MyBatis拦截器怎么动态替换表名

本篇内容主要讲解"MyBatis拦截器怎么动态替换表名"，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习"MyBatis拦截器怎么动态替换表名"吧!

一、Mybatis Interceptor 拦截器接口和注解

简单的说就是mybatis在执行sql的时候，拦截目标方法并且在前后加上我们的业务逻辑。实际上就是加@Intercepts注解和实现org.apache.ibatis.plugin.Interceptor接口

@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);}

二、实现思路

• 在intercept方法中有参数Invocation对象，里面有3个成员变量和@Signature对应

• 通过Invocation中的args变量。我们能拿到MappedStatement这个对象（args[0]），传入sql语句的参数Object(args[1])。而MappedStatement是一个记录了sql语句（sqlSource对象）、参数值结构、返回值结构、mapper配置等的一个对象。

• sqlSource对象和传入sql语句的参数对象Object就能获得BoundSql。BoundSql的toString方法就能获取到有占位符的sql语句了，我们的业务逻辑就能在这里介入。

• 获取到sql语句，根据规则替换表名，塞回BoundSql对象中、再把BoundSql对象塞回MappedStatement对象中。最后再赋值给args[0]（实际被拦截方法所需的参数）就搞定了

三、代码实现

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 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 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;        }    }}

四、运行结果

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