detached entity passed to persist

JPA 持久化问题

描述 :使用spring+strust2配置，第一次新增成功，第二次新增抛异常

HTTP Status 500 -
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: model.Product; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: model.Product
    org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:648)
    org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:95)
    org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:212)
    org.springframework.orm.jpa.JpaAccessor.translateIfNecessary(JpaAccessor.java:152)
    org.springframework.orm.jpa.JpaTemplate.execute(JpaTemplate.java:189)
    org.springframework.orm.jpa.JpaTemplate.persist(JpaTemplate.java:266)
root cause
org.hibernate.PersistentObjectException: detached entity passed to persist: model.Product
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.26 logs.
Apache Tomcat/6.0.26

方案一 (推荐)

设置spring配置文件，使每次请求都重新初始化变量

    <bean id="demoAction" class="com.web.action.DemoAction" scope="prototype"></bean>

方案二

在新增的Jsp页面隐藏对应的ID字段，使其值为零

<input type="hidden" name="bean.id" value="0" />

方案三

在执行方法体内，对刚刚持久化的实体手工初始化

public String  execute throw Exception {

      demoService.addBean(bean);
      DemoBean = new DemoBean ();

}

另 如果 action在单实例时，只要程序异常，是无法再次执行，推荐Action使用 scope="prototype"

HTTP Status 404 - No result defined for action com.web.action.DemoAction and result input

type Status report

message No result defined for action com.web.action.DemoAction and result input

description The requested resource (No result defined for action com.web.action.DemoAction and result input) is not available.