江南一点雨6. JdbcTemplate
JdbcTemplate 是 Spring 利用 Aop 思想封装的 JDBC 操作工具。
6.1 准备
创建一个新项目，添加如下依赖：
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>5.1.9.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.1.9.RELEASE</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.17</version>
</dependency>
</dependencies>
准备数据库：
CREATE DATABASE /*!32312 IF NOT EXISTS*/`test01` /*!40100 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci */ /*!80016 DEFAULT ENCRYPTION='N' */;
USE `test01`;
/*Table structure for table `user` */
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(255) COLLATE utf8mb4_general_ci DEFAULT NULL,
`address` varchar(255) COLLATE utf8mb4_general_ci DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci;
准备一个实体类：
public class User {
private Integer id;
private String username;
private String address;
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", address='" + address + '\'' +
'}';
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}
6.2 Java 配置
提供一个配置类，在配置类中配置 JdbcTemplate：
@Configuration
public class JdbcConfig {
@Bean
DataSource dataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
dataSource.setDriverClassName("com.mysql.cj.jdbc.Driver");
dataSource.setUsername("root");
dataSource.setPassword("123");
dataSource.setUrl("jdbc:mysql:///test01");
return dataSource;
}
@Bean
JdbcTemplate jdbcTemplate() {
return new JdbcTemplate(dataSource());
}
}
这里，提供两个 Bean，一个是 DataSource 的 Bean，另一个是 JdbcTemplate 的 Bean，JdbcTemplate 的配置非常容易，只需要 new 一个 Bean 出来，然后配置一下 DataSource 就i可以。
public class Main {
private JdbcTemplate jdbcTemplate;
@Before
public void before() {
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(JdbcConfig.class);
jdbcTemplate = ctx.getBean(JdbcTemplate.class);
}
@Test
public void insert() {
jdbcTemplate.update("insert into user (username,address) values (?,?);", "javaboy", "www.javaboy.org");
}
@Test
public void update() {
jdbcTemplate.update("update user set username=? where id=?", "javaboy123", 1);
}
@Test
public void delete() {
jdbcTemplate.update("delete from user where id=?", 2);
}
@Test
public void select() {
User user = jdbcTemplate.queryForObject("select * from user where id=?", new BeanPropertyRowMapper<User>(User.class), 1);
System.out.println(user);
}
}
在查询时，如果使用了 BeanPropertyRowMapper，要求查出来的字段必须和 Bean 的属性名一一对应。如果不一样，则不要使用 BeanPropertyRowMapper，此时需要自定义 RowMapper 或者给查询的字段取别名。
- 给查询出来的列取别名：
@Test
public void select2() {
User user = jdbcTemplate.queryForObject("select id,username as name,address from user where id=?", new BeanPropertyRowMapper<User>(User.class), 1);
System.out.println(user);
}
2.自定义 RowMapper
@Test
public void select3() {
User user = jdbcTemplate.queryForObject("select * from user where id=?", new RowMapper<User>() {
public User mapRow(ResultSet resultSet, int i) throws SQLException {
int id = resultSet.getInt("id");
String username = resultSet.getString("username");
String address = resultSet.getString("address");
User u = new User();
u.setId(id);
u.setName(username);
u.setAddress(address);
return u;
}
}, 1);
System.out.println(user);
}
查询多条记录，方式如下：
@Test
public void select4() {
List<User> list = jdbcTemplate.query("select * from user", new BeanPropertyRowMapper<>(User.class));
System.out.println(list);
}
6.3 XML 配置
以上配置，也可以通过 XML 文件来实现。通过 XML 文件实现只是提供 JdbcTemplate 实例，剩下的代码还是 Java 代码，就是 JdbcConfig 被 XML 文件代替而已。
<bean class="org.springframework.jdbc.datasource.DriverManagerDataSource" id="dataSource">
<property name="username" value="root"/>
<property name="password" value="123"/>
<property name="url" value="jdbc:mysql:///test01?serverTimezone=Asia/Shanghai"/>
<property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/>
</bean>
<bean class="org.springframework.jdbc.core.JdbcTemplate" id="jdbcTemplate">
<property name="dataSource" ref="dataSource"/>
</bean>
配置完成后，加载该配置文件，并启动：
public class Main {
private JdbcTemplate jdbcTemplate;
@Before
public void before() {
ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
jdbcTemplate = ctx.getBean(JdbcTemplate.class);
}
@Test
public void insert() {
jdbcTemplate.update("insert into user (username,address) values (?,?);", "javaboy", "www.javaboy.org");
}
@Test
public void update() {
jdbcTemplate.update("update user set username=? where id=?", "javaboy123", 1);
}
@Test
public void delete() {
jdbcTemplate.update("delete from user where id=?", 2);
}
@Test
public void select() {
User user = jdbcTemplate.queryForObject("select * from user where id=?", new BeanPropertyRowMapper<User>(User.class), 1);
System.out.println(user);
}
@Test
public void select4() {
List<User> list = jdbcTemplate.query("select * from user", new BeanPropertyRowMapper<>(User.class));
System.out.println(list);
}
@Test
public void select2() {
User user = jdbcTemplate.queryForObject("select id,username as name,address from user where id=?", new BeanPropertyRowMapper<User>(User.class), 1);
System.out.println(user);
}
@Test
public void select3() {
User user = jdbcTemplate.queryForObject("select * from user where id=?", new RowMapper<User>() {
public User mapRow(ResultSet resultSet, int i) throws SQLException {
int id = resultSet.getInt("id");
String username = resultSet.getString("username");
String address = resultSet.getString("address");
User u = new User();
u.setId(id);
u.setName(username);
u.setAddress(address);
return u;
}
}, 1);
System.out.println(user);
}
}
