对spring JdbcTemplate的一个扩展(使其支持单Connection)

对spring JdbcTemplate的一个扩展(使其支持单Connection).

不怕大家笑话,以前一直没怎么使用过spring jdbc template,
印象中只用过
public List queryForList(String sql, Object[] args)
public Map queryForMap(String sql, Object[] args)
和SqlFunction

在orm大行其道,spring诞生快一个实际的今天,再来探讨jdbc的一些封装实在不知道有没有意义.
不过还是想把刚刚弄出来的一点东西和大家分享.

看了一下 JdbcTemplate,
发现起核心是那几个 execute 方法.
而那几个execute方法的机构大概是这样(重点讨论Connection,所以其他地方从简)

execute方法开始

  Connection con = DataSourceUtils.getConnection(getDataSource());

  // 做一些数据库操作

  DataSourceUtils.releaseConnection(con, getDataSource());

execute方法结束

当你要批量执行一些操作时(不是 每个操作使用不同的sql,或者是其他不适合 addBatch的情形).

如下:

JdbcTemplate jdbcTemplate=new JdbcTemplate(ds);
jdbcTemplate.query(sql_1, args_1,rch_1);
jdbcTemplate.query(sql_2, args_2,rch_2);
jdbcTemplate.query(sql_3, args_3,rch_3);
jdbcTemplate.query(sql_4, args_4,rch_4);
......

此时,在内部实际上执行了,n次 getConnection,releaseConnection.

而这些操作,在很多时候,是可以通过一个Connection来完成的.

我的扩展就是实现了这个功能.

JdbcTemplatePlus jdbcTemplate=new JdbcTemplatePlus(ds);
// 内部使用一个唯一的Connection
jdbcTemplate.setUseOneConnection(true);
jdbcTemplate.query(sql_1, args_1,rch_1);
jdbcTemplate.query(sql_2, args_2,rch_2);
jdbcTemplate.query(sql_3, args_3,rch_3);
jdbcTemplate.query(sql_4, args_4,rch_4);
......
// 最后调用该方法 释放那个内部唯一的Connection
// 虽然我在finalize 里调用了,不过finalize毕竟不是总能在正确的时间被正确的调用
jdbcTemplate.releaseConnection();

我们系统中,有大量的嵌套查询.使用该JdbcTemplatePlus的唯一Connection特性后,类似的操作速度提升明显.
(不过可能我们原先的做法不对,也许 spring内部已经实现这个机制了 这些我就不明白了,欢迎大家来指正)
我们原先的做法(伪代码):

public List queryNsubQueryUserList(Map param){

	// 外层查询
	final String bsql="select * from ......";
	final JdbcTemplate jdbcTemplate=createJdbcTemplate();
	
	// 子查询相关
	final String subSql="select ............ ";
	final JdbcTemplate subJdbcTemplate=createJdbcTemplate();
	
	List rslist=jdbcTemplate.query(bsql.toString(),sqlArg, 
		new ResultSetHandler(){
			public void processRow(ResultSet rs) throws SQLException {
				final 一个VO recordObj=new 一个VO();
				// 子查询
				subJdbcTemplate.query(subSql, subQueryArgs, 
					new ResultSetHandler(){
						public void processRow(ResultSet rs) throws SQLException {
							// 一些操作........
						}
					}
				);
					// 一些操作........
					recordObj.setXXXXX(rs.getString("XXXXX"));
					.........
					// 将记录放入集合
					addRecord(recordObj);
			}
		}
	);
	return rslist;
	}
}

在使用 JdbcTemplatePlus 代替 JdbcTemplate,并设置.setUseOneConnection(true)后,
耗时变为原先的1/8左右.


扩展的 JdbcTemplatePlus 代码如下,欢迎大家拍砖,挑错.
对 execute方法的修改如下:
把所有的 this.ativeJdbcExtractor换成 getNativeJdbcExtractor(), 这个是必须的 呵呵.

把所有 Connection con = DataSourceUtils.getConnection(getDataSource()); 换成
Connection con = tryGetConnection();

把所有 DataSourceUtils.releaseConnection(con, getDataSource());  换成
tryReleaseConnection(con);

package com.neusoft.tdframework.dao;

import java.sql.CallableStatement;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;

import javax.sql.DataSource;

import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.CallableStatementCallback;
import org.springframework.jdbc.core.CallableStatementCreator;
import org.springframework.jdbc.core.ConnectionCallback;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.ParameterDisposer;
import org.springframework.jdbc.core.PreparedStatementCallback;
import org.springframework.jdbc.core.PreparedStatementCreator;
import org.springframework.jdbc.core.SqlProvider;
import org.springframework.jdbc.core.StatementCallback;
import org.springframework.jdbc.datasource.DataSourceUtils;
import org.springframework.jdbc.support.JdbcUtils;
import org.springframework.util.Assert;

public class JdbcTemplatePlus extends JdbcTemplate {

	private Connection connection=null;
	private boolean useOneConnection=false;


	public JdbcTemplatePlus() {
		super();
	}
	public JdbcTemplatePlus(DataSource dataSource) {
		super(dataSource);
	}
	public JdbcTemplatePlus(DataSource dataSource, boolean lazyInit) {
		super(dataSource,lazyInit);
	}
	
	private Connection tryGetConnection(){
		if (useOneConnection){
			if (connection==null){
				connection= DataSourceUtils.getConnection(getDataSource());
			}
			return connection;
		}
		return DataSourceUtils.getConnection(getDataSource());
	}
	
	private void tryReleaseConnection(Connection con){
		if (!useOneConnection){
			DataSourceUtils.releaseConnection(con, getDataSource());
		}
	}
	
	public Connection getConnection(){
		return connection;
	}
	
	public void setConnection(Connection connection){
		this.connection=connection;
	}
	
	public boolean isUseOneConnection() {
		return useOneConnection;
	}

	public void setUseOneConnection(boolean useOneConnection) {
		this.useOneConnection = useOneConnection;
	}
	
	public void releaseConnection(){
		DataSourceUtils.releaseConnection(connection, getDataSource());
	}
	
	
	// 不明白这个方法为什么spring不把他弄成 protected 或 public,
	// 导致我要重写execute方法时还必须要重写这个方法  :(
	public static String getSql(Object sqlProvider) {
		if (sqlProvider instanceof SqlProvider) {
			return ((SqlProvider) sqlProvider).getSql();
		}
		else {
			return null;
		}
	}
	
	/*
		对 execute方法的修改如下:
		把所有的 this.ativeJdbcExtractor换成 getNativeJdbcExtractor(), 这个是必须的 呵呵.
		
		把所有 Connection con = DataSourceUtils.getConnection(getDataSource()); 换成
		Connection con = tryGetConnection();
		
		把所有 DataSourceUtils.releaseConnection(con, getDataSource());  换成
		tryReleaseConnection(con);
	 */
	
	public Object execute(ConnectionCallback action) throws DataAccessException {
		Assert.notNull(action, "Callback object must not be null");

		Connection con = tryGetConnection();
		try {
			Connection conToUse = con;
			if (getNativeJdbcExtractor() != null) {
				conToUse = getNativeJdbcExtractor().getNativeConnection(con);
			} else {
				conToUse = createConnectionProxy(con);
			}
			return action.doInConnection(conToUse);
		} catch (SQLException ex) {
			tryReleaseConnection(con);
			con = null;
			throw getExceptionTranslator().translate("ConnectionCallback",
					getSql(action), ex);
		} finally {
			tryReleaseConnection(con);
		}
	}

	public Object execute(StatementCallback action) throws DataAccessException {
		Assert.notNull(action, "Callback object must not be null");

		Connection con = tryGetConnection();
		Statement stmt = null;
		try {
			Connection conToUse = con;
			if (getNativeJdbcExtractor() != null
					&& getNativeJdbcExtractor()
							.isNativeConnectionNecessaryForNativeStatements()) {
				conToUse = getNativeJdbcExtractor().getNativeConnection(con);
			}
			stmt = conToUse.createStatement();
			applyStatementSettings(stmt);
			Statement stmtToUse = stmt;
			if (getNativeJdbcExtractor() != null) {
				stmtToUse = getNativeJdbcExtractor().getNativeStatement(stmt);
			}
			Object result = action.doInStatement(stmtToUse);
			handleWarnings(stmt.getWarnings());
			return result;
		} catch (SQLException ex) {
			JdbcUtils.closeStatement(stmt);
			stmt = null;
			tryReleaseConnection(con);
			con = null;
			throw getExceptionTranslator().translate("StatementCallback",
					getSql(action), ex);
		} finally {
			JdbcUtils.closeStatement(stmt);
			tryReleaseConnection(con);
		}
	}

	public Object execute(PreparedStatementCreator psc,
			PreparedStatementCallback action) throws DataAccessException {

		Assert.notNull(psc, "PreparedStatementCreator must not be null");
		Assert.notNull(action, "Callback object must not be null");
		if (logger.isDebugEnabled()) {
			String sql = getSql(psc);
			logger.debug("Executing prepared SQL statement"
					+ (sql != null ? " [" + sql + "]" : ""));
		}

		Connection con = tryGetConnection();
		PreparedStatement ps = null;
		try {
			Connection conToUse = con;
			if (getNativeJdbcExtractor() != null
					&& getNativeJdbcExtractor()
							.isNativeConnectionNecessaryForNativePreparedStatements()) {
				conToUse = getNativeJdbcExtractor().getNativeConnection(con);
			}
			ps = psc.createPreparedStatement(conToUse);
			applyStatementSettings(ps);
			PreparedStatement psToUse = ps;
			if (getNativeJdbcExtractor() != null) {
				psToUse = getNativeJdbcExtractor()
						.getNativePreparedStatement(ps);
			}
			Object result = action.doInPreparedStatement(psToUse);
			handleWarnings(ps.getWarnings());
			return result;
		} catch (SQLException ex) {
			if (psc instanceof ParameterDisposer) {
				((ParameterDisposer) psc).cleanupParameters();
			}
			String sql = getSql(psc);
			psc = null;
			JdbcUtils.closeStatement(ps);
			ps = null;
			tryReleaseConnection(con);
			con = null;
			throw getExceptionTranslator().translate(
					"PreparedStatementCallback", sql, ex);
		} finally {
			if (psc instanceof ParameterDisposer) {
				((ParameterDisposer) psc).cleanupParameters();
			}
			JdbcUtils.closeStatement(ps);
			tryReleaseConnection(con);
		}
	}

	public Object execute(CallableStatementCreator csc,
			CallableStatementCallback action) throws DataAccessException {

		Assert.notNull(csc, "CallableStatementCreator must not be null");
		Assert.notNull(action, "Callback object must not be null");
		if (logger.isDebugEnabled()) {
			String sql = getSql(csc);
			logger.debug("Calling stored procedure"
					+ (sql != null ? " [" + sql + "]" : ""));
		}

		Connection con = tryGetConnection();
		CallableStatement cs = null;
		try {
			Connection conToUse = con;
			if (getNativeJdbcExtractor() != null) {
				conToUse = getNativeJdbcExtractor().getNativeConnection(con);
			}
			cs = csc.createCallableStatement(conToUse);
			applyStatementSettings(cs);
			CallableStatement csToUse = cs;
			if (getNativeJdbcExtractor() != null) {
				csToUse = getNativeJdbcExtractor()
						.getNativeCallableStatement(cs);
			}
			Object result = action.doInCallableStatement(csToUse);
			handleWarnings(cs.getWarnings());
			return result;
		} catch (SQLException ex) {
			// Release Connection early, to avoid potential connection pool
			// deadlock
			// in the case when the exception translator hasn't been initialized
			// yet.
			if (csc instanceof ParameterDisposer) {
				((ParameterDisposer) csc).cleanupParameters();
			}
			String sql = getSql(csc);
			csc = null;
			JdbcUtils.closeStatement(cs);
			cs = null;
			tryReleaseConnection(con);
			con = null;
			throw getExceptionTranslator().translate(
					"CallableStatementCallback", sql, ex);
		} finally {
			if (csc instanceof ParameterDisposer) {
				((ParameterDisposer) csc).cleanupParameters();
			}
			JdbcUtils.closeStatement(cs);
			tryReleaseConnection(con);
		}
	}


	protected void finalize() throws Throwable{
		super.finalize();
		releaseConnection();
	}


	
}