Mybatis-自定义类型处理器

类型转换器：mybatis中有一些常用的类型转换器，比如把Java中的short类型转换为mysql中的short类型；但是如果现在是Java中的Date类型，但是我想要存储到数据库中转换为Long类型的毫秒值（默认1970-00-00-00至今）,就需要自己定义转换器

1.创建实体类User

public class User {

    private int id;
    private String username;
    private String password;
    private Date birthday;

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    public int getId() {
        return id;
    }

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

    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;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}

2.编写UserMapper.xml文件

<?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.hao.mapper.UserMapper">

    <insert id="save" parameterType="user">
        insert into user values(#{id},#{username},#{password},#{birthday})
    </insert>
</mapper>

3.编写SqlMapConfig.xml文件

<?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>
<!--    加载jdbc.properties配置文件-->
    <properties resource="jdbc.properties"/>

<!--    定义别名-->
    <typeAliases>
        <typeAlias type="com.hao.domain.User" alias="user"/>
    </typeAliases>

    <!--    注册类型处理器-->
    <typeHandlers>
        <typeHandler handler="com.hao.handler.DateTypeHandler"/>
    </typeHandlers>

    <!--    配置数据源环境-->
    <environments default="development"><!-- 表示默认情况下使用id为development的环境-->
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>

    <!--    加载映射文件-->
    <mappers>
        <mapper resource="com/hao/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

4.自定义类型处理器（必须实现BaseTypeHandler类，泛型中的Date就是要转换的Java类型），实现其中的四个方法

public class DateTypeHandler extends BaseTypeHandler<Date> {
    //将java类型转换为数据库需要的类型
    @Override
    public void setNonNullParameter(PreparedStatement preparedStatement, int i, Date date, JdbcType jdbcType) throws SQLException {
        long time = date.getTime();
        preparedStatement.setLong(i,time);
    }
    //将数据库中的类型转化为Java类型
    //String:要转换的字段的名称
    //ResultSet:查询的结果集
    @Override
    public Date getNullableResult(ResultSet resultSet, String s) throws SQLException {
        //获取结果集中需要的数据(long)转换成Date类型
        long aLong = resultSet.getLong(s);
        Date date = new Date(aLong);
        return date;
    }

    @Override
    public Date getNullableResult(ResultSet resultSet, int i) throws SQLException {
        long aLong = resultSet.getLong(i);
        Date date = new Date(aLong);
        return date;
    }

    @Override
    public Date getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
        long aLong = callableStatement.getLong(i);
        Date date = new Date(aLong);
        return date;
    }
}

5.测试

public class MapperTest {

    @Test
    public void test1() throws IOException {
        InputStream stream = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSession sqlSession = new SqlSessionFactoryBuilder().build(stream).openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = new User();
        user.setUsername("ceshi");
        user.setPassword("abc");
        user.setDate(new Date());
        //执行保存
        mapper.save(user);
        sqlSession.commit();
    }
}

6.结果

---

7.从数据库中读取出来
在UserMapper中添加查询sql语句

<?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.hao.mapper.UserMapper">

    <insert id="save" parameterType="user">
        insert into user values(#{id},#{username},#{password},#{date})
    </insert>
    <select id="findById" parameterType="int" resultType="user">
        select * from user where id=#{id}
    </select>
</mapper>

8.测试

public class MapperTest {

    @Test
    public void test1() throws IOException {
        InputStream stream = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSession sqlSession = new SqlSessionFactoryBuilder().build(stream).openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.findById(8);
        System.out.println(user.getBirthday());
    }
}

9.结果