mybatis集成spring操作数据库（注解方式）

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这里以增删改查user table为例

1 首先导入相关的jar包文件，如下：

导入的包：commons- dbcp,commons-logging,commons-pool,mybatis-3.0.5,mybatis-spring,mysql-connector-java,spring,spring-aop,spring-beans,spring-context,spring-core,spring-expression,spring-tx

2 然后确定pojo对象，User.java

public class User implements Serializable {

private String username;
private String password;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}

3 用接口形式调用映射文件UserMapper.java

public interface UserMapper {

User getUser(String username);
User getUserList();
@Select("select * from User where username=#{username}")
User getUserAnnotation(String username);
}

4 书写操作数据库的sql语句，UserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.cienet.bjk.persistence.UserMapper">
<cache />
<select id="getUser" parameterType="string" resultType="User">
SELECT
* from user where username = #{username}
</select>
<select id="getUserList" resultType="list">
SELECT
* from user
</select>
</mapper>

代码解释：namespace为映射的interface文件的位置，这个必须和上面的UserMapper.xml文件放在同一个目录下，且名称要一样，不然会出现找不到文件的错误。

select标签中的id表示与UserMapper.java中的方法对应。

parameterType表示传入参数的类型，resultType表示返回结果的类型#{}表示传入参数。

5 业务逻辑层代码

@Service
public class UserService {

@Autowired
private UserMapper userMapper;
public User getUser(String username){
return userMapper.getUser(username);
}
public User getUserAnnotation(String username){
return userMapper.getUser(username);
}
@SuppressWarnings("unchecked")
public List<User> getUserList() {
return (List<User>) userMapper.getUserList();
}
}

6 然后在spring配置以注解方式运行，这样的好处是不用为每个pojo写对应的xml映射文件。

<?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"
xmlns:aop="http://www.springframework.org/schema/aop"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://www.springframework.org/schema/aop
http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
http://www.springframework.org/schema/tx
http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">

<bean
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations">
<value>classpath:com/cienet/bjk/config/jdbc.properties</value>
</property>
</bean>

7 最后，写测试代码进行验证是否运行成功。

@Test
public void testUsert1(){
ctx = new ClassPathXmlApplicationContext(
"com/cienet/bjk/config/beans.xml");
UserService user = (UserService) ctx.getBean("userService");
System.out.print(user.getUser("123").getPassword());
//System.out.print(user.getUserList().get(0).getPassword());
System.out.println(user.getUserAnnotation("123").getPassword());//invoke the annotation
UserMapper um = sqlSession.getMapper(UserMapper.class);
System.out.println(um.getUserAnnotation("123").getPassword());
}

运行成功最后。其中System.out.println(user.getUserAnnotation("123").getPassword());//invoke the annotation

表示用注解的方式访问访问数据库，这种形式允许直接把sql语句写在java文件中，不过，不推荐这种方式，因为java文件会过于臃肿，不好维护。

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