Mybatis自定义typeHandle过程解析

一 前言

本篇文章的基础是建立在mybatis配置

二 准备工作

2.1建表语句

CREATE TABLE `customer` (
 `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '主键',
 `customer_name` varchar(255) DEFAULT NULL COMMENT '顾客名称',
 `gender` varchar(255) DEFAULT NULL COMMENT '性别',
 `telephone` varchar(255) DEFAULT NULL COMMENT '电话号码',
 `register_time` timestamp NULL DEFAULT NULL COMMENT '注册时间',
 PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='顾客表';

2.2 实体

public class Customer {
  // 主键
  private Long id;
  // 客户姓名
  private String customer_name;
  // 性别
  private String gender;
  // 电话
  private String telephone;
  // 注册时间
  private Long register_time;
  // 省略 set get
 } 

三 自定义TypeHandler

自定义TypeHandler实现一个业务逻辑就是 当插入数据时可以将时间戳转为timestamp格式；当查询数据得时候再将数据库中得timestamp格式时间转为时间戳；好吧知识追寻者也是无聊透顶了做这种操作，不过易于读者理解；

/**
 * @Author lsc
 * <p> 一个无聊的业务逻辑 输入的是时间戳，到数据库中的是 timestamp 格式 输出的又是时间戳 </p>
 */
@MappedJdbcTypes(JdbcType.TIMESTAMP)
@MappedTypes(Long.class)
public class TimeStringHandler<T> extends BaseTypeHandler<T> {

  public void setNonNullParameter(PreparedStatement preparedStatement, int i, T t, JdbcType jdbcType) throws SQLException {
    // 将 时间戳转为 LocalDateTime
    LocalDateTime localDateTime = LocalDateTime.ofInstant(Instant.ofEpochSecond((java.lang.Long) t), ZoneOffset.ofHours(8));
    // 参数设置
    System.out.println("业务逻辑1");
    preparedStatement.setString(i,localDateTime.toString());
  }

  public T getNullableResult(ResultSet resultSet, String s) throws SQLException {
    System.out.println("业务逻辑2");
    String time = resultSet.getString(s);
    LocalDateTime localDateTime = LocalDateTime.parse(time, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
    Long second = localDateTime.toEpochSecond(ZoneOffset.ofHours(8));
    return (T) second;
  }

  public T getNullableResult(ResultSet resultSet, int i) throws SQLException {
    System.out.println("业务逻辑3");
    String time = resultSet.getString(i);
    LocalDateTime localDateTime = LocalDateTime.parse(time, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
    Long second = localDateTime.toEpochSecond(ZoneOffset.ofHours(8));
    return (T) second;
  }

  public T getNullableResult(CallableStatement callableStatement, int i) throws SQLException {
    System.out.println("业务逻辑4");
    String time = callableStatement.getString(i);
    LocalDateTime localDateTime = LocalDateTime.parse(time, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
    Long second = localDateTime.toEpochSecond(ZoneOffset.ofHours(8));
    return (T) second;
  }
}

四 mappe接口

public interface CustomerMapper {

  // 添加客户
  int addCustomer(Customer customer);
  // 查询客户
  List<Customer> getCustomer();
}

五 sql映射文件

sql映射文件中在使用得字段register_time中做专门得数据类型处理，这样不用配置到全局配置文件中，可以针对特定字段处理是个不错得选择；这边实现得逻辑是两个部分，查询语句用于返回时将register_time使用类型处理器处理；插入语句用于将数据进入数据库时使用register_time使用类型处理器处理。

<?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.zszxz.typehandler.mapper.CustomerMapper">

  <resultMap id="customerMap" type="customer" autoMapping="true">
    <result column="register_time" property="register_time" typeHandler="com.zszxz.typehandler.handler.TimeStringHandler"></result>
  </resultMap>

  <select id="getCustomer" resultMap="customerMap" >
    select * from `customer`
  </select>

  <insert id="addCustomer" parameterType="customer">
     insert into `customer`(
      `customer_name`,
      `gender`,
      `telephone`,
      `register_time`
     )values (
      #{customer_name},
      #{gender},
      #{telephone},
      #{register_time,javaType=Long,jdbcType=TIMESTAMP,typeHandler=com.zszxz.typehandler.handler.TimeStringHandler}
     )
  </insert>
</mapper>

六测试类

测试类 也是分为2部分，查询和新增部分；

/**
 * @Author lsc
 * <p> </p>
 */
@RunWith(JUnit4.class)
public class TypeHandlerTest {

  SqlSession sqlSession = null;

  // @Before 会在执行测试类之前执行该方法
  @Before
  public void before() throws IOException {
    // 资源路径 resource目录下
    String resource = "mybatis-config.xml";
    // 配置mybatis获得输入流
    InputStream inputStream = Resources.getResourceAsStream(resource);
    // 创建 SqlSessionFactory
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    //从 SqlSessionFactory 中获取 SqlSession
    sqlSession= sqlSessionFactory.openSession();
  }

  @Test
  public void testInsert(){
    // 获得mapper的形式
    CustomerMapper mapper = sqlSession.getMapper(CustomerMapper.class);
    Customer customer = new Customer();
    customer.setCustomer_name("知识追寻者");
    customer.setRegister_time(1580739214L);
    customer.setGender("男");
    customer.setTelephone("999");
    // 添加客户
    mapper.addCustomer(customer);
    sqlSession.commit();
    sqlSession.close();
  }

  @Test
  public void testSelect(){
    // 获得mapper的形式
    CustomerMapper mapper = sqlSession.getMapper(CustomerMapper.class);
    List<Customer> customerList = mapper.getCustomer();
    for (Customer customer :customerList){
      System.out.println(customer.getCustomer_name());
      System.out.println(customer.getRegister_time());
    }
    sqlSession.commit();
    sqlSession.close();
  }
}

七 测试插入数据

插入数据时原本register_time是时间戳，从打印得SQL参数2020-02-03T22:13:34(String)可以看见入库时就变成了timestamp支持的格式入库；

[DEBUG] 2020-02-03 23:39:33,018 method:org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:159)
==> Preparing: insert into `customer`( `customer_name`, `gender`, `telephone`, `register_time` )values ( ?, ?, ?, ? )
业务逻辑1
[DEBUG] 2020-02-03 23:39:33,052 method:org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:159)
==> Parameters: 知识追寻者(String), 男(String), 999(String), 2020-02-03T22:13:34(String)
[DEBUG] 2020-02-03 23:39:33,116 method:org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:159)
<== Updates: 1

八 测试查询数据

原本数据库中是timestamp支持的格式得时间，出来就是时间戳；

[DEBUG] 2020-02-03 23:39:00,371 method:org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:159)
==> Preparing: select * from `customer`
[DEBUG] 2020-02-03 23:39:00,410 method:org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:159)
==> Parameters:
业务逻辑2
[DEBUG] 2020-02-03 23:39:00,468 method:org.apache.ibatis.logging.jdbc.BaseJdbcLogger.debug(BaseJdbcLogger.java:159)
<== Total: 1
知识追寻者
1580739214

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