Mybatis自定义Explain插件

Mybatis自定义Explain插件

场景：

最近有个需求：新建一个表的联合索引，让对表的查询走到这个联合索引上

目的：

每次执行sql查询的时候，都能对每一条sql拦截，通过explain分析其性能。看其Extra属性是否为Using index、其key属性是否为新建的索引。

举例：
根据省份name，查province 。explain分析是否，使用了索引。以及走到了ProName索引上

EXPLAIN select distinct
    ProID
    ,ProName
    from province p
     WHERE p.ProName = ?

实现

自定义impl类实现Interceptor接口

import com.baomidou.mybatisplus.core.exceptions.MybatisPlusException;
import org.apache.ibatis.builder.StaticSqlSource;
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.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.scripting.defaults.DefaultParameterHandler;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;
import org.springframework.stereotype.Component;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;
@Component
@Intercepts({
    
    
        @Signature(
                type = Executor.class,
                method = "query",
                args = {
    
    MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class
                }
        )
})
public class ExplainInterceptor implements Interceptor {
    
    
    @Override
    public Object intercept(Invocation invocation) throws Throwable {
    
    
        MappedStatement ms = (MappedStatement) invocation.getArgs()[0];
        if (ms.getSqlCommandType() == SqlCommandType.SELECT) {
    
    
            Executor executor = (Executor) invocation.getTarget();
            Configuration configuration = ms.getConfiguration();
            Object parameter = invocation.getArgs()[1];
            BoundSql boundSql = ms.getBoundSql(parameter);
            Connection connection = executor.getTransaction().getConnection();
            sqlExplain(configuration, ms, boundSql, connection, parameter);
        }

        Object result = invocation.proceed();//target对象应执行的方法
        return result;
    }

    private void sqlExplain(Configuration configuration, MappedStatement mappedStatement, BoundSql boundSql, Connection connection, Object parameter) {
    
    
        // 这里注意：EXPLAIN后面必须要有空格，否则sql为： explainselect报错
        StringBuilder explain = new StringBuilder("EXPLAIN ");
        String sqlExplain = explain.append(boundSql.getSql()).toString();
        System.out.println("============================================");
        System.out.println(sqlExplain);
        System.out.println("============================================");
        StaticSqlSource sqlSource = new StaticSqlSource(configuration, sqlExplain, boundSql.getParameterMappings());
        MappedStatement.Builder builder = new MappedStatement.Builder(configuration, "explain_sql", sqlSource, SqlCommandType.SELECT);
        MappedStatement queryStatement = builder.build();
        builder.resultMaps(mappedStatement.getResultMaps()).resultSetType(mappedStatement.getResultSetType())
                .statementType(mappedStatement.getStatementType());
        DefaultParameterHandler handler = new DefaultParameterHandler(queryStatement, parameter, boundSql);
        try {
    
    
            PreparedStatement stmt = connection.prepareStatement(sqlExplain);
            handler.setParameters(stmt);
            ResultSet rs = stmt.executeQuery();
            while (rs.next()){
    
    
                String extra = rs.getString("Extra");
                int index = extra.indexOf("Using index");
                //判断，是否走了索引。还是走的Using where
                if (index == -1){
    
    
                    throw new MybatisPlusException("Error:Full table operator is prohibited. SQL:"+boundSql.getSql());
                }
                //判断，是否走到索引idx_ProName上 
                if (!"idx_ProName".equals(rs.getString("key"))){
    
    
                    throw new MybatisPlusException("Error:idx is not used. SQL:"+boundSql.getSql());
                }
            }
        } catch (SQLException e) {
    
    
            e.printStackTrace();
        }

    }

    @Override
    public Object plugin(Object target) {
    
    
        return Plugin.wrap(target, this);
    }

    @Override
    public void setProperties(Properties properties) {
    
    
        Interceptor.super.setProperties(properties);
    }
}