（九）spring JDBC

为了使JDBC 更加易于使用，Spring 在JDBC API 上封装了一层模板JdbcTemplate。 JdbcTemplate 使用起来很简单：

1. 配置数据源, 如c3p0

2. 注册JdbcTemplate Bean：

3. 为Dao 注入添加JdbcTemplate 属性

<?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-4.2.xsd"> 
<!-- 配置注解自动扫描包 -->
<context:component-scan base-package="org.zgf.spring.dao"/>

<!-- 指定数据库配置文件位置 -->
<context:property-placeholder location="classpath:jdbc.properties"/>

<!-- 配置c3p0 数据源   -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="jdbcUrl" value="${jdbc.jdbcUrl}"/>
<property name="driverClass" value="${jdbc.driverClass}"/>
<property name="user" value="${jdbc.user}"/>
<property name="password" value="${jdbc.password}"/>
<property name="initialPoolSize" value="${jdbc.initialPoolSize}"/>
<property name="maxPoolSize" value="${jdbc.maxPoolSize}"/>
</bean>

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

</beans>

UserJTDao

/**
*  JdbcTemplate
*  1. JdbcTemplate 是Spring 框架对jdbc 的一层封装
*  2. JdbcTemplate 查询时 只支持位置参数，不支持命名参数
*  3. JdbcTemplate 可以对结果集进行封装，但是不支持级联属性
*/
@Repository
public class UserJTDao {

@Autowired
private JdbcTemplate jdbcTemplate;

private final String tableName = " spring_jdbc_user ";

/** 执行 insert , update , delete 语句   */
public void addUser(User user){
String  sql = "insert into " + tableName + " values(null,?,?,?)";
this.jdbcTemplate.update(sql, user.getUsername(),user.getPassword(),user.getAge());
}

/*** 批量执行：insert, update, delete 语句   */
public void addBatchUser(List<User> users){
String  sql = "insert into  " + tableName + "  values(null,?,?,?)";
List<Object[]> batchArgs = new ArrayList<Object[]>();
for(int i=0; i<users.size();  i++){
Object[] objectArray = new Object[]{users.get(i).getUsername(), users.get(i).getPassword(), users.get(i).getAge()};
batchArgs.add(objectArray);
}
this.jdbcTemplate.batchUpdate(sql, batchArgs);
}

/** 查询单个对象,进行结果集封装  */
public User getUserById(Integer id){
String sql = "select * from " + tableName + " where id = ? ";
//结果集映射规则
RowMapper<User> rowMapper = new BeanPropertyRowMapper<>(User.class);
return this.jdbcTemplate.queryForObject(sql, rowMapper, id);
}

/**  查询列表   */
public List<User> getUsersByAge(int age){
String sql = "select * from " + tableName + " where age = ?" ;
//结果集映射方式
RowMapper<User> rowMapper = new BeanPropertyRowMapper<>(User.class);
return this.jdbcTemplate.query(sql, rowMapper, age);

}

/**  查询某一字段   */
public String getUserName(int id){
String sql = "select username from " + tableName + " where id = ? ";
return this.jdbcTemplate.queryForObject(sql, String.class, id);
}

/** 查询某一字段数组   */
public List<String> getUserNames(int age){
String sql = "select username from " + tableName + " where age = ?" ;
//结果集映射方式
return this.jdbcTemplate.queryForList(sql, String.class, age);
}
}

测试用例

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations="classpath:org/zgf/spring/dao/applications-template.xml")
public class Test_UserDao {

@Autowired
private UserJTDao userJTDao;

@Test
public void test_addUser(){
User user = new User("zong","gaofeng",20);
this.userJTDao.addUser(user);
}

@Test
public void test_addBatch(){
List<User> users = new ArrayList<>();
users.add(new User("zong_01","zong_01",30));
users.add(new User("zong_02","zong_03",30));
users.add(new User("zong_03","zong_03",30));

this.userJTDao.addBatchUser(users);
System.out.println("成功添加了" + users.size() + " 条记录");
}

@Test
public void test_getById(){
int id = 1;
User user = this.userJTDao.getUserById(id);
System.out.println(user);
}

@Test
public void test_getUsersByAge(){
List<User> userList = this.userJTDao.getUsersByAge(30);
for (User user : userList) {
System.out.println(user);
}
}

@Test
public void test_getUsernameById(){
int id = 10;
String username = this.userJTDao.getUserName(id);
System.out.println(username);
}

@Test
public void test_getUsernames(){
int age = 30;
List<String> usernames = this.userJTDao.getUserNames(age);
System.err.println("usernames:" + usernames);
}

}