How to use filters in jfinal to monitor Druid for SQL execution?

This article is shared from Huawei cloud community 《

jfinal Filter monitoring in Druid Of SQL perform 【 May 07】

》, author ：KevinQ .

What I want to do at first is to intercept through interceptors SQL perform , For example, similar to PageHelper This plug-in , Through interceptors or filters , Manually modify SQL sentence , To meet certain business requirements , For example, perform paging , Or restrict access to data permissions . But I found the information that the filter is not for this , This is what the database middleware does , such as MyCat etc. .

But it was tested and found that , The filter can listen to at least every SQL Execution and return results of . therefore , Record this exploration .

Configure filters

stay jfinal In the startup configuration class of , There is a function configPlugin(Plugins me) Function to configure the plug-in , This function will be in jfinal Call at startup , The argument to this function is Plugins me, This parameter is a plug-in manager , You can add plug-ins through this plug-in manager .

Database plug-ins Druid Is added in this function .

public void configPlugin(Plugins me) {
 DruidPlugin druidPlugin = createDruidPlugin_holdoa();
 druidPlugin.setPublicKey(p.get("publicKeydebug").trim());
 wallFilter = new WallFilter();
 wallFilter.setDbType("mysql");
 druidPlugin_oa.addFilter(wallFilter);
 druidPlugin_oa.addFilter(new StatFilter());
 me.add(druidPlugin);
}

We refer to WallFilter as well as StatFilter Also create a filter class ：

import com.alibaba.druid.filter.FilterEventAdapter;
public class DataScopeFilter extends FilterEventAdapter {

}

We found that FilterEventAdapter There are several methods in ：

public boolean statement_execute(FilterChain chain, StatementProxy statement, String sql) throws SQLException {...}
protected void statementExecuteUpdateBefore(StatementProxy statement, String sql) {...}
protected void statementExecuteUpdateAfter(StatementProxy statement, String sql, int updateCount) {...}
protected void statementExecuteQueryBefore(StatementProxy statement, String sql) {...}
protected void statementExecuteQueryAfter(StatementProxy statement, String sql, ResultSetProxy resultSet) {...}
protected void statementExecuteBefore(StatementProxy statement, String sql) {...}
protected void statementExecuteAfter(StatementProxy statement, String sql, boolean result) {...}

Let's repeat these methods to see （ exclude Update Method , Because we are more concerned with query statements ）

package xxxx.xxxx;

import com.alibaba.druid.filter.FilterChain;
import com.alibaba.druid.filter.FilterEventAdapter;
import com.alibaba.druid.proxy.jdbc.ResultSetProxy;
import com.alibaba.druid.proxy.jdbc.StatementProxy;
import com.jfinal.kit.LogKit;
import java.sql.SQLException;

public class DataScopeFilter extends FilterEventAdapter {

 @Override
 public boolean statement_execute(FilterChain chain, StatementProxy statement, String sql) throws SQLException {
 LogKit.info("statement_execute");
 return super.statement_execute(chain, statement, sql);
 }

 @Override
 protected void statementExecuteQueryBefore(StatementProxy statement, String sql) {
 LogKit.info("statementExecuteQueryBefore");
 super.statementExecuteQueryBefore(statement, sql);
 }

 @Override
 protected void statementExecuteQueryAfter(StatementProxy statement, String sql, ResultSetProxy resultSet) {
 LogKit.info("statementExecuteQueryAfter");
 super.statementExecuteQueryAfter(statement, sql, resultSet);
 }

 @Override
 protected void statementExecuteBefore(StatementProxy statement, String sql) {
 LogKit.info("statementExecuteBefore");
 super.statementExecuteBefore(statement, sql);
 }

 @Override
 protected void statementExecuteAfter(StatementProxy statement, String sql, boolean result) {
 LogKit.info("statementExecuteAfter");
 super.statementExecuteAfter(statement, sql, result);
 }

 @Override
 public ResultSetProxy statement_executeQuery(FilterChain chain, StatementProxy statement, String sql)
 throws SQLException {
 LogKit.info("statement_executeQuery");
 return super.statement_executeQuery(chain, statement, sql);
 }
}

And then again config Add a filter to the configuration class ：

druidPlugin.addFilter(new DataScopeFilter());

The execution sequence of the initiation is ：

statement_executeQuery
statementExecuteQueryBefore
statementExecuteQueryAfter

View parent code , It is found that the execution logic is , First, execute statement_executeQuery, And then because the method of the parent is called , The parent method body is ：

@Override
 public ResultSetProxy statement_executeQuery(FilterChain chain, StatementProxy statement, String sql)
 throws SQLException {
 statementExecuteQueryBefore(statement, sql);

 try {
 ResultSetProxy resultSet = super.statement_executeQuery(chain, statement, sql);

 if (resultSet != null) {
 statementExecuteQueryAfter(statement, sql, resultSet);
 resultSetOpenAfter(resultSet);
 }

 return resultSet;
 } catch (SQLException error) {
 statement_executeErrorAfter(statement, sql, error);
 throw error;
 } catch (RuntimeException error) {
 statement_executeErrorAfter(statement, sql, error);
 throw error;
 } catch (Error error) {
 statement_executeErrorAfter(statement, sql, error);
 throw error;
 }
 }

This further triggers statementExecuteQueryBefore Methods and statementExecuteQueryAfter Method .

So we , modify statement_executeQuery Method ：

 @Override
 public ResultSetProxy statement_executeQuery(FilterChain chain, StatementProxy statement, String sql)
 throws SQLException {

 statementExecuteQueryBefore(statement, sql);
 ResultSetProxy result = chain.statement_executeQuery(statement, sql);
 statementExecuteQueryAfter(statement, sql, result);
 return result;
 }

such , Let the output result be ：

statementExecuteQueryBefore
statement_executeQuery
statementExecuteQueryAfter

We can do it in Before perhaps After Method , such as ： Record SQL The actual executor of , Operating time , Request execution SQL The interface of .

sql Be declared final type

Find out what's going on SQL stay Druid The corresponding class in is ：DruidPooledPreparedStatement, Its class structure is ：

public class DruidPooledPreparedStatement extends DruidPooledStatement implements PreparedStatement {

 private final static Log LOG = LogFactory.getLog(DruidPooledPreparedStatement.class);

 private final PreparedStatementHolder holder;
 private final PreparedStatement stmt;
 private final String sql;

 ....
}

This means , Once this class is created ,SQL After setting, it cannot be modified , therefore , We need to change SQL Words , It needs to be in prepared The object is modified to the corresponding execution before it is generated SQL.

In the course of debugging , It is found that the following method needs to be overwritten ：

@Override
 public PreparedStatementProxy connection_prepareStatement(FilterChain chain, ConnectionProxy connection, String sql)
 throws SQLException {
 //  It can be modified SQL Purpose
 sql += " LIMIT 1";
 PreparedStatementProxy statement = super.connection_prepareStatement(chain, connection, sql);

 statementPrepareAfter(statement);

 return statement;
 }

We can add custom here SQL Modify the logic , For example, add data permissions and so on .

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