Spring--JdbcTemplate

JdbcTemplate简介

为了使JDBC更加易于使用，Spring在JDBC API上定义了一个抽象层，以此建立一个JDBC存取框架

作为Spring JDBC框架的核心，JDBC模板的设计目的是为不同类型的JDBC操作提供模板方法，每个模板方法都能控制整个过程，并允许覆盖过程中的特定任务。通过这种方式，可以在尽可能保留灵活性的情况下，将数据库存取的工作量降到最低。

代码示例：

首先是数据库的配置。数据库中包含employee和department两张表。

jdbc.user=scott
jdbc.password=tiger
jdbc.driverClass=oracle.jdbc.driver.OracleDriver
jdbc.jdbcUrl=jdbc:oracle:thin:@localhost:1521:orcl

jdbc.initialPoolSize=5
jdbc.maxPoolSize=10

然后是spring的配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.1.xsd"> 
<context:component-scan base-package="com.yl.spring.jdbc"></context:component-scan>

<!-- 导入属性文件 -->
<context:property-placeholder location="classpath:db.properties"/>
<!-- 配置c3p0数据源 -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="user" value="${jdbc.user}"></property>
<property name="password" value="${jdbc.password}"></property>
<property name="driverClass" value="${jdbc.driverClass}"></property>
<property name="jdbcUrl" value="${jdbc.jdbcUrl}"></property>

<property name="initialPoolSize" value="${jdbc.initialPoolSize}"></property>
<property name="maxPoolSize" value="${jdbc.maxPoolSize}"></property>
</bean>

<!-- 配置Spring的JdbcTemplate -->
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
<property name="dataSource" ref="dataSource"></property>
</bean>
</beans>

然后是两个实体类:Employee和Department

package com.yl.spring.jdbc;

public class Employee {
private Integer id;
private String lastName;
private String email;

private Department department;

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getLastName() {
return lastName;
}

public void setLastName(String lastName) {
this.lastName = lastName;
}

public String getEmail() {
return email;
}

public void setEmail(String email) {
this.email = email;
}

public Department getDepartment() {
return department;
}

public void setDepartment(Department department) {
this.department = department;
}

@Override
public String toString() {
return "Employee [id=" + id + ", lastName=" + lastName + ", email="
+ email + ", department=" + department + "]";
}

}

package com.yl.spring.jdbc;

public class Department {
private Integer id;
private String name;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString() {
return "Department [id=" + id + ", name=" + name + "]";
}

}

然后是测试类

package com.yl.spring.jdbc;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import javax.sql.DataSource;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;

public class JDBCTest {

private ApplicationContext ctx = null;
private JdbcTemplate jdbcTemplate;
private EmployeeDao employeeDao;

{
ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
jdbcTemplate = (JdbcTemplate)ctx.getBean("jdbcTemplate");
employeeDao = ctx.getBean(EmployeeDao.class);
}

@Test
public void testEmployeeDao() {
System.out.println(employeeDao.get(1));
}

/**
* 获取单个列的值，或做统计查询
*/
@Test
public void testQueryForObject2() {
String sql = "SELECT count(id) FROM employee";
long count = jdbcTemplate.queryForObject(sql, Long.class);
System.out.println(count);
}

/**
* 查到实体类的集合
*/
@Test
public void testQueryForList() {
String sql = "SELECT id, last_name, email FROM employee WHERE id > ?";
RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<Employee>(Employee.class);
List<Employee> employees = jdbcTemplate.query(sql, rowMapper, 5);
System.out.println(employees);
}

/**
* 从数据库中获取一条记录，实际得到对应的一个对象
* 1.RowMapper指定如何映射结果集的行，常用的实现类为BeanPropertyRowMapper
* 2.使用SQL中列的别名完成列名和类的属性名的映射。例如last_name和lastName
* 3.不支持级联属性。JdbcTemplate到底是一个JDBC工具，不是ORM框架。
*/
@Test
public void TestForQueryObject() {
String sql = "SELECT id, last_name, email FROM employee WHERE id = ?";
RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<Employee>(Employee.class);

Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, 1);
System.out.println(employee);
}

/**
* 批量执行更新：批量的INSERT, UPDATE, DELETE
* 最后一个参数是Object[]的list类型：因为修改一条记录需要一个Object的数组，那么多条就是需要多个Object的数组
*/
@Test
public void testBatchUpdate() {
String sql = "INSERT INTO employee(id, last_name, email, dept_id) VALUES(?, ?, ?, ?)";
List<Object[]> batchArgs = new ArrayList<Object[]>();
batchArgs.add(new Object[]{6, "AA", "AA@163.com", 1});
batchArgs.add(new Object[]{7, "BB", "BB@163.com", 2});
batchArgs.add(new Object[]{8, "CC", "CC@163.com", 3});
batchArgs.add(new Object[]{9, "DD", "DD@163.com", 3});
batchArgs.add(new Object[]{10, "EE", "EE@163.com", 2});
jdbcTemplate.batchUpdate(sql, batchArgs);
}

/**
* 执行INSERT, UPDATE, DELETE
*/
@Test
public void testUpdate() {
String sql = "UPDATE employee SET last_name=? WHERE id=?";
jdbcTemplate.update(sql, "Jack", 5);
}

@Test
public void test() throws SQLException {
DataSource dataSource = (DataSource)ctx.getBean("dataSource");
System.out.println(dataSource.getConnection());
}

}

如果在项目中使用JdbcTemplate，那么可以参考下面的写法来写对应的dao：

package com.yl.spring.jdbc;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.stereotype.Repository;

@Repository
public class EmployeeDao {

@Autowired
private JdbcTemplate jdbcTemplate;

public Employee get(Integer id) {
String sql = "SELECT id, last_name, email FROM employee WHERE id = ?";
RowMapper<Employee> rowMapper = new BeanPropertyRowMapper<Employee>(Employee.class);

Employee employee = jdbcTemplate.queryForObject(sql, rowMapper, id);

return employee;
}
}