Spring 事務管理高階應用難點剖析: 第 3 部分

				
package user.connleak; 
import org.apache.commons.dbcp.BasicDataSource; 
import org.springframework.beans.factory.annotation.Autowired; 
import org.springframework.context.ApplicationContext; 
import org.springframework.context.support.ClassPathXmlApplicationContext; 
import org.springframework.jdbc.core.JdbcTemplate; 
import org.springframework.stereotype.Service; 
import java.sql.Connection; 

@Service("jdbcUserService") 
public class JdbcUserService { 
    @Autowired 
    private JdbcTemplate jdbcTemplate; 

    public void logon(String userName) { 
        try { 
            // ①直接從資料來源獲取連線，後續程式沒有顯式釋放該連線
            Connection conn = jdbcTemplate.getDataSource().getConnection(); 
            String sql = "UPDATE t_user SET last_logon_time=? WHERE user_name =?"; 
            jdbcTemplate.update(sql, System.currentTimeMillis(), userName); 
            Thread.sleep(1000);// ②模擬程式程式碼的執行時間
        } catch (Exception e) { 
            e.printStackTrace(); 
        } 
    } 
} 

				
…
@Service("jdbcUserService")
public class JdbcUserService {
    …
    //①以非同步執行緒的方式執行JdbcUserService#logon()方法，以模擬多執行緒的環境
    public static void asynchrLogon(JdbcUserService userService, String userName) {
        UserServiceRunner runner = new UserServiceRunner(userService, userName);
        runner.start();
    }
    private static class UserServiceRunner extends Thread {
        private JdbcUserService userService;
        private String userName;
        public UserServiceRunner(JdbcUserService userService, String userName) {
            this.userService = userService;
            this.userName = userName;
        }
        public void run() {
            userService.logon(userName);
        }
    }

    //② 讓主執行執行緒睡眠一段指定的時間
    public static void sleep(long time) {
        try {
            Thread.sleep(time);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    
	//③ 彙報資料來源的連線佔用情況
    public static void reportConn(BasicDataSource basicDataSource) {
        System.out.println("連線數[active:idle]-[" +
            basicDataSource.getNumActive()+":"+basicDataSource.getNumIdle()+"]");
    }

    public static void main(String[] args) {
        ApplicationContext ctx = 
            new ClassPathXmlApplicationContext("user/connleak/applicatonContext.xml");
        JdbcUserService userService = (JdbcUserService) ctx.getBean("jdbcUserService");

        BasicDataSource basicDataSource = (BasicDataSource) ctx.getBean("dataSource");
        
		//④彙報資料來源初始連線佔用情況
        JdbcUserService.reportConn(basicDataSource);

        JdbcUserService.asynchrLogon(userService, "tom");
        JdbcUserService.sleep(500);

        //⑤此時執行緒A正在執行JdbcUserService#logon()方法
        JdbcUserService.reportConn(basicDataSource); 

        JdbcUserService.sleep(2000);
        //⑥此時執行緒A所執行的JdbcUserService#logon()方法已經執行完畢
        JdbcUserService.reportConn(basicDataSource);

        JdbcUserService.asynchrLogon(userService, "john");
        JdbcUserService.sleep(500);
        
		//⑦此時執行緒B正在執行JdbcUserService#logon()方法
        JdbcUserService.reportConn(basicDataSource);
        
        JdbcUserService.sleep(2000);
        
		//⑧此時執行緒A和B都已完成JdbcUserService#logon()方法的執行
        JdbcUserService.reportConn(basicDataSource);
    }

				
<?xml version="1.0" encoding="UTF-8" ?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:p="http://www.springframework.org/schema/p"
	xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xsi:schemaLocation="http://www.springframework.org/schema/beans 
	    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context 
		http://www.springframework.org/schema/context/spring-context-3.0.xsd 
		http://www.springframework.org/schema/aop 
		http://www.springframework.org/schema/aop/spring-aop-3.0.xsd 
		http://www.springframework.org/schema/tx 
		http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">
    <context:component-scan base-package="user.connleak"/>
    <bean id="dataSource"
        class="org.apache.commons.dbcp.BasicDataSource"
            destroy-method="close"
            p:driverClassName="oracle.jdbc.driver.OracleDriver"
            p:url="jdbc:oracle:thin:@localhost:1521:orcl"
            p:username="test"
            p:password="test"
            p:defaultAutoCommit="false"/>

    <bean id="jdbcTemplate"
        class="org.springframework.jdbc.core.JdbcTemplate"
        p:dataSource-ref="dataSource"/>

    <bean id="jdbcManager"
        class="org.springframework.jdbc.datasource.DataSourceTransactionManager"
        p:dataSource-ref="dataSource"/>

    <!-- 對JdbcUserService的所有方法實施事務增強 -->
    <aop:config proxy-target-class="true">
        <aop:pointcut id="serviceJdbcMethod"
            expression="within(user.connleak.JdbcUserService+)"/>
        <aop:advisor pointcut-ref="serviceJdbcMethod" 
		    advice-ref="jdbcAdvice" order="0"/>
    </aop:config>
    <tx:advice id="jdbcAdvice" transaction-manager="jdbcManager">
        <tx:attributes>
            <tx:method name="*"/>
        </tx:attributes>
    </tx:advice>
</beans>

				
連線數 [active:idle]-[0:0] 
連線數 [active:idle]-[2:0] 
連線數 [active:idle]-[1:1] 
連線數 [active:idle]-[3:0] 
連線數 [active:idle]-[2:1] 

				
public abstract class DataSourceUtils {
    …
    public static Connection doGetConnection(DataSource dataSource) throws SQLException {
        
		Assert.notNull(dataSource, "No DataSource specified");

        //①首先嚐試從事務同步管理器中獲取資料連線
        ConnectionHolder conHolder = 
            (ConnectionHolder) TransactionSynchronizationManager.getResource(dataSource);
        if (conHolder != null && (conHolder.hasConnection() || 
            conHolder.isSynchronizedWithTransaction())) { 
            conHolder.requested();
            if (!conHolder.hasConnection()) {
                logger.debug(
                    "Fetching resumed JDBC Connection from DataSource");
                conHolder.setConnection(dataSource.getConnection());
            }
			return conHolder.getConnection();
		}
        
		//②如果獲取不到，則直接從資料來源中獲取連線
        Connection con = dataSource.getConnection();

        //③如果擁有事務上下文，則將連線繫結到事務上下文中
        if (TransactionSynchronizationManager.isSynchronizationActive()) {
            ConnectionHolder holderToUse = conHolder;
            if (holderToUse == null) {
				holderToUse = new ConnectionHolder(con);
			}
			else {holderToUse.setConnection(con);}
            holderToUse.requested();
			TransactionSynchronizationManager.registerSynchronization(
                new ConnectionSynchronization(holderToUse, dataSource));
			holderToUse.setSynchronizedWithTransaction(true);
			if (holderToUse != conHolder) {
				TransactionSynchronizationManager.bindResource(
                dataSource, holderToUse);
			}
		}
		return con;
	}
    …
}

				
public void logon(String userName) {
    try {
        //Connection conn = jdbcTemplate.getDataSource().getConnection();
        //①使用DataSourceUtils獲取資料連線
        Connection conn = DataSourceUtils.getConnection(jdbcTemplate.getDataSource());
        String sql = "UPDATE t_user SET last_logon_time=? WHERE user_name =?";
        jdbcTemplate.update(sql, System.currentTimeMillis(), userName);
        Thread.sleep(1000); 
    } catch (Exception e) {
        e.printStackTrace();
    }
}

				
連線數 [active:idle]-[0:0] 
連線數 [active:idle]-[1:0] 
連線數 [active:idle]-[0:1] 
連線數 [active:idle]-[1:0] 
連線數 [active:idle]-[0:1] 

				
連線數 [active:idle]-[0:0] 
連線數 [active:idle]-[1:1] 
連線數 [active:idle]-[1:1] 
連線數 [active:idle]-[2:1] 
連線數 [active:idle]-[2:1] 

				
public void logon(String userName) {
    Connection conn = null;
    try {
        conn = DataSourceUtils.getConnection(jdbcTemplate.getDataSource());
        String sql = "UPDATE t_user SET last_logon_time=? WHERE user_name =?";
        jdbcTemplate.update(sql, System.currentTimeMillis(), userName);
        Thread.sleep(1000);
        // ①
    } catch (Exception e) {
        e.printStackTrace();
    }finally {
        // ②顯式使用DataSourceUtils釋放連線
        DataSourceUtils.releaseConnection(conn,jdbcTemplate.getDataSource());
    }
}

				
public <T> T execute(StatementCallback<T> action) throws DataAccessException {
    //① 首先根據DataSourceUtils獲取資料連線
    Connection con = DataSourceUtils.getConnection(getDataSource());
    Statement stmt = null;
    try {
        Connection conToUse = con;
        …
        handleWarnings(stmt);
        return result;
    }
    catch (SQLException ex) {
        JdbcUtils.closeStatement(stmt);
        stmt = null;
        DataSourceUtils.releaseConnection(con, getDataSource());
        con = null;
        throw getExceptionTranslator().translate(
            "StatementCallback", getSql(action), ex);
    }
    finally {
        JdbcUtils.closeStatement(stmt);
        //② 最後根據DataSourceUtils釋放資料連線
        DataSourceUtils.releaseConnection(con, getDataSource());
    }
}

				
<bean id="dataSource"
    class="org.apache.commons.dbcp.BasicDataSource"
    destroy-method="close"
    p:driverClassName="oracle.jdbc.driver.OracleDriver"
    p:url="jdbc:oracle:thin:@localhost:1521:orcl"
    p:username="test"
    p:password="test"
    p:defaultAutoCommit="false"/>
    
<!-- ①對資料來源進行代理-->
<bean id="dataSourceProxy" 
    class="org.springframework.jdbc.datasource.TransactionAwareDataSourceProxy"
    p:targetDataSource-ref="dataSource"/>
    
<!-- ②直接使用資料來源的代理物件-->
<bean id="jdbcTemplate"
    class="org.springframework.jdbc.core.JdbcTemplate"
    p:dataSource-ref="dataSourceProxy"/>
    
<!-- ③直接使用資料來源的代理物件-->
<bean id="jdbcManager"
    class="org.springframework.jdbc.datasource.DataSourceTransactionManager"
    p:dataSource-ref="dataSourceProxy"/>