java ServletException: 没有指定 servlet 类
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ServletException: No servlet class has been specified
提问by David Felton
I have what should be an extremely simple "Hello World" servlet, but I cannot get it to work. I am using Eclipse, Tomcat 8, Java 7, and Servlet 3.1.
我有一个非常简单的“Hello World”servlet，但我无法让它工作。我正在使用 Eclipse、Tomcat 8、Java 7 和 Servlet 3.1。
I have looked at many tutorials and questions, but they have not completely helped. Most tutorials I have seen talk about creating servlets by extending HttpServlet. I got those to work. Now I'd like to try the cleaner annotation approach.
我看过很多教程和问题，但它们并没有完全帮助。我看过的大多数教程都在讨论通过扩展 HttpServlet 来创建 servlet。我让那些工作。现在我想尝试更简洁的注释方法。
I've been referring to this tutorial, but it isn't quite complete and seems to have some incorrect or incomplete examples: Packaging and Deploying RESTful Web Services
我一直在参考这个教程，但它不是很完整，似乎有一些不正确或不完整的例子： 打包和部署 RESTful Web 服务
Why is com.testing.service.MyApplication not being loaded?
为什么没有加载 com.testing.service.MyApplication？
Any help on getting this thing to run would be immensely appreciated!
任何有关让这个东西运行的帮助将不胜感激！
Here are my files:
这是我的文件：
MyApplication.java
我的应用程序
package com.testing.service;
import java.util.HashSet;
import java.util.Set;
import javax.ws.rs.ApplicationPath;
import javax.ws.rs.core.Application;
@ApplicationPath("app")
public class MyApplication extends Application {
public Set<Class<?>> getClasses() {
Set<Class<?>> s = new HashSet<Class<?>>();
s.add(HelloWorldResource.class);
return s;
}
}
HelloWorldResource.java
HelloWorldResource.java
package com.testing.service;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
@Path("/helloworld")
public class HelloWorldResource {
@SuppressWarnings("unused")
private static final long serialVersionUID = 1L;
@GET
@Produces("text/plain")
public String sayHello() {
return "Hello World!";
}
}
web.xml
网页.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app
xmlns="http://xmlns.jcp.org/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1">
<display-name>service</display-name>
<servlet>
<servlet-name>com.testing.service.MyApplication</servlet-name>
<init-param>
<param-name>javax.ws.rs.Application</param-name>
<param-value>com.testing.service.MyApplication</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
</web-app>
pom.xml
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.testing</groupId>
<artifactId>service</artifactId>
<version>1.0</version>
<packaging>war</packaging>
<name>Rest Test</name>
<dependencies>
<dependency>
<groupId>javax.ws.rs</groupId>
<artifactId>javax.ws.rs-api</artifactId>
<version>2.0.1</version>
</dependency>
</dependencies>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</pluginManagement>
</build>
</project>
Whenever I run Tomcat, it displays the following error:
每当我运行 Tomcat 时，它都会显示以下错误：
INFO: Marking servlet com.testing.service.MyApplication as unavailable
Feb 05, 2015 3:28:55 PM org.apache.catalina.core.StandardContext loadOnStartup
SEVERE: Servlet /service threw load() exception
javax.servlet.ServletException: No servlet class has been specified for servlet com.testing.service.MyApplication
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1099)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:1041)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4944)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5230)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1409)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1399)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
采纳答案by David Felton
I found the answer in the comments of a related question. The answer was provided by Alvin Thompson. Unfortunately, I don't have enough reputation to up-vote your answer.
我在一个相关问题的评论中找到了答案。答案由阿尔文·汤普森提供。不幸的是，我没有足够的声誉来为您的答案投票。
If you're using a standard Tomcat install (or some other servlet container), you need to include a REST implementation since Tomcat doesn't come with one. If you're using Maven, add this to the dependencies section:
<dependencies> <dependency> <groupId>org.glassfish.jersey.bundles</groupId> <artifactId>jaxrs-ri</artifactId> <version>2.13</version> </dependency> ... </dependencies>Then just add an application config class to your project. If you don't have any special configuration needs aside from setting the context path for the rest services, the class can be empty. Once this class is added, you don't need to configure anything in web.xml (or have one at all).
如果您使用标准的 Tomcat 安装（或其他一些 servlet 容器），您需要包含一个 REST 实现，因为 Tomcat 没有提供。如果您使用的是 Maven，请将其添加到依赖项部分：
<dependencies> <dependency> <groupId>org.glassfish.jersey.bundles</groupId> <artifactId>jaxrs-ri</artifactId> <version>2.13</version> </dependency> ... </dependencies>然后只需在您的项目中添加一个应用程序配置类。如果除了为其余服务设置上下文路径之外没有任何特殊的配置需求，则该类可以为空。一旦添加了这个类，你就不需要在 web.xml 中配置任何东西（或者根本不需要）。
Originally posted here:
原贴在这里：
How to set up JAX-RS Application using annotations only (no web.xml)?
