java - Rest API java : java. lang.ClassNotFoundException : com. tutorialspoint.User

Question

我是 Java 和 REST API 的新手，我遇到了以下问题。我点击那个链接 https://www.tutorialspoint.com/restful/restful_first_application.htm了解如何构建 REST API。我尝试了一些东西，我想使用我自己的包 (com.ca) 并将我的 web.xml 更新为以下内容:

<?xml version = "1.0" encoding = "UTF-8"?> 
<web-app xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"  
   xmlns = "http://java.sun.com/xml/ns/javaee"  
   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee  
   http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"  
   id = "WebApp_ID" version = "3.0"> 
   <display-name>User Management</display-name> 
   <servlet> 
      <servlet-name>Jersey RESTful Application</servlet-name> 
      <servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class> 
      <init-param> 
         <param-name>jersey.config.server.provider.packages</param-name> 
         <param-value>com.ca</param-value> 
      </init-param> 
   </servlet> 
   <servlet-mapping> 
      <servlet-name>Jersey RESTful Application</servlet-name> 
      <url-pattern>/rest/*</url-pattern> 
   </servlet-mapping>
</web-app>

然而，当我尝试在服务器上重新运行代码并执行 GET 请求时，我获得了以下信息:

java.lang.ClassNotFoundException: com.tutorialspoint.User
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1892)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1735)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:677)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1826)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1713)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2000)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1535)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:422)
    at java.util.ArrayList.readObject(ArrayList.java:791)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:1058)
    at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:2136)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2027)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1535)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:422)
    at com.ca.UserDao.getAllUsers(UserDao.java:28)
    at com.ca.UserService.getUsers(UserService.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory.lambda$static$0(ResourceMethodInvocationHandlerFactory.java:76)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:148)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:191)
    at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$TypeOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:243)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:103)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:493)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:415)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:104)
    at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:277)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:272)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:268)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:316)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:298)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:268)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:289)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:256)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:703)
    at org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:416)
    at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:370)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:389)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:342)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:229)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

它似乎仍然指向以前的包(用于练习的那个)，但我找不到为什么......另外，如果你有关于它的有用链接(如何设置 web.xml，每个标签角色,...) 这也会有帮助。

提前致谢。

更新:以下是源文件:用户.java:

package com.ca;

import java.io.Serializable;  
import javax.xml.bind.annotation.XmlElement; 
import javax.xml.bind.annotation.XmlRootElement; 
@XmlRootElement(name = "user") 

public class User implements Serializable {  
   private static final long serialVersionUID = 1L; 
   private int id; 
   private String name; 
   private String profession;  
   public User(){} 

   public User(int id, String name, String profession){  
      this.id = id; 
      this.name = name; 
      this.profession = profession; 
   }  
   public int getId() { 
      return id; 
   }  
   @XmlElement 
   public void setId(int id) { 
      this.id = id; 
   } 
   public String getName() { 
      return name; 
   } 
   @XmlElement
   public void setName(String name) { 
      this.name = name; 
   } 
   public String getProfession() { 
      return profession; 
   } 
   @XmlElement 
   public void setProfession(String profession) { 
      this.profession = profession; 
   }   
} 

用户道.java:

package com.ca;  

import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileNotFoundException;  
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.ObjectInputStream; 
import java.io.ObjectOutputStream; 
import java.util.ArrayList; 
import java.util.List;  

public class UserDao { 
   public List<User> getAllUsers(){ 

      List<User> userList = null; 
      try { 
         File file = new File("Users.dat"); 
         if (!file.exists()) { 
            User user = new User(1, "Mahesh", "Teacher"); 
            userList = new ArrayList<User>(); 
            userList.add(user); 
            saveUserList(userList); 
         } 
         else{ 
            FileInputStream fis = new FileInputStream(file); 
            ObjectInputStream ois = new ObjectInputStream(fis); 
            userList = (List<User>) ois.readObject(); 
            ois.close(); 
         } 
      } catch (IOException e) { 
         e.printStackTrace(); 
      } catch (ClassNotFoundException e) { 
         e.printStackTrace(); 
      }   
      return userList; 
   } 
   private void saveUserList(List<User> userList){ 
      try { 
         File file = new File("Users.dat"); 
         FileOutputStream fos;  
         fos = new FileOutputStream(file); 
         ObjectOutputStream oos = new ObjectOutputStream(fos); 
         oos.writeObject(userList); 
         oos.close(); 
      } catch (FileNotFoundException e) { 
         e.printStackTrace(); 
      } catch (IOException e) { 
         e.printStackTrace(); 
      } 
   }    
}

用户服务.java:

package com.ca;

import java.util.List; 
import javax.ws.rs.GET; 
import javax.ws.rs.Path; 
import javax.ws.rs.Produces; 
import javax.ws.rs.core.MediaType;  
@Path("/UserService") 

public class UserService {  
   UserDao userDao = new UserDao();  
   @GET 
   @Path("/users") 
   @Produces(MediaType.APPLICATION_XML) 
   public List<User> getUsers(){ 
      return userDao.getAllUsers(); 
   }  
}

更新 2.0: Screenshot of the project folder

现在我有以下内容:

<html>
    <head>
        <title>Apache Tomcat/7.0.81 - Error report</title>
        <style>
            <!--H1 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:22px;} H2 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:16px;} H3 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:14px;} BODY {font-family:Tahoma,Arial,sans-serif;color:black;background-color:white;} B {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;} P {font-family:Tahoma,Arial,sans-serif;background:white;color:black;font-size:12px;}A {color : black;}A.name {color : black;}HR {color : #525D76;}-->
        </style>
    </head>
    <body>
        <h1>HTTP Status 404 - /REST-Example/rest/UserService/users</h1>
        <HR size="1" noshade="noshade">
        <p>
            <b>type</b> Status report
        </p>
        <p>
            <b>message</b>
            <u>/REST-Example/rest/UserService/users</u>
        </p>
        <p>
            <b>description</b>
            <u>The requested resource is not available.</u>
        </p>
        <HR size="1" noshade="noshade">
        <h3>Apache Tomcat/7.0.81</h3>
    </body>
</html>

Answer 1

您可能遗漏了一些步骤。我只是按照教程进行操作，一切正常。以下是我所做的:

1. 根据教程网站上的说明配置您的系统。
2. 创建 Eclipse 动态 Web 项目
3. 下载 Jersey 2.17 并根据教程站点上的说明在目录中展开它。
4. 将除 javax.servlet-api-3.0.1.jar 之外的所有 JAR 文件复制到 WEB-INF/lib 文件夹中。
5. 创建类 User.java、UserDao.java、UserService.java 和 web.xml文件夹，如屏幕截图所示。
6. 右键单击项目(在我的示例中:REST-Example)并选择Export>WAR file 将项目导出到 war 文件。
7. 将war文件复制到Tomcat的webapps文件夹下并启动。
8. 启动您选择的浏览器并调用 http://localhost:8080/REST-Example/rest/UserService/users ，其中 REST-Example 是没有文件扩展名的 war 文件的名称。

如果您使用 Maven，甚至会更简单:您需要添加一两个依赖项，Maven 会处理其余部分。