JPA(Toplink) Error : Object: xxxxxx is not a known entity type. 解决

 出错可能的原因如下:

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean" p:dataSource-ref="dataSource" p:persistenceUnitName="jpaToplinkPersistenceUnit"> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.TopLinkJpaVendorAdapter" p:showSql="true" p:generateDdl="true" p:databasePlatform="oracle.toplink.essentials.platform.database.HSQLPlatform" /> </property> <property name="loadTimeWeaver"> <bean class="org.springframework.instrument.classloading.SimpleLoadTimeWeaver"/> </property> </bean>

问题出在：<property name="loadTimeWeaver">上。

更改配置方法：注掉loadTimeWeaver，使用<context:load-time-weaver/>标签即可。

 

注意：tomcat服务器下需要把Spring包下：spring-tomcat-weaver.jar拷贝到Tomcat的lib里，并在/conf/Catalina/localhost下追加形如下面的配置文件：xxxx(工程wen路径).xml

<Context path="/xxxx" reloadable="false"> <Loader loaderClass="org.springframework.instrument.classloading.tomcat.TomcatInstrumentableClassLoader" useSystemClassLoaderAsParent="false"/> </Context>

 

或者参考官方的配置方式：

3. JPA ON TOMCAT Notes on using the Java Persistence API (JPA) on Apache Tomcat 4.x or higher, with a persistence provider that requires class instrumentation (such as TopLink Essentials): To use JPA class instrumentation, Tomcat has to be instructed to use a custom class loader which supports instrumentation. See the JPA section of the Spring reference manual for complete details. The basic steps are: - Copy "spring-tomcat-weaver.jar" from the Spring distribution to "TOMCAT_HOME/server/lib". - If you're running on Tomcat 5.x, modify "TOMCAT_HOME/conf/server.xml" and add a new "<Context>" element for 'petclinic' (see below). You can alternatively deploy the WAR including "META-INF/context.xml" from this sample application's "war" directory. <Context path="/petclinic" docBase="/petclinic/location" ...> <!-- please note that useSystemClassLoaderAsParent is available since Tomcat 5.5.20; remove it if previous versions are being used --> <Loader loaderClass="org.springframework.instrument.classloading.tomcat.TomcatInstrumentableClassLoader" useSystemClassLoaderAsParent="false"/> ... </Context>

 

测试过程中发现，当使用tomcat 6.0.20时，在工程目录(src同级)下META-INF中追加context.xml文件，文件内容即为上诉xxxx(工程wen路径).xml文件，在MyEclipse中发布时会自动被加载到相应目录。