Spring JDBC - Read Query
以下示例将演示如何使用Spring JDBC读取查询。 我们将在学生表中阅读可用记录。
语法 (Syntax)
String selectQuery = "select * from Student";
List <Student> students = jdbcTemplateObject.query(selectQuery, new StudentMapper());
Where,
selectQuery - 选择查询以阅读学生。
jdbcTemplateObject - 用于从数据库中读取学生对象的StudentJDBCTemplate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。
要理解与Spring JDBC相关的上述概念，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。
| 步 | 描述 |
|---|---|
| 1 | 更新在Spring JDBC - First Application章节下创建的项目Student 。 |
| 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StudentDAO.java 。
package com.iowiki;
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.iowiki;
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.iowiki;
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StudentJDBCTemplate.java的实现类文件StudentJDBCTemplate.java 。
package com.iowiki;
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.iowiki;
import java.util.List;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.iowiki.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.iowiki.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
