MyBatis拦截器动态替换表名的方法详解

@Intercepts (

         @Signature (method = "query" ,

                 type = Executor. class ,

                 args = {MappedStatement. class , Object. class , RowBounds. class , ResultHandler. class }

         )

)

public interface Interceptor {

   //主要重写这个方法、实现我们的业务逻辑

   Object intercept(Invocation invocation) throws Throwable;

   //生成代理对象，可以在这里判断是否生成代理对象

   Object plugin(Object target);

   //如果我们拦截器需要用到一些变量参数，可以在这里读取

   void setProperties(Properties properties);

}

import org.apache.ibatis.executor.Executor;

import org.apache.ibatis.mapping.BoundSql;

import org.apache.ibatis.mapping.MappedStatement;

import org.apache.ibatis.mapping.SqlSource;

import org.apache.ibatis.plugin.*;

import org.apache.ibatis.session.ResultHandler;

import org.apache.ibatis.session.RowBounds;

import java.util.*;

/**

  * @description: 动态替换表名拦截器

  * @author: hinotoyk

  * @created: 2022/04/19

  */

//method = "query"拦截select方法、而method = "update"则能拦截insert、update、delete的方法

@Intercepts ({

         @Signature (type = Executor. class , method = "query" , args = {MappedStatement. class , Object. class , RowBounds. class , ResultHandler. class }),

         @Signature (type = Executor. class , method = "update" , args = {MappedStatement. class , Object. class })

})

public class ReplaceTableInterceptor implements Interceptor {

     private final static Map<String,String> TABLE_MAP = new LinkedHashMap<>();

     static {

         //表名长的放前面，避免字符串匹配的时候先匹配替换子集

         TABLE_MAP.put( "t_game_partners" , "t_game_partners_test" ); //测试

         TABLE_MAP.put( "t_file_recycle" , "t_file_recycle_other" );

         TABLE_MAP.put( "t_folder" , "t_folder_other" );

         TABLE_MAP.put( "t_file" , "t_file_other" );

     }

     @Override

     public Object intercept(Invocation invocation) throws Throwable {

         Object[] args = invocation.getArgs();

         //获取MappedStatement对象

         MappedStatement ms = (MappedStatement) args[ 0 ];

         //获取传入sql语句的参数对象

         Object parameterObject = args[ 1 ];

         BoundSql boundSql = ms.getBoundSql(parameterObject);

         //获取到拥有占位符的sql语句

         String sql = boundSql.getSql();

         System.out.println( "拦截前sql :" + sql);

         //判断是否需要替换表名

         if (isReplaceTableName(sql)){

             for (Map.Entry<String, String> entry : TABLE_MAP.entrySet()){

                 sql = sql.replace(entry.getKey(),entry.getValue());

             }

             System.out.println( "拦截后sql :" + sql);

             //重新生成一个BoundSql对象

             BoundSql bs = new BoundSql(ms.getConfiguration(),sql,boundSql.getParameterMappings(),parameterObject);

             //重新生成一个MappedStatement对象

             MappedStatement newMs = copyMappedStatement(ms, new BoundSqlSqlSource(bs));

             //赋回给实际执行方法所需的参数中

             args[ 0 ] = newMs;

         }

         return invocation.proceed();

     }

     @Override

     public Object plugin(Object target) {

         return Plugin.wrap(target, this );

     }

     @Override

     public void setProperties(Properties properties) {

     }

     /***

      * 判断是否需要替换表名

      * @param sql

      * @return

      */

     private boolean isReplaceTableName(String sql){

         for (String tableName : TABLE_MAP.keySet()){

             if (sql.contains(tableName)){

                 return true ;

             }

         }

         return false ;

     }

     /***

      * 复制一个新的MappedStatement

      * @param ms

      * @param newSqlSource

      * @return

      */

     private MappedStatement copyMappedStatement (MappedStatement ms, SqlSource newSqlSource) {

         MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId(), newSqlSource, ms.getSqlCommandType());

         builder.resource(ms.getResource());

         builder.fetchSize(ms.getFetchSize());

         builder.statementType(ms.getStatementType());

         builder.keyGenerator(ms.getKeyGenerator());

         if (ms.getKeyProperties() != null && ms.getKeyProperties().length > 0 ) {

             builder.keyProperty(String.join( "," ,ms.getKeyProperties()));

         }

         builder.timeout(ms.getTimeout());

         builder.parameterMap(ms.getParameterMap());

         builder.resultMaps(ms.getResultMaps());

         builder.resultSetType(ms.getResultSetType());

         builder.cache(ms.getCache());

         builder.flushCacheRequired(ms.isFlushCacheRequired());

         builder.useCache(ms.isUseCache());

         return builder.build();

     }

     /***

      * MappedStatement构造器接受的是SqlSource

      * 实现SqlSource接口，将BoundSql封装进去

      */

     public static class BoundSqlSqlSource implements SqlSource {

         private BoundSql boundSql;

         public BoundSqlSqlSource(BoundSql boundSql) {

             this .boundSql = boundSql;

         }

         @Override

         public BoundSql getBoundSql(Object parameterObject) {

             return boundSql;

         }

     }

}