Mybatis 分表處理

      項目到后期遇到分表查詢處理，但是項目已經快要開發完了而且使用通用mapper不想在改，想了一個辦法在mybatis與mysql數據庫連接時處理sql語句 替換相關表。

第一步，springboot采用注解開發，添加相關配置監聽mybatis.

import org.apache.ibatis.session.SqlSessionFactory;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
 
@Configuration
public class MybatisInterceptorConfig {
    @Bean
    public String myInterceptor(SqlSessionFactory sqlSessionFactory) {
        sqlSessionFactory.getConfiguration().addInterceptor(new MybatisSqlInterceptor());
        return "interceptor";
    }
}

第二步，mybatis在執行sql語句前處理代碼

/***
 * mybatis 執行前 sql處理
 *
 */

import java.sql.SQLException;
import java.util.List;
import java.util.Map;
import java.util.Properties;

import javax.annotation.PostConstruct;

import org.apache.commons.lang3.StringUtils;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.mapping.SqlSource;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.DefaultReflectorFactory;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.factory.DefaultObjectFactory;
import org.apache.ibatis.reflection.wrapper.DefaultObjectWrapperFactory;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;


@Intercepts({
        @Signature(type=Executor.class,method="update",args={MappedStatement.class,Object.class}),
        @Signature(type = Executor.class, method = "query",
                args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})
})
@Component
public class MybatisSqlInterceptor implements Interceptor {
    @Autowired
    private RedisService redisServic2;
    private static RedisService redisService;
    @PostConstruct
    public void beforeInit() {
        //需要注入的類
        redisService=redisServic2;
    }
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        // 獲取sql
        String sql = getSqlByInvocation(invocation);
        if (StringUtils.isBlank(sql)) {
            return invocation.proceed();
        }
        // sql交由處理類處理  對sql語句進行處理  此處是范例  不做任何處理
        String sql2Reset = sql;

        // 包裝sql后，重置到invocation中
        resetSql2Invocation(invocation, sql2Reset);

        // 返回，繼續執行
        return invocation.proceed();
    }
 
    @Override
    public Object plugin(Object obj) {
        return Plugin.wrap(obj, this);
    }
 
    @Override
    public void setProperties(Properties arg0) {
        // doSomething
    }
 
    /**
     * 獲取sql語句
     * @param invocation
     * @return
     */
    private String getSqlByInvocation(Invocation invocation) {
        final Object[] args = invocation.getArgs();
        MappedStatement ms = (MappedStatement) args[0];
        Object parameterObject = args[1];
        BoundSql boundSql = ms.getBoundSql(parameterObject);
        return boundSql.getSql();
    }
 
    /**
     * 包裝sql后，重置到invocation中
     * @param invocation
     * @param sql
     * @throws SQLException
     */
    private void resetSql2Invocation(Invocation invocation, String sql) throws SQLException {
        final Object[] args = invocation.getArgs();
        MappedStatement statement = (MappedStatement) args[0];
        Object parameterObject = args[1];
        BoundSql boundSql = statement.getBoundSql(parameterObject);
        MappedStatement newStatement = newMappedStatement(statement, new BoundSqlSqlSource(boundSql));
        MetaObject msObject =  MetaObject.forObject(newStatement, new DefaultObjectFactory(), new DefaultObjectWrapperFactory(),new DefaultReflectorFactory());
        //========================================================分表處理關鍵位置 start===============================================================
	      //根據需求 替換表
		String tabName="";//表名
		   int tabNameLength=0;//查詢表的長度
		    String suffix="";//后綴
		    tabNameLength=tabName.length();
		    if(sql.indexOf(tabName)!=-1){
                       if(sql.length()>(sql.indexOf(tabName)+tabNameLength+1)){
                           if(sql.substring((sql.indexOf(tabName)+tabNameLength),(sql.indexOf(tabName)+tabNameLength+1)).indexOf("_")==-1){
                               sf=new StringBuffer(sql);
                               sf.replace(sql.indexOf(tabName), sql.indexOf(tabName)+tabNameLength,tabName+suffix);
                               sql=sf.toString();
                           }else if(sql.indexOf(tabName+" ")!=-1){
                               sf=new StringBuffer(sql);
                               sf.replace(sql.indexOf(tabName+" "), sql.indexOf(tabName+" ")+tabNameLength,tabName+suffix);
                               sql=sf.toString();
                           }
                       }else{
                           sql=sql.replace(tabName,tabName+suffix);
                       }
                   }
        //========================================================分表處理關鍵位置 end===============================================================
        msObject.setValue("sqlSource.boundSql.sql", sql);
        args[0] = newStatement;
    }


    private MappedStatement newMappedStatement(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) {
            StringBuilder keyProperties = new StringBuilder();
            for (String keyProperty : ms.getKeyProperties()) {
                keyProperties.append(keyProperty).append(",");
            }
            keyProperties.delete(keyProperties.length() - 1, keyProperties.length());
            builder.keyProperty(keyProperties.toString());
        }
        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();
    }
 
    private String getOperateType(Invocation invocation) {
        final Object[] args = invocation.getArgs();
        MappedStatement ms = (MappedStatement) args[0];
        SqlCommandType commondType = ms.getSqlCommandType();
        if (commondType.compareTo(SqlCommandType.SELECT) == 0) {
            return "select";
        }
        if (commondType.compareTo(SqlCommandType.INSERT) == 0) {
            return "insert";
        }
        if (commondType.compareTo(SqlCommandType.UPDATE) == 0) {
            return "update";
        }
        if (commondType.compareTo(SqlCommandType.DELETE) == 0) {
            return "delete";
        }
        return null;
    }
//    定義一個內部輔助類，作用是包裝sq
    class BoundSqlSqlSource implements SqlSource {
        private BoundSql boundSql;
        public BoundSqlSqlSource(BoundSql boundSql) {
            this.boundSql = boundSql;
        }
        @Override
        public BoundSql getBoundSql(Object parameterObject) {
            return boundSql;
        }
    }
}

　　

以上為 監聽 mybatis與sql連接時處理sql的相關處理代碼，具體需要根據具體需求自行修改相關邏輯。

主要位置：

        //========================================================分表處理關鍵位置 start===============================================================
	      //根據需求 替換表
		String tabName="";//表名
		   int tabNameLength=0;//查詢表的長度
		    String suffix="";//后綴
		    tabNameLength=tabName.length();
		    if(sql.indexOf(tabName)!=-1){
                       if(sql.length()>(sql.indexOf(tabName)+tabNameLength+1)){
                           if(sql.substring((sql.indexOf(tabName)+tabNameLength),(sql.indexOf(tabName)+tabNameLength+1)).indexOf("_")==-1){
                               sf=new StringBuffer(sql);
                               sf.replace(sql.indexOf(tabName), sql.indexOf(tabName)+tabNameLength,tabName+suffix);
                               sql=sf.toString();
                           }else if(sql.indexOf(tabName+" ")!=-1){
                               sf=new StringBuffer(sql);
                               sf.replace(sql.indexOf(tabName+" "), sql.indexOf(tabName+" ")+tabNameLength,tabName+suffix);
                               sql=sf.toString();
                           }
                       }else{
                           sql=sql.replace(tabName,tabName+suffix);
                       }
                   }
        //========================================================分表處理關鍵位置 end===============================================================