Spring事务管理高级应用难点剖析(2)-文章-软件开发-程序设计

Spring事务管理高级应用难点剖析(2)

时间:04-15 10:45 阅读:1239次

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简介：介绍Spring事务管理高级应用难点剖析(2)

应用分层的迷惑

Web、Service及DAO三层划分就像西方国家的立法、行政、司法三权分立一样被奉为金科玉律,甚至有开发人员认为如果要使用Spring事务管理就一定先要进行三层的划分.这个看似荒唐的论调在开发人员中颇有市场.更有甚者,认为每层先定义一个接口,然后再定义一个实现类.其结果是：一个很简单的功能,也至少需要3个接口,3个类,再加上视图层的JSP和JS等,打牌都可以转上两桌了,这种误解贻害不浅.

对将“面向接口编程”奉为圭臬,认为放之四海而皆准的论调,笔者深不以为然.是的,“面向接口编程”是MartinFowler,RodJohnson这些大师提倡的行事原则.如果拿这条原则去开发架构,开发产品,怎么强调都不为过.但是,对于我们一般的开发人员来说,做的最多的是普通工程项目,往往最多的只是一些对数据库增、删、查、改的功能.此时,“面向接口编程”除了带来更多的类文件外,看不到更多其它的好处.

Spring框架提供的所有附加的好处（AOP、注解增强、注解MVC等）唯一的前提就是让POJO的类变成一个受Spring容器管理的Bean,除此以外没有其它任何的要求.下面的实例用一个POJO完成所有的功能,既是Controller,又是Service,还是DAO：

清单5.MixLayerUserService.java

62.packageuser.mixlayer;

63.importorg.springframework.beans.factory.annotation.Autowired;

64.importorg.springframework.jdbc.core.JdbcTemplate;

65.importorg.springframework.stereotype.Controller;

66.importorg.springframework.web.bind.annotation.RequestMapping;

67.//①.将POJO类通过注解变成SpringMVC的Controller

68.@Controller

69.publicclassMixLayerUserService{

70.

71.//②.自动注入JdbcTemplate

72.@Autowired

73.privateJdbcTemplatejdbcTemplate;

74.

75.//③.通过SpringMVC注解映URL请求

76.@RequestMapping("/logon.do")

77.publicStringlogon(StringuserName,Stringpassword){

78.if(isRightUser(userName,password)){

79.Stringsql="UPDATEt_useruSETu.score=u.score ?WHEREuser_name=?";

80.jdbcTemplate.update(sql,20,userName);

81.return"success";

82.}else{

83.return"fail";

84.}

85.}

86.privatebooleanisRightUser(StringuserName,Stringpassword){

87.//dosth...

88.returntrue;

89.}

90.}

通过@Controller注解将MixLayerUserService变成Web层的Controller,同时也是Service层的服务类.此外,直接使用JdbcTemplate访问数据,MixLayerUserService还是一个DAO.来看一下对应的Spring配置文件：

清单6.applicationContext.xml

91.<?xmlversionxmlversion="1.0"encoding="UTF-8"?>

92.<beansxmlnsbeansxmlns="http://www.springframework.org/schema/beans"

93.xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

94.xmlns:context="http://www.springframework.org/schema/context"

95.xmlns:p="http://www.springframework.org/schema/p"

96.xmlns:aop="http://www.springframework.org/schema/aop"

97.xmlns:tx="http://www.springframework.org/schema/tx"

98.xsi:schemaLocation="http://www.springframework.org/schema/beans

99.http://www.springframework.org/schema/beans/spring-beans-3.0.xsd

100.http://www.springframework.org/schema/context

101. http://www.springframework.org/schema/context/spring-context-3.0.xsd

102. http://www.springframework.org/schema/aop

103. http://www.springframework.org/schema/aop/spring-aop-3.0.xsd

104. http://www.springframework.org/schema/tx

105.http://www.springframework.org/schema/tx/spring-tx-3.0.xsd">

106.

107.<context:component-scanbase-packagecontext:component-scanbase-package="user.mixlayer"/>

108.

109.<beanclassbeanclass="org.springframework.web.servlet.mvc.annotation

110. .AnnotationMethodHandlerAdapter"/>

111.

112.

113.<beanclassbeanclass="org.springframework.web.servlet.view

114. .InternalResourceViewResolver"

115.pp:prefix="/WEB-INF/jsp/"p:suffix=".jsp"/>

116.

117.

118.<beanidbeanid="dataSource"

119.class="org.apache.commons.dbcp.BasicDataSource"

120.destroy-method="close"

121.p:driverClassName="oracle.jdbc.driver.OracleDriver"

122.p:url="jdbc:oracle:thin:@localhost:1521:orcl"

123.p:username="test"

124.p:password="test"/>

125.

126.<beanidbeanid="jdbcTemplate"

127.class="org.springframework.jdbc.core.JdbcTemplate"

128.p:dataSource-ref="dataSource"/>

129.

130.

131.<beanidbeanid="jdbcManager"

132.class="org.springframework.jdbc.datasource.DataSourceTransactionManager"

133.p:dataSource-ref="dataSource"/>

134.

135.

136.<aop:configproxy-target-classaop:configproxy-target-class="true">

137.<aop:pointcutidaop:pointcutid="serviceJdbcMethod"

138.expression="execution(public*user.mixlayer.MixLayerUserService.*(..))"/>

139.<aop:advisorpointcut-refaop:advisorpointcut-ref="serviceJdbcMethod"

140.advice-ref="jdbcAdvice"order="0"/>

141.</aop:config>

142.<tx:adviceidtx:adviceid="jdbcAdvice"transaction-manager="jdbcManager">

143.<tx:attributes>

144.<tx:methodnametx:methodname="*"/>

145.</tx:attributes>

146.</tx:advice>

147.</beans>

在①处,我们定义配置了AnnotationMethodHandlerAdapter,以便启用SpringMVC的注解驱动功能.而②和③处通过Spring的aop及tx命名空间,以及Aspject的切点表达式语法进行事务增强的定义,对MixLayerUserService的所有公有方法进行事务增强.要使程序能够运行起来还进行web.xml的相关配置：

清单7.web.xml

1.<?xmlversionxmlversion="1.0"encoding="GB2312"?>

2.<web-appversionweb-appversion="2.4"xmlns="http://java.sun.com/xml/ns/j2ee"

3.xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

4.xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee

5.http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

6.<context-param>

7.<param-name>contextConfigLocation</param-name>

8.<param-value>classpath*:user/mixlayer/applicationContext.xml</param-value>

9.</context-param>

10.<context-param>

11.<param-name>log4jConfigLocation</param-name>

12.<param-value>/WEB-INF/classes/log4j.properties</param-value>

13.</context-param>

14.

15.<listener>

16.<listener-class>

17.org.springframework.web.util.Log4jConfigListener

18.</listener-class>

19.</listener>

20.<listener>

21.<listener-class>

22.org.springframework.web.context.ContextLoaderListener

23.</listener-class>

24.</listener>

25.

26.<servlet>

27.<servlet-name>user</servlet-name>

28.<servlet-class>

29.org.springframework.web.servlet.DispatcherServlet

30.</servlet-class>

31.

32.<init-param>

33.<param-name>contextConfigLocation</param-name>

34.<param-value>classpath:user/mixlayer/applicationContext.xml</param-value>

35.</init-param>

36.<load-on-startup>1</load-on-startup>

37.</servlet>

38.<servlet-mapping>

39.<servlet-name>user</servlet-name>

40.<url-pattern>*.do</url-pattern>

41.</servlet-mapping>

42.</web-app>

这个配置文件很简单,唯一需要注意的是DispatcherServlet的配置.默认情况下SpringMVC根据Servlet的名字查找WEB-INF下的-servlet.xml作为SpringMVC的配置文件,在此,我们通过contextConfigLocation参数显式指定SpringMVC配置文件的确切位置.

将org.springframework.jdbc及org.springframework.transaction的日志级别设置为DEBUG,启动项目,并访问http://localhost:8088/logon.do?userName=tom应用,MixLayerUserService#logon方法将作出响应,查看后台输出日志：

清单8执行日志

43.13:24:22,625DEBUG(AbstractPlatformTransactionManager.java:365)-

44.Creatingnewtransactionwithname

45. [user.mixlayer.MixLayerUserService.logon]:PROPAGATION_REQUIRED,ISOLATION_DEFAULT

46.13:24:22,906DEBUG(DataSourceTransactionManager.java:205)-

47.AcquiredConnection[org.apache.commons.dbcp.PoolableConnection@6e1cbf]

48. forJDBCtransaction

49.13:24:22,921DEBUG(DataSourceTransactionManager.java:222)-

50.SwitchingJDBCConnection

51. [org.apache.commons.dbcp.PoolableConnection@6e1cbf]tomanualcommit

52.13:24:22,921DEBUG(JdbcTemplate.java:785)-

53.ExecutingpreparedSQLupdate