org.springframework.jdbc.core.JdbcTemplate 类是JDBC核心包中的中心类.它简化了JDBC的使用，有助于避免常见错误.它执行核心JDBC工作流，让应用程序代码提供SQL并提取结果.此类执行SQL查询或更新，启动对ResultSet的迭代并捕获JDBC异常并将它们转换为 org.springframework.dao 包中定义的通用的，更具信息性的异常层次结构.
以下是org.springframework.jdbc.core.JdbcTemplate类的声明 :
public class JdbcTemplate extends JdbcAccessor implements JdbcOperations
第1步 : 使用已配置的数据源创建JdbcTemplate对象.
步骤2 : 使用JdbcTemplate对象方法进行数据库操作.
以下示例将演示如何使用JdbcTemplate类读取查询.我们将读取学生表中的可用记录.
String selectQuery = "select * from Student"; List <Student> students = jdbcTemplateObject.query(selectQuery, new StudentMapper());
其中，
selectQuery : 选择查询以阅读学生.
jdbcTemplateObject : StudentJDBCTemplate对象从数据库中读取学生对象.
StudentMapper : StudentMapper是一个RowMapper对象，用于将每个读取的记录映射到学生对象.
要理解上述与Spring JDBC相关的概念，让我们编写一个选择查询的示例.要编写我们的示例，让我们使用一个可用的Eclipse IDE并使用以下步骤创建一个Spring应用程序.
| Step | 描述 |
|---|---|
| 1 | 更新在章节下创建的项目学生Spring JDBC - First Application . |
| 2 | 更新bean配置并运行应用程序，如下所述. |
以下是数据访问对象接口文件的内容 StudentDAO.java .
package com.it1352;
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
* all the records from the Student table.
*/
public List<Student> listStudents();
}以下是 Student.java 文件的内容.
package com.it1352;
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 StudentMapper.java 文件的内容.
package com.it1352;
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;
}
}以下是定义的DAO接口StudentDAO的实现类文件 StudentJDBCTemplate.java .
package com.it1352;
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 List<Student> listStudents() {
String SQL = "select * from Student";
List <Student> students = jdbcTemplateObject.query(SQL, new StudentMapper());
return students;
}
}以下是 MainApp.java 文件的内容.
package com.it1352;
import java.util.List;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.it1352.StudentJDBCTemplate;
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
StudentJDBCTemplate studentJDBCTemplate =
(StudentJDBCTemplate)context.getBean("studentJDBCTemplate");
System.out.println("------Listing Multiple Records--------" );
List<Student> students = studentJDBCTemplate.listStudents();
for (Student record : students) {
System.out.print("ID : " + record.getId() );
System.out.print(", Name : " + record.getName() );
System.out.println(", Age : " + record.getAge());
}
}
}以下是配置文件 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.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.IT屋.StudentJDBCTemplate"> <property name = "dataSource" ref = "dataSource" /> </bean> </beans>
完成源和bean配置文件的创建后，让我们运行应用程序.如果您的应用程序一切正常，它将打印以下消息.
------Listing Multiple Records-------- ID : 1, Name : Zara, Age : 11 ID : 2, Name : Nuha, Age : 2 ID : 3, Name : Ayan, Age : 15
