为什么tomcat在数据库中看不到更新？

Question

我目前在 netbeans 我用 java 开发一个 web 应用程序。我将 JPA2.0 与 H2 数据库一起使用。

问题是当我更改数据库中的数据并在浏览器中重新加载页面时=>没有设置任何更改。 仅当我在netbeans 中重新运行jsp 页面，或者我重新启动tomcat：

web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <servlet>
        <servlet-name>ajoutAutomobile</servlet-name>
        <servlet-class>controlleurs.ajoutAutomobile</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ajoutConducteur</servlet-name>
        <servlet-class>controlleurs.ajoutConducteur</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ajoutMission</servlet-name>
        <servlet-class>controlleurs.ajoutMission</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ajoutUtilisateur</servlet-name>
        <servlet-class>controlleurs.ajoutUtilisateur</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectCinConducteur</servlet-name>
        <servlet-class>controlleurs.selectCinConducteur</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectIdAuto</servlet-name>
        <servlet-class>controlleurs.selectIdAuto</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectIdAutomobile</servlet-name>
        <servlet-class>controlleurs.selectIdAutomobile</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ajoutVignette</servlet-name>
        <servlet-class>controlleurs.ajoutVignette</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectImei</servlet-name>
        <servlet-class>controlleurs.selectImei</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ajoutAssurance</servlet-name>
        <servlet-class>controlleurs.ajoutAssurance</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ajoutVisite</servlet-name>
        <servlet-class>controlleurs.ajoutVisite</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ajoutIntervention</servlet-name>
        <servlet-class>controlleurs.ajoutIntervention</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectAutoLibre</servlet-name>
        <servlet-class>controlleurs.selectAutoLibre</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectConducteurLibre</servlet-name>
        <servlet-class>controlleurs.selectConducteurLibre</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>afficheInfoGeo</servlet-name>
        <servlet-class>controlleurs.afficheInfoGeo</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>ajoutAffectation</servlet-name>
        <servlet-class>controlleurs.ajoutAffectation</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>afficheListConducteur</servlet-name>
        <servlet-class>controlleurs.afficheListConducteur</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>afficheInfoGeoRestreinte</servlet-name>
        <servlet-class>controlleurs.afficheInfoGeoRestreinte</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectDate</servlet-name>
        <servlet-class>controlleurs.selectDate</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectCoordsRestreinte</servlet-name>
        <servlet-class>controlleurs.selectCoordsRestreinte</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectAssuranceExpir</servlet-name>
        <servlet-class>controlleurs.selectAssuranceExpir</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectVignetteExpir</servlet-name>
        <servlet-class>controlleurs.selectVignetteExpir</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectVisiteExpir</servlet-name>
        <servlet-class>controlleurs.selectVisiteExpir</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectAssurance</servlet-name>
        <servlet-class>controlleurs.selectAssurance</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectVignette</servlet-name>
        <servlet-class>controlleurs.selectVignette</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>selectVisite</servlet-name>
        <servlet-class>controlleurs.selectVisite</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>afficheListAutomobile</servlet-name>
        <servlet-class>controlleurs.afficheListAutomobile</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>historiqueAffectationConducteur</servlet-name>
        <servlet-class>controlleurs.historiqueAffectationConducteur</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>historiqueAffectationAutomobile</servlet-name>
        <servlet-class>controlleurs.historiqueAffectationAutomobile</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ajoutAutomobile</servlet-name>
        <url-pattern>/ajoutAutomobile</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ajoutConducteur</servlet-name>
        <url-pattern>/ajoutConducteur</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ajoutMission</servlet-name>
        <url-pattern>/ajoutMission</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ajoutUtilisateur</servlet-name>
        <url-pattern>/ajoutUtilisateur</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectCinConducteur</servlet-name>
        <url-pattern>/selectCinConducteur</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectIdAuto</servlet-name>
        <url-pattern>/selectIdAuto</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectIdAutomobile</servlet-name>
        <url-pattern>/selectIdAutomobile</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ajoutVignette</servlet-name>
        <url-pattern>/ajoutVignette</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectImei</servlet-name>
        <url-pattern>/selectImei</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ajoutAssurance</servlet-name>
        <url-pattern>/ajoutAssurance</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ajoutVisite</servlet-name>
        <url-pattern>/ajoutVisite</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ajoutIntervention</servlet-name>
        <url-pattern>/ajoutIntervention</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectAutoLibre</servlet-name>
        <url-pattern>/selectAutoLibre</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectConducteurLibre</servlet-name>
        <url-pattern>/selectConducteurLibre</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>afficheInfoGeo</servlet-name>
        <url-pattern>/afficheInfoGeo</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>ajoutAffectation</servlet-name>
        <url-pattern>/ajoutAffectation</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>afficheListConducteur</servlet-name>
        <url-pattern>/afficheListConducteur</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>afficheInfoGeoRestreinte</servlet-name>
        <url-pattern>/afficheInfoGeoRestreinte</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectDate</servlet-name>
        <url-pattern>/selectDate</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectCoordsRestreinte</servlet-name>
        <url-pattern>/selectCoordsRestreinte</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectAssuranceExpir</servlet-name>
        <url-pattern>/selectAssuranceExpir</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectVignetteExpir</servlet-name>
        <url-pattern>/selectVignetteExpir</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectVisiteExpir</servlet-name>
        <url-pattern>/selectVisiteExpir</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectAssurance</servlet-name>
        <url-pattern>/selectAssurance</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectVignette</servlet-name>
        <url-pattern>/selectVignette</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>selectVisite</servlet-name>
        <url-pattern>/selectVisite</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>afficheListAutomobile</servlet-name>
        <url-pattern>/afficheListAutomobile</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>historiqueAffectationConducteur</servlet-name>
        <url-pattern>/historiqueAffectationConducteur</url-pattern>
    </servlet-mapping>
    <servlet-mapping>
        <servlet-name>historiqueAffectationAutomobile</servlet-name>
        <url-pattern>/historiqueAffectationAutomobile</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>
           30
        </session-timeout>
    </session-config>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

server.xml：

<?xml version='1.0' encoding='utf-8'?>
<!--
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<!-- Note:  A "Server" is not itself a "Container", so you may not
     define subcomponents such as "Valves" at this level.
     Documentation at /docs/config/server.html
 -->
<Server port="8005" shutdown="SHUTDOWN">

  <!--APR library loader. Documentation at /docs/apr.html -->
  <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />
  <!--Initialize Jasper prior to webapps are loaded. Documentation at /docs/jasper-howto.html -->
  <Listener className="org.apache.catalina.core.JasperListener" />
  <!-- Prevent memory leaks due to use of particular java/javax APIs-->
  <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" />
  <!-- JMX Support for the Tomcat server. Documentation at /docs/non-existent.html -->
  <Listener className="org.apache.catalina.mbeans.ServerLifecycleListener" />
  <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />

  <!-- Global JNDI resources
       Documentation at /docs/jndi-resources-howto.html
  -->
  <GlobalNamingResources>
    <!-- Editable user database that can also be used by
         UserDatabaseRealm to authenticate users
    -->
    <Resource name="UserDatabase" auth="Container"
              type="org.apache.catalina.UserDatabase"
              description="User database that can be updated and saved"
              factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
              pathname="conf/tomcat-users.xml" />
  </GlobalNamingResources>

  <!-- A "Service" is a collection of one or more "Connectors" that share
       a single "Container" Note:  A "Service" is not itself a "Container", 
       so you may not define subcomponents such as "Valves" at this level.
       Documentation at /docs/config/service.html
   -->
  <Service name="Catalina">

    <!--The connectors can use a shared executor, you can define one or more named thread pools-->
    <!--
    <Executor name="tomcatThreadPool" namePrefix="catalina-exec-" 
        maxThreads="150" minSpareThreads="4"/>
    -->


    <!-- A "Connector" represents an endpoint by which requests are received
         and responses are returned. Documentation at :
         Java HTTP Connector: /docs/config/http.html (blocking & non-blocking)
         Java AJP  Connector: /docs/config/ajp.html
         APR (HTTP/AJP) Connector: /docs/apr.html
         Define a non-SSL HTTP/1.1 Connector on port 8080
    -->
    <Connector port="8080" protocol="HTTP/1.1" 
               connectionTimeout="20000" 
               redirectPort="8443" />
    <!-- A "Connector" using the shared thread pool-->
    <!--
    <Connector executor="tomcatThreadPool"
               port="8080" protocol="HTTP/1.1" 
               connectionTimeout="20000" 
               redirectPort="8443" />
    -->           
    <!-- Define a SSL HTTP/1.1 Connector on port 8443
         This connector uses the JSSE configuration, when using APR, the 
         connector should be using the OpenSSL style configuration
         described in the APR documentation -->
    <!--
    <Connector port="8443" protocol="HTTP/1.1" SSLEnabled="true"
               maxThreads="150" scheme="https" secure="true"
               clientAuth="false" sslProtocol="TLS" />
    -->

    <!-- Define an AJP 1.3 Connector on port 8009 -->
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />


    <!-- An Engine represents the entry point (within Catalina) that processes
         every request.  The Engine implementation for Tomcat stand alone
         analyzes the HTTP headers included with the request, and passes them
         on to the appropriate Host (virtual host).
         Documentation at /docs/config/engine.html -->

    <!-- You should set jvmRoute to support load-balancing via AJP ie :
    <Engine name="Catalina" defaultHost="localhost" jvmRoute="jvm1">         
    --> 
    <Engine name="Catalina" defaultHost="localhost">

      <!--For clustering, please take a look at documentation at:
          /docs/cluster-howto.html  (simple how to)
          /docs/config/cluster.html (reference documentation) -->
      <!--
      <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>
      -->        

      <!-- The request dumper valve dumps useful debugging information about
           the request and response data received and sent by Tomcat.
           Documentation at: /docs/config/valve.html -->
      <!--
      <Valve className="org.apache.catalina.valves.RequestDumperValve"/>
      -->

      <!-- This Realm uses the UserDatabase configured in the global JNDI
           resources under the key "UserDatabase".  Any edits
           that are performed against this UserDatabase are immediately
           available for use by the Realm.  -->
      <Realm className="org.apache.catalina.realm.UserDatabaseRealm"
             resourceName="UserDatabase"/>

      <!-- Define the default virtual host
           Note: XML Schema validation will not work with Xerces 2.2.
       -->
      <Host name="localhost"  appBase="webapps"
            unpackWARs="true" autoDeploy="true"
            xmlValidation="false" xmlNamespaceAware="false">

        <!-- SingleSignOn valve, share authentication between web applications
             Documentation at: /docs/config/valve.html -->
        <!--
        <Valve className="org.apache.catalina.authenticator.SingleSignOn" />
        -->

        <!-- Access log processes all example.
             Documentation at: /docs/config/valve.html -->
        <!--
        <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"  
               prefix="localhost_access_log." suffix=".txt" pattern="common" resolveHosts="false"/>
        -->

      </Host>
    </Engine>
  </Service>
</Server>

请问这个问题怎么解决？

编辑：我尝试删除缓存，也在其他浏览器中打开页面=>同样的结果..

EDIT2： 持久性.xml：

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
  <persistence-unit name="webPU" transaction-type="RESOURCE_LOCAL">
    <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
    <class>entities.Automobile</class>
    <class>entities.Intervention</class>
    <class>entities.Assurance</class>
    <class>entities.Coordonnees</class>
    <class>entities.Mission</class>
    <class>entities.Affectation</class>
    <class>entities.Conducteur</class>
    <class>entities.Gps</class>
    <class>entities.Vignette</class>
    <class>entities.Utilisateur</class>
    <class>entities.VisiteTechnique</class>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties>
      <property name="javax.persistence.jdbc.url" value="jdbc:h2:tcp://localhost/~/ApiGps"/>
      <property name="javax.persistence.jdbc.password" value=""/>
      <property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
      <property name="javax.persistence.jdbc.user" value="sa"/>
    </properties>
  </persistence-unit>
</persistence>

我的小服务程序：

response.setContentType("application/json");

        PrintWriter out = response.getWriter();
        EntityManagerFactory emf=Persistence.createEntityManagerFactory("webPU"); 


       Timestamp nd=new Timestamp(System.currentTimeMillis());//now
       nd.setMinutes(nd.getMinutes()-20);
      EntityManager em=emf.createEntityManager();
      String req="select a from Automobile a where a.gpsImei.imei in (SELECT c.gpsImei.imei FROM Coordonnees c WHERE c.date < :nd )";
      Query resultat=em.createQuery(req);
      resultat.setParameter("nd", nd);
      java.util.List<Automobile> la= resultat.getResultList();  
      Gson gson=new Gson();
      String json =gson.toJson(La);//convert the List to json

      try {
        out.println(json);//return respons to ajax
       } finally {            
        out.close();
       }

Answer 1

由于您使用的是transaction-type="RESOURCE_LOCAL"

您总是希望只使用一个 EntityManager。有一个父类在您的应用程序中管理相同的 EntityManager 实例。

拥有多个实例几乎从来都不是一个好主意 EntityManager 正在使用（不要创建第二个，除非你已经 摧毁第一个）

我认为问题在于在这里创建一个新的 EM

EntityManager em=emf.createEntityManager();

个人更喜欢使用事务类型，transaction-type="TRANSACTION"，不用担心实体管理器https://stackoverflow.com/a/1963012/643500

您可以在这里阅读更多内容http://openejb.apache.org/jpa-concepts.html

当你保存数据时，你是使用 saveOrUpdate 还是 merge？

这可能不是正确的答案，但我希望它有所帮助。