applicationContext.xml内部发生了什么 [英] What is happening inside applicationContext.xml

问题描述

请问有人解释下面的applicationContext.xml文件在做什么?有关更多信息，请参见 http://persistentdesigns.com/wp/jersey- spring-and-jpa/.

Will someone please explain what the following applicationContext.xml file is doing? For greater context, I get it from http://persistentdesigns.com/wp/jersey-spring-and-jpa/.

我的一些问题(并非详尽无遗，因为我确实不太了解):

Some of my questions (not exhaustive, since I really don't understand much):

• 对于id="dataSource"，dataSource是关键字还是我要使用的数据源的名称?例如，如果我的数据源名称是实际的learningRestDS，是否可以将dataSource替换为learningRestDS?

• For id="dataSource" is dataSource a keyword or is it the name of the datasource I am to use? For example, if the name of my datasource is actuall learningRestDS, do I replace dataSource with learningRestDS?

为什么数据源类名是org.springframework.jdbc.datasource.DriverManagerDataSource而不是com.mysql.jdbc.jdbc2.optional.MysqlDataSource?

Why is the datasource class name org.springframework.jdbc.datasource.DriverManagerDataSource instead of com.mysql.jdbc.jdbc2.optional.MysqlDataSource?

applicationConext.xml:

applicationConext.xml:

<?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:p="http://www.springframework.org/schema/p"
xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context"
xmlns:jee="http://www.springframework.org/schema/jee" xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation="
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.5.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-2.5.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">
   <!--  Scan for both Jersey Rest Annotations a -->
   <context:component-scan base-package="com.persistent.rest,com.persistent.service,com.persistent.service.jpa"/>
   <context:annotation-config />
   <tx:annotation-driven />
   <bean id="dataSource"
    class="org.springframework.jdbc.datasource.DriverManagerDataSource"
    p:driverClassName="com.mysql.jdbc.Driver" p:url="jdbc:mysql://localhost:3306/jpa"
    p:username="user" p:password="password" />

<bean id="entityManagerFactory"
    class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
    p:dataSource-ref="dataSource" p:jpaVendorAdapter-ref="jpaAdapter">
    <property name="loadTimeWeaver">
        <bean
            class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver" />
    </property>
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"
    p:entityManagerFactory-ref="entityManagerFactory" />
<bean id="jpaAdapter"
    class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"
    p:database="MYSQL" p:showSql="true" />

更新:错误:

SEVERE: Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'personService':
Injection of persistence methods failed;
nested exception is org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name 'entityManagerFactory' defined in class path resource [applicationContext.xml]:
Invocation of init method failed; nested exception is java.lang.AbstractMethodError: 
org.springframework.orm.jpa.persistenceunit.SpringPersistenceUnitInfo.getValidationMode()Ljavax/persistence/ValidationMode;

推荐答案

"dataSource"是一个任意的Bean名称(ID)，稍后您将使用该名称来引用该Bean:

"dataSource" is an arbitrary bean name (ID) you use later to reference that bean:

p:dataSource-ref="dataSource"

如果您的数据源名为"learningRestDS"，则应使用:

If your data source was named "learningRestDS" you would use:

p:dataSource-ref="learningRestDS"

p:dataSource-ref是DriverManagerDataSource属性的名称(您将在该类上找到用于注入learningRestDS的setDataSource()方法.

The p:dataSource-ref is the name of the property of DriverManagerDataSource (you'll find setDataSource() method on that class that will be used to inject learningRestDS.

在定义数据源时，您可以自由使用任何实现DataSource接口(抽象的力量)的类.该XML的作者选择使用 DriverManagerDataSource 而不是MysqlDataSource.只要它们都遵守DataSource合同，它们的表现就一样好 ¹ .

When defining a data source you are free to use any class that implements DataSource interface (the power of abstraction). The author of this XML chose to use DriverManagerDataSource instead of MysqlDataSource. They will work just as good¹ as long as they both follow the DataSource contract.

DataSource还有许多其他可能的实现，例如 dbcp 和 c3p0 连接池.它们的优点是它们可以与所有JDBC驱动程序/数据库一起使用.

There are many other possible implementations of DataSource, e.g. dbcp and c3p0 connection pooling libraries. The advantage of them is that they work with all JDBC drivers/databases.

¹ 实际上DriverManagerDataSource仅应用于测试，因为它的性能非常差，但从功能的角度来看，它与任何其他DataSource一样好.

¹ actually DriverManagerDataSource should only be used for testing as it performs very poorly, but from functional perspective, it's as good as any other DataSource.

更新以回答您的评论.您正在看到:

UPDATE to answer your comments. You are seeing:

Invalid property 'driverClassName' of bean class [com.mysql.jdbc.jdbc2.optional.MysqlDataSource]: No property 'driverClassName' found 

这意味着Spring尝试向driverClassName中注入一些东西="nofollow"> MysqlDataSource -不具有此属性(设置程序).这也意味着您引用的应用程序上下文XML文件是不完整/不一致/不正确的，因为您使用的是DriverManagerDataSource.确保这是Spring使用的文件，如果使用MySQL数据源，则删除driverClassName属性.

which means Spring tries to inject something to property driverClassName of MysqlDataSource - which doesn't have such property (setter). This also means that the application context XML file you are quoting is incomplete/inconsistent/incorrect as according to you it uses DriverManagerDataSource. Make sure this is the file Spring uses and remove driverClassName property if MySQL data source is used.

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