mybatis 中 ObjectWrapperFactory的使用

mybatis 中 ObjectWrapperFactory的使用

ObjectWrapperFactory用于对对象进行包装后处理，在mybatis中用于对结果对象的处理。我们看一下这个接口提供的方法。hasWrapperFor 判断是否满足条件，getWrapperFor 获取ObjectWrapper对象。

public interface ObjectWrapperFactory {

  boolean hasWrapperFor(Object object);

  ObjectWrapper getWrapperFor(MetaObject metaObject, Object object);

}

其实关键的就是使用的ObjectWrapper对对象进行处理，我们看一下mybatis源码是如何匹配上具体的 ObjectWrapperFactory。下面就是获取到具体的ObjectWrapperFactory源码，其实也很简单根据我们在xml中节点配置就可以读取到注入进来了。

  private void objectWrapperFactoryElement(XNode context) throws Exception {
    if (context != null) {
      String type = context.getStringAttribute("type");
      ObjectWrapperFactory factory = (ObjectWrapperFactory) resolveClass(type).newInstance();
      configuration.setObjectWrapperFactory(factory);
    }
  }

在xml中的配置，只需要在mybatis-config.xml中加入标签objectWrapperFactory，下面是我配置的自定义map，key去除下划线的处理。

<objectWrapperFactory type="org.apache.ibatis.dao.mapper.factory.MapWrapperFactory"/>

接下看看如何自定义ObjectWrapperFactory，我们需要实现ObjectWrapperFactory接口，以去除map中key的下划线为例

public class MapWrapperFactory implements ObjectWrapperFactory {
  @Override
  public boolean hasWrapperFor(Object object) {
    return object instanceof Map;
  }

  @Override
  public ObjectWrapper getWrapperFor(MetaObject metaObject, Object object) {
    return new MyMapWrapper(metaObject, (Map<String, Object>)object);
  }
}

在创建MyMapWrapper对象实现ObjectWrapper

package org.apache.ibatis.dao.mapper.wrapper;

import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.wrapper.MapWrapper;

import java.util.Map;

public class MyMapWrapper extends MapWrapper {



  public MyMapWrapper(MetaObject metaObject, Map<String, Object> map) {
    super(metaObject, map);
  }


  @Override
  public String findProperty(String name, boolean useCamelCaseMapping) {
    if (useCamelCaseMapping && ((name.charAt(0) >= 'A' && name.charAt(0) <= 'Z') || name.contains("_"))) {
     return underlineToCamelCase(name);
    }
    return name;
  }
//user_name_log_abc_dd
  private static String underlineToCamelCase(String name) {
    StringBuilder sb = new StringBuilder();
    boolean flag = false;
    for (int i = 0; i < name.length(); i++) {
      if (name.charAt(i) == '_') {
        flag = true;
        continue;
      }else {
        if (flag) {
          sb.append(Character.toUpperCase(name.charAt(i)));
          flag = false;
        }else {
          sb.append(name.charAt(i));
        }
      }
    }
    return sb.toString();
  }

}

接下来我们可以测试一下看看效果，我们先将objectWrapperFactory在xml中去除看看效果，以下是测试代码

    public static void main(String[] args) throws IOException {
        //读取 mybatis-config.xml 文件转成输入流
        Reader resourceAsReader = Resources.getResourceAsReader("org/apache/ibatis/dao/mapper/mybatis-config.xml");

        SqlSessionFactory build = new SqlSessionFactoryBuilder().build(resourceAsReader);
        SqlSession sqlSession = build.openSession();

        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        Map<String, Object> map = mapper.selectById("1723ad77a1ca06b29a011471036a2dd6");
        System.out.println(map);
    }

没有配置objectWrapperFactory的效果,输出的结果可以看到key是带下划线的

{gender=1, last_login_time=2021-03-23 09:55:33.0, create_time=2020-03-22 23:23:12.0, user_name=test1, pass_word=$2a$10$eus6faJ6/X2hNo5Cm.7bK.Z0oP9UQADthoqRaGTwHEdwehnaMj4Lu, role_uid=d105da79260f4d6a8a03571e4a2b17bc, avatar=,70f5b89fe70a28d95e10c19c96bf2e85, uid=1723ad77a1ca06b29a011471036a2dd6, login_count=47, update_time=2021-03-23 09:55:33.0, last_login_ip=0:0:0:0:0:0:0:1, nick_name=test1, email=1595833114@qq.com, status=false}

配置了以后得结果，下划线已经消失了，可以看出objectWrapperFactory配置已经生效了。

{passWord=$2a$10$eus6faJ6/X2hNo5Cm.7bK.Z0oP9UQADthoqRaGTwHEdwehnaMj4Lu, gender=1, nickName=test1, updateTime=2021-03-23 09:55:33.0, avatar=,70f5b89fe70a28d95e10c19c96bf2e85, roleUid=d105da79260f4d6a8a03571e4a2b17bc, userName=test1, loginCount=47, lastLoginIp=0:0:0:0:0:0:0:1, uid=1723ad77a1ca06b29a011471036a2dd6, lastLoginTime=2021-03-23 09:55:33.0, createTime=2020-03-22 23:23:12.0, email=1595833114@qq.com, status=false}