HTTP Status 500 - Could not write content: could not initialize proxy - no Session
原因:EntityManager提前关闭了
解决方案:在web.xml中配置Spring的过滤器
<!--解决no-session的问题-->
<filter>
<filter-name>openEntityManager</filter-name>
<filter-class>org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>openEntityManager</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>