我是JavaEE的新手，目前正在学习JavaEE7。我安装了JavaEE7并下载了NetBeans 8.0.2，因此我可以通过此处发布的网络研讨会来关注：
https://www.youtube.com/watch?v=sCNslREYpD0&spfreload=10
视频中的本教程使用JavaEE6而不是JavaEE7。
在我遇到帖子标题中提到的java.lang.IllegalStateException之前，我在网络研讨会上花了大约12分钟。在视频的12:18处，演示者会在代码中添加@PersistenceUnit，然后在EntityManagerFactory中添加java.lang.IllegalStateException: Unable to retrieve EntityManagerFactory for unitName null
at com.sun.enterprise.container.common.impl.EntityManagerFactoryWrapper.getDelegate(EntityManagerFactoryWrapper.java:103)
at com.sun.enterprise.container.common.impl.EntityManagerFactoryWrapper.createEntityManager(EntityManagerFactoryWrapper.java:114)
at org.glasssfish.samples.TestServlet.processRequest(TestServlet.java:79)
at org.glasssfish.samples.TestServlet.doGet(TestServlet.java:103)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:687)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Thread.java:745)
。虽然我非常仔细地阅读了他的教程，但我遇到了持久性问题，并且一直遇到以下异常：
persistence.xml我广泛搜索StackOverflow和Google，我不断遇到的答案与persistence.xml文件的位置有关。我使用NetBeans自动创建并将Configuration Files文件放在Web Pages
WEB-INF
index.html
Source Packages
org.glassfish.samples
TestServlet.java
org.glassfish.samples.model
Friend.java
Libraries
JDK 1.8 (Default)
GlassFish Server 4.1
Configuration Files
MANIFEST.MF
persistence.xml
文件夹中。
NetBeans 8.0.2中的项目布局如下所示：
Friend.java以下是NetBeans作为教程的一部分自动生成的/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package org.glasssfish.samples.model;
import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import javax.xml.bind.annotation.XmlRootElement;
/**
*
* @author james
*/
@Entity
@Table(name = "FRIEND")
@XmlRootElement
@NamedQueries({
@NamedQuery(name = "Friend.findAll", query = "SELECT f FROM Friend f"),
@NamedQuery(name = "Friend.findByName", query = "SELECT f FROM Friend f WHERE f.name = :name"),
@NamedQuery(name = "Friend.findByAge", query = "SELECT f FROM Friend f WHERE f.age = :age")})
public class Friend implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Basic(optional = false)
@NotNull
@Size(min = 1, max = 30)
@Column(name = "NAME")
private String name;
@Column(name = "AGE")
private Integer age;
public Friend() {
}
public Friend(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public int hashCode() {
int hash = 0;
hash += (name != null ? name.hashCode() : 0);
return hash;
}
@Override
public boolean equals(Object object) {
// TODO: Warning - this method won't work in the case the id fields are not set
if (!(object instanceof Friend)) {
return false;
}
Friend other = (Friend) object;
if ((this.name == null && other.name != null) || (this.name != null && !this.name.equals(other.name))) {
return false;
}
return true;
}
@Override
public String toString() {
return "org.glasssfish.samples.model.Friend[ name=" + name + " ]";
}
}
文件：
TestServlet.java以下是/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package org.glasssfish.samples;
import java.io.IOException;
import java.io.PrintWriter;
import javax.persistence.EntityManagerFactory;
import javax.persistence.PersistenceUnit;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.glasssfish.samples.model.Friend;
/**
*
* @author james
*/
@WebServlet(name = "TestServlet", urlPatterns = {"/TestServlet"})
public class TestServlet extends HttpServlet {
@PersistenceUnit
EntityManagerFactory emf;
/**
* Processes requests for both HTTP <code>GET</code> and <code>POST</code>
* methods.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=UTF-8");
try (PrintWriter out = response.getWriter()) {
/* TODO output your page here. You may use following sample code. */
out.println("<!DOCTYPE html>");
out.println("<html>");
out.println("<head>");
out.println("<title>Servlet TestServlet</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Servlet TestServlet at " + request.getContextPath() + "</h1>");
//
int count;
if (request.getSession().getAttribute("count") == null) {
count = 0;
} else {
count = (Integer)request.getSession().getAttribute("count");
}
request.getSession().setAttribute("count", ++count);
out.println("Accessed again: " + request.getSession().getAttribute("count"));
Friend f = (Friend)emf.createEntityManager().createNamedQuery("Friend.findAll").getResultList().get(0);
out.println("Friend name: " + f.getName());
out.println("</body>");
out.println("</html>");
}
}
// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
* Handles the HTTP <code>GET</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
/**
* Handles the HTTP <code>POST</code> method.
*
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
processRequest(request, response);
}
/**
* Returns a short description of the servlet.
*
* @return a String containing servlet description
*/
@Override
public String getServletInfo() {
return "Short description";
}// </editor-fold>
}
文件：
persistence.xml当然，NetBeans 8.0.2自动生成的看似臭名昭着的<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="JavaEE7WebinarPU" transaction-type="JTA">
<jta-data-source>jdbc/sample</jta-data-source>
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<properties/>
</persistence-unit>
</persistence>
文件：
PersistenceContext我尝试过各种各样的事情：
注入PersistenceUnit代替EntityManager并直接从那里获取EntityManagerFactor而不是使用@PersistenceUnit（不确定我是否正确执行了此操作）
将@PersistenceUnit(unitName="JavaEE7WebinarPU")修改为java.lang.IllegalStateException: Unable to retrieve EntityManagerFactory for unitName null。这并没有多大帮助。它只是改变了我的错误：
java.lang.IllegalStateException: Unable to retrieve EntityManagerFactory for unitName JavaEE7WebinarPU
到
jdbc/sample
SamplePool的资源，该资源映射到名为SamplePool的池。我还验证了我的GlassFish服务器有一个名为javax.sql.DataSource的连接池。它目前设置为Clean and Build资源类型。我希望有更多JavaEE经验的人可以指出我在这里遗漏的明显事实。或者也许是从JavaEE6变为JavaEE7的东西，这可能是我的错误的原因。
非常感谢任何帮助或建议。
/
更新：我刚刚在NetBeans中运行warning: Supported source version 'RELEASE_6' from annotation processor 'org.eclipse.persistence.internal.jpa.modelgen.CanonicalModelProcessor' less than -source '1.8'`
并看到以下警告：
/
{{1}}
我安装了JDK 1.8（更新31），NetBeans 8.0.2和GlassFish 4.1。这个警告是否表明eclipseLink不能使用JDK 1.8？
/ UPDATE＃2：好吧，这似乎是一个非常蹩脚的决议。在尝试解决这个问题几个小时之后。我关闭了我的GlassFish服务器，断开了与数据库的连接，执行了“清理和构建”，重新启动了所有内容并重新部署。现在一切似乎都在按照我的预期发挥作用。我想某些东西在某个地方有点不稳定，而且只有一个干净的＆＃39;能够解决这个问题。啊。 /
答案 0 :(得分：1)
显然我构建的东西有点时髦。我关闭了所有服务器，执行了清理和构建并重新部署。现在，一切似乎都在起作用。
感谢大家的建议。
答案 1 :(得分：0)
我在persistence.xml中发现缺少的是提供程序。在persistence-unit元素中，还添加以下标记
<provider> provider_name</provider>
检查您正在使用的提供商
答案 2 :(得分：0)
您已在帖子中指定了实体管理员，并且您尝试访问实体管理器两者都不同请参阅 你应该这样做
@PersistenceContext(name="entiyManager")
EntityManager entitymanager;
您还需要初始化您的实体管理工厂
答案 3 :(得分：0)
詹姆斯，我认为这是一个简单的解决方案。 改变
@PersistenceUnit
到
@PersistenceUnit(unitName="JavaEE7WebinarPU")
另见https://docs.oracle.com/javaee/6/api/javax/persistence/PersistenceUnit.html
答案 4 :(得分：0)
没问题哥们很容易在persistence.xml文件中添加它
<?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="JavaEE7WebinarPU" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>jdbc/sample</jta-data-source>
<properties>
<property name="eclipselink.ddl-generation" value="create-tables"/>
</properties>
</persistence-unit>
</persistence>
您可以选择netbeans生成的持久性类来命名持久性单元。在命名后，只需做一个干净的构建，你就会得到答案。