mybatis拦截器 修改mybatis返回结果集中的字段的值

项目中使用了shardingJDBC，业务库做了分库，公共库没在一起，所以导致做码值转换的时候，需要在实现类里面做转码，重复的代码量大，故考虑用mybatis拦截器，将码值转换后再做返回给实现类。

 

import org.apache.commons.beanutils.BeanUtils;
import org.apache.ibatis.executor.resultset.DefaultResultSetHandler;
import org.apache.ibatis.executor.resultset.ResultSetHandler;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.ResultMap;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import org.apache.ibatis.session.Configuration;

import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Properties;

@Intercepts({ @Signature(type = ResultSetHandler.class, method = "handleResultSets", args = { Statement.class }) })
public class MyPlugin implements Interceptor {
    // //这里是每次执行操作的时候，都会进行这个拦截器的方法内
    public Object intercept(Invocation invocation) throws Throwable {
        List resList = new ArrayList();
        DefaultResultSetHandler defaultResultSetHandler = (DefaultResultSetHandler) invocation.getTarget();
        MetaObject metaStatementHandler = SystemMetaObject.forObject(defaultResultSetHandler);
        MappedStatement mappedStatement = (MappedStatement) metaStatementHandler.getValue("mappedStatement");
        //获取节点属性的集合
        List<ResultMap> resultMaps = mappedStatement.getResultMaps();
        Configuration configuration = (Configuration)metaStatementHandler.getValue("configuration");
        Class<?> resultType = resultMaps.get(0).getType();
        //获取mybatis返回的实体类类型名
        int resultMapCount = resultMaps.size();
        if (resultMapCount > 0) {
            Statement statement = (Statement) invocation.getArgs()[0];
            ResultSet resultSet = statement.getResultSet();
            if (resultSet != null) {
                //获得对应列名
                ResultSetMetaData rsmd = resultSet.getMetaData();
                List<String> columnList = new ArrayList<String>();
                for (int i = 1; i <= rsmd.getColumnCount(); i++) {
                    columnList.add(rsmd.getColumnName(i));
                }
                while (resultSet.next()) {
                    LinkedHashMap<String, Object> resultMap = new LinkedHashMap<String, Object>();
                    for (String colName : columnList) {
                        resultMap.put(colName, resultSet.getString(colName));
                        //具体些要转换的码值这里就做个演示
                        if(colName.equals("username")){
                            resultMap.put(colName, "iui");
                        }
                    }
                    Object o = resultType.newInstance();
                    //将转换后的map转换为实体类中
                    BeanUtils.populate(o,resultMap);
                    resList.add(o);

                }
                return resList;
            }
        }
        return invocation.proceed();
    }

/**
 *   //主要是为了把这个拦截器生成一个代理放到拦截器链中
 *   ^Description包装目标对象 为目标对象创建代理对象
 *   @Param target为要拦截的对象
 *   @Return代理对象
 */
    public Object plugin(Object target) {
        System.out.println("将要包装的目标对象："+target);
        return Plugin.wrap(target,this);
   }

    public void setProperties(Properties properties) {

    }
}

sqlMapperConfig.xml中添加拦截器

<plugins>
    <plugin interceptor="com.lagou.plugin.MyPlugin"></plugin>
</plugins>
 

mybatis查询的的原数据

<==    Columns: id, username, password, birthday
<==        Row: 1, lys, 123, 2019-12-12
<==        Row: 2, tom, 1223, 2019-12-12
<==        Row: 3, zt, 3211645, 1988-02-01
<==        Row: 5, jack, 37652, 1958-05-05
<==        Row: 6, jacket, 37652, 2008-05-05
<==        Row: 7, jack, 37652, 1958-05-05
<==      Total: 6

加入插件后返回的实体类对象

User{id=1, username='iui', password='123', birthday='2019-12-12'}
User{id=2, username='iui', password='1223', birthday='2019-12-12'}
User{id=3, username='iui', password='3211645', birthday='1988-02-01'}
User{id=5, username='iui', password='37652', birthday='1958-05-05'}
User{id=6, username='iui', password='37652', birthday='2008-05-05'}
User{id=7, username='iui', password='37652', birthday='1958-05-05'}

感谢！

https://www.cnblogs.com/SmallHan/articles/8127327.html

http://www.voidcn.com/article/p-qmbnexxp-bos.html