Mybatis增删改查

pom.xml

<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.3.1</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.34</version>
</dependency>

mybatis_config.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
     <environments default="development">
         <environment id="development">
             <transactionManager type="JDBC" />
             <!-- 配置数据库连接信息 -->
             <dataSource type="POOLED">
                 <property name="driver" value="com.mysql.jdbc.Driver" />
                 <property name="url" value="jdbc:mysql://localhost:3306/test" />
                 <property name="username" value="root" />
                 <property name="password" value="123456" />
             </dataSource>
         </environment>
     </environments>
     <mappers>
        <mapper resource="com/feige/Mapper/UserMapper.xml"/> 
     </mappers>
</configuration>

POJO类

public class User {    
    private int id;  
    private String name;   
    private String hobby;    
    private int age;
    ......setter、getter省略
}

SqlSessionUtill工具类

public class SqlSessionUtill {
    private final static Class<SqlSessionUtill> LOCK = SqlSessionUtill.class;
    private static SqlSessionFactory sqlSessionFactory = null;
    private SqlSessionUtill() {};
    public static SqlSessionFactory getSqlSessionFactory() {
        synchronized (LOCK) {
            if(sqlSessionFactory != null) {
                return sqlSessionFactory;
            }
            String resource = "mybatis_config.xml";
            InputStream inputStream;
            try {
                inputStream = Resources.getResourceAsStream(resource);
                sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }
           return sqlSessionFactory;
        }
    }
    public static SqlSession openSqlSession() {
        if(sqlSessionFactory == null) {
            getSqlSessionFactory();
        }
        return sqlSessionFactory.openSession();
    }
}

UserMapper.java

public interface UserMapper {
    User findUserById(int id) throws Exception;
    int deleteUserById(int id) throws Exception;
    int addUser(User user) throws Exception;
    int updateUser(User user) throws Exception;
}

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.feige.Mapper.UserMapper">
    <select id="findUserById" parameterType="int" resultType="com.feige.po.User">
        select * from user where id = #{id}
    </select>
    <delete id="deleteUserById"  parameterType="java.lang.Integer" >
        delete from user where id=#{value}
    </delete>
    <insert id="addUser" parameterType="com.feige.po.User" > 
        insert into user(id, name, hobby, age) value(#{id}, #{name}, #{hobby}, #{age}) 
    </insert>
    <update id="updateUser" parameterType="com.feige.po.User">
        update user set name=#{name}, hobby=#{hobby}, age=#{age} where id=#{id}
    </update>    
</mapper>

注：当参数是一个基本数据类型时，要用#{value}。statement的id属性要和接口的方法名对应。

Test.java

public class Test {
    public static void main(String[] args) throws Exception {
        SqlSession session = null;
        try {
            session = SqlSessionUtill.openSqlSession();
            UserMapper userMapper = session.getMapper(UserMapper.class);
            User user = new User();
            user.setId(2);
            user.setAge(11);
            user.setHobby("6666");
            user.setName("feige");
            int num = userMapper.updateUser(user);
            System.out.println("影响数据的条数："+num);
            session.commit();
        } finally {
            session.close();
        }
    }
}

注：SqlSession默认是开启事务且不自动提交的，增删改默认返回影响数据的条数。

开发规范

1、Mapper.java和Mapper.xml在同一个包下。
2、Mapper.java中的方法名字和Mapper.xml中statement的id一样。
3、Mapper.xml中的namespace等于Mapper.java的全限命名。
4、Mapper.java接口方法中输入的参数类型，和Mapper.xml中statement的paramterType指定类型一致。
5、Mapper.java接口方法中返回的参数类型，和Mapper.xml中statement的resultType(resultMap的映射类型)指定类型一致。