
      List <Student> students = jdbcTemplateObject.query(
         SQL, new PreparedStatementSetter() {
            public void setValues(PreparedStatement preparedStatement) throws SQLException {
               preparedStatement.setInt(1, id);
            }
         },
         new StudentMapper()
      );
      return students.get(0);
   }
}

以下是 MainApp.java 文件的内容。

Following is the content of the MainApp.java file.

package com.tutorialspoint;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainApp {
   public static void main(String[] args) {
      ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
      StudentJDBCTemplate studentJDBCTemplate = (StudentJDBCTemplate)context.getBean("studentJDBCTemplate");
      Student student = studentJDBCTemplate.getStudent(1);
      System.out.print("ID : " + student.getId() );
      System.out.println(", Age : " + student.getAge());
   }
}

以下是配置文件 Beans.xml 。

Following is the configuration file Beans.xml.

<?xml version = "1.0" encoding = "UTF-8"?>
<beans xmlns = "http://www.springframework.org/schema/beans"
   xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation = "http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd ">

   <!-- Initialization for data source -->
   <bean id = "dataSource"
      class = "org.springframework.jdbc.datasource.DriverManagerDataSource">
      <property name = "driverClassName" value = "com.mysql.cj.jdbc.Driver"/>
      <property name = "url" value = "jdbc:mysql://localhost:3306/TEST"/>
      <property name = "username" value = "root"/>
      <property name = "password" value = "admin"/>
   </bean>

   <!-- Definition for studentJDBCTemplate bean -->
   <bean id = "studentJDBCTemplate"
      class = "com.tutorialspoint.StudentJDBCTemplate">
      <property name = "dataSource" ref = "dataSource" />
   </bean>
</beans>

一旦您完成创建源代码和 bean 配置文件，让我们运行此应用程序。如果应用程序一切正常，它将打印以下信息。

Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message.

ID : 1, Age : 17