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@[toc] In the process of developing mybatis, we often encounter such problems: for example, the date in the mysql table is a string, but we want to operate according to the Date type in java. Therefore, we need to use the typeHandler in mybatis. This article is a field createDate stored in the String type in the database, and its format is "yyyy-MM-ddHH:mm:ss", which is converted to a Date operation by TypeHandler.
1.TypeHandler
Custom TypeHandler needs to inherit BaseTypeHandler. code show as below:
import com.google.common.base.Strings;
import org.apache.ibatis.type.BaseTypeHandler;
import org.apache.ibatis.type.JdbcType;
import org.apache.ibatis.type.MappedJdbcTypes;
import org.apache.ibatis.type.MappedTypes;
import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.Date;
@MappedJdbcTypes(JdbcType.VARCHAR)
@MappedTypes(Date.class)
public class MyDateTypeHandler extends BaseTypeHandler<Date> {
private SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS");
private Date convert(String source) {
Date result = new Date(0);
try {
if (!Strings.isNullOrEmpty(source)) {
result = dateFormat.parse(source);
}
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
@Override
public void setNonNullParameter(PreparedStatement ps, int i, Date parameter, JdbcType jdbcType) throws SQLException {
String result = dateFormat.format(parameter);
ps.setString(i, result);
}
@Override
public Date getNullableResult(ResultSet rs, String columnName) throws SQLException {
String source = rs.getString(columnName);
return convert(source);
}
@Override
public Date getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
String source = rs.getString(columnIndex);
return convert(source);
}
@Override
public Date getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
String source = cs.getString(columnIndex);
return convert(source);
}
}
复制代码In this class, you first need to define the data type in the database through the annotation, @MappedJdbcTypes(JdbcType.VARCHAR). @MappedTypes(Date.class) defines the data types in java objects.
MyDateTypeHandler inherits BaseTypeHandler and needs to implement four methods, one of which is the setNonNullParameter method for converting Date to String, and the other three are methods for converting String in the ResultSet of the database operation result to String. In this example, if the string is empty, an object will be created that defaults to Date(0).
2.generatorConfig.xml
Since the generators will be used to generate the ORM code in reverse, it is necessary to add the columnOverride tag to the table definition to configure the Handler, so that the required code will be created during reverse engineering.
<table tableName="users" domainObjectName="Users">
<columnOverride column="createDate" jdbcType="VARCHAR" javaType="java.util.Date" typeHandler="com.dhb.gts.javacourse.week5.typehandler.MyDateTypeHandler"/>
</table>
复制代码3. Code Generation
The required code can be generated by grale->other->MybatisGenerate.
You can see that in the code entity generated at this time, the type of users' createDate is Date.
主要的操作是在UsersMapper中进行了修改，@insert和select方法的@Results中都添加了MyDateTypeHandler的处理。
package com.dhb.gts.javacourse.week5.mapper;
import com.dhb.gts.javacourse.week5.entity.Users;
import com.dhb.gts.javacourse.week5.entity.UsersExample;
import com.dhb.gts.javacourse.week5.typehandler.MyDateTypeHandler;
import java.util.List;
import org.apache.ibatis.annotations.DeleteProvider;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.InsertProvider;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.SelectProvider;
import org.apache.ibatis.annotations.UpdateProvider;
import org.apache.ibatis.type.JdbcType;
public interface UsersMapper {
@SelectProvider(type=UsersSqlProvider.class, method="countByExample")
long countByExample(UsersExample example);
@DeleteProvider(type=UsersSqlProvider.class, method="deleteByExample")
int deleteByExample(UsersExample example);
@Insert({
"insert into users (id, username, ",
"`password`, createDate)",
"values (#{id,jdbcType=INTEGER}, #{username,jdbcType=VARCHAR}, ",
"#{password,jdbcType=VARCHAR}, #{createdate,jdbcType=VARCHAR,typeHandler=com.dhb.gts.javacourse.week5.typehandler.MyDateTypeHandler})"
})
int insert(Users record);
@InsertProvider(type=UsersSqlProvider.class, method="insertSelective")
int insertSelective(Users record);
@SelectProvider(type=UsersSqlProvider.class, method="selectByExample")
@Results({
@Result(column="id", property="id", jdbcType=JdbcType.INTEGER),
@Result(column="username", property="username", jdbcType=JdbcType.VARCHAR),
@Result(column="password", property="password", jdbcType=JdbcType.VARCHAR),
@Result(column="createDate", property="createdate", typeHandler=MyDateTypeHandler.class, jdbcType=JdbcType.VARCHAR)
})
List<Users> selectByExample(UsersExample example);
@UpdateProvider(type=UsersSqlProvider.class, method="updateByExampleSelective")
int updateByExampleSelective(@Param("record") Users record, @Param("example") UsersExample example);
@UpdateProvider(type=UsersSqlProvider.class, method="updateByExample")
int updateByExample(@Param("record") Users record, @Param("example") UsersExample example);
}
复制代码4.Starter
在springboot中，通过Startler启动，分别插入数据和select进行测试。 启动器：
package com.dhb.gts.javacourse.week5.generator;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@MapperScan(basePackages = {"com.dhb.gts.javacourse.week5.mapper,com.dhb.gts.javacourse.week5.entity"})
public class GeneratorStarter {
public static void main(String[] args) {
SpringApplication.run(GeneratorStarter.class, args);
}
}
复制代码rest的controller:
package com.dhb.gts.javacourse.week5.generator;
import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.serializer.SerializerFeature;
import com.dhb.gts.javacourse.week5.entity.Users;
import com.dhb.gts.javacourse.week5.entity.UsersExample;
import com.dhb.gts.javacourse.week5.mapper.UsersMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Date;
import java.util.List;
import java.util.Random;
@RestController
public class GeneratorController {
@Autowired
private UsersMapper usersMapper;
private Random random = new Random();
@RequestMapping("/generatorquery")
@ResponseBody
public String generatorQuery(HttpServletRequest request, HttpServletResponse response) {
UsersExample example = new UsersExample();
example.createCriteria();
List<Users> list = usersMapper.selectByExample(example);
return JSON.toJSONString(list, SerializerFeature.PrettyFormat, SerializerFeature.WriteMapNullValue,
SerializerFeature.WriteDateUseDateFormat);
}
@RequestMapping("/generatorinsert")
@ResponseBody
public String generatorInsert(HttpServletRequest request, HttpServletResponse response) {
Users users = new Users();
users.setPassword(String.valueOf(System.currentTimeMillis()));
users.setUsername("generatorinsert"+random.nextInt(100));
users.setCreatedate(new Date());
usersMapper.insert(users);
return "success";
}
}
复制代码此外还需注意的是，在springboot的yml文件中要增加如下内容：
# mybatis typehandler
mybatis.type-handlers-package: com.dhb.gts.javacouse.week5.typehandler
复制代码5.运行测试
建表语句如下：
CREATE TABLE users (
id int(11) AUTO_INCREMENT NOT NULL,
username varchar(50) NULL,
password varchar(50) NULL,
createDate varchar(50) NULL,
PRIMARY KEY(id)
)
ENGINE = InnoDB
复制代码通过insert接口http://127.0.0.1:8084/generatorinsert插入数据之后，可以看到数据库中的值：
通过query接口查询如下：
可以看到我们的MyDateTypeHandler对数据进行了转换，在insert和select方法中都起到了作用。