簡單的REST API返回HTTP 500

我正在嘗試製作一個簡單的Hello World REST API。我使用IntelliJ IDEA作爲我的IDE。我已經下載了Tomcat 8.5.4以用作我的本地測試服務器。如果有關係，我正在Mac上開發。我有澤西庫進口：簡單的REST API返回HTTP 500

這裏是我的web.xml文件：

<?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>HelloWorld</display-name> 
    <servlet> 
     <servlet-name>com.jamesshinevar.HelloWorld</servlet-name> 
     <init-param> 
      <param-name>jersey.config.server.provider.packages</param-name> 
      <param-value>com.jamesshinevar</param-value> 
     </init-param> 
    </servlet> 

    <servlet-mapping> 
     <servlet-name>com.jamesshinevar.HelloWorld</servlet-name> 
     <url-pattern>/api/*</url-pattern> 
    </servlet-mapping> 
</web-app>

這裏是我的類代碼：

package com.jamesshinevar; 

import javax.ws.rs.GET; 
import javax.ws.rs.Path; 
import javax.ws.rs.Produces; 
import javax.ws.rs.core.MediaType; 

@Path("/test") 
public class HelloWorld { 
    @GET 
    @Produces(MediaType.TEXT_PLAIN) 
    public String hello(){ 
     return "Hello"; 
    } 
}

我然後運行這個和我得到它正在運行的指示如下：

/Users/james/apache-tomcat-8.5.4/bin/catalina.sh run 
[2016-08-16 09:33:11,573] Artifact helloworldREST:war exploded: Server is not connected. Deploy is not available. 
16-Aug-2016 09:33:12.907 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Server version:  Apache Tomcat/8.5.4 
16-Aug-2016 09:33:12.909 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Server built:   Jul 6 2016 08:43:30 UTC 
16-Aug-2016 09:33:12.909 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Server number:   8.5.4.0 
16-Aug-2016 09:33:12.909 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log OS Name:    Mac OS X 
16-Aug-2016 09:33:12.909 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log OS Version:   10.11.6 
16-Aug-2016 09:33:12.909 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Architecture:   x86_64 
16-Aug-2016 09:33:12.909 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Java Home:    /Library/Java/JavaVirtualMachines/jdk1.8.0_101.jdk/Contents/Home/jre 
16-Aug-2016 09:33:12.909 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log JVM Version:   1.8.0_101-b13 
16-Aug-2016 09:33:12.910 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log JVM Vendor:   Oracle Corporation 
16-Aug-2016 09:33:12.910 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log CATALINA_BASE:   /Users/james/Library/Caches/IntelliJIdea2016.2/tomcat/Tomcat_8_5_4_helloworldREST_4 
16-Aug-2016 09:33:12.910 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log CATALINA_HOME:   /Users/james/apache-tomcat-8.5.4 
16-Aug-2016 09:33:12.911 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djava.util.logging.config.file=/Users/james/Library/Caches/IntelliJIdea2016.2/tomcat/Tomcat_8_5_4_helloworldREST_4/conf/logging.properties 
16-Aug-2016 09:33:12.911 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager 
16-Aug-2016 09:33:12.911 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Dcom.sun.management.jmxremote= 
16-Aug-2016 09:33:12.911 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Dcom.sun.management.jmxremote.port=1099 
16-Aug-2016 09:33:12.911 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Dcom.sun.management.jmxremote.ssl=false 
16-Aug-2016 09:33:12.911 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Dcom.sun.management.jmxremote.authenticate=false 
16-Aug-2016 09:33:12.912 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djava.rmi.server.hostname=127.0.0.1 
16-Aug-2016 09:33:12.912 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djdk.tls.ephemeralDHKeySize=2048 
16-Aug-2016 09:33:12.912 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Dcatalina.base=/Users/james/Library/Caches/IntelliJIdea2016.2/tomcat/Tomcat_8_5_4_helloworldREST_4 
16-Aug-2016 09:33:12.912 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Dcatalina.home=/Users/james/apache-tomcat-8.5.4 
16-Aug-2016 09:33:12.912 INFO [main] org.apache.catalina.startup.VersionLoggerListener.log Command line argument: -Djava.io.tmpdir=/Users/james/apache-tomcat-8.5.4/temp 
16-Aug-2016 09:33:12.912 INFO [main] org.apache.catalina.core.AprLifecycleListener.lifecycleEvent The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: /Users/james/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:. 
16-Aug-2016 09:33:13.174 INFO [main] org.apache.coyote.AbstractProtocol.init Initializing ProtocolHandler ["http-nio-8080"] 
16-Aug-2016 09:33:13.210 INFO [main] org.apache.tomcat.util.net.NioSelectorPool.getSharedSelector Using a shared selector for servlet write/read 
16-Aug-2016 09:33:13.214 INFO [main] org.apache.coyote.AbstractProtocol.init Initializing ProtocolHandler ["ajp-nio-8009"] 
16-Aug-2016 09:33:13.216 INFO [main] org.apache.tomcat.util.net.NioSelectorPool.getSharedSelector Using a shared selector for servlet write/read 
16-Aug-2016 09:33:13.216 INFO [main] org.apache.catalina.startup.Catalina.load Initialization processed in 802 ms 
16-Aug-2016 09:33:13.250 INFO [main] org.apache.catalina.core.StandardService.startInternal Starting service Catalina 
16-Aug-2016 09:33:13.250 INFO [main] org.apache.catalina.core.StandardEngine.startInternal Starting Servlet Engine: Apache Tomcat/8.5.4 
16-Aug-2016 09:33:13.259 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler [http-nio-8080] 
16-Aug-2016 09:33:13.267 INFO [main] org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler [ajp-nio-8009] 
16-Aug-2016 09:33:13.268 INFO [main] org.apache.catalina.startup.Catalina.start Server startup in 51 ms 
Connected to server 
[2016-08-16 09:33:13,571] Artifact helloworldREST:war exploded: Artifact is being deployed, please wait... 
[2016-08-16 09:33:14,065] Artifact helloworldREST:war exploded: Artifact is deployed successfully 
[2016-08-16 09:33:14,066] Artifact helloworldREST:war exploded: Deploy took 494 milliseconds 
16-Aug-2016 09:33:23.264 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory /Users/james/apache-tomcat-8.5.4/webapps/manager 
16-Aug-2016 09:33:23.292 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory /Users/james/apache-tomcat-8.5.4/webapps/manager has finished in 28 ms

當我嘗試去網址獲取：

在Tomcat的本地主機登錄的IntelliJ我：

16-Aug-2016 09:35:39.773 SEVERE [http-nio-8080-exec-8] org.apache.catalina.core.StandardHostValve.invoke Exception Processing /helloworld/api/test 
java.lang.NullPointerException 
    at java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1011) 
    at java.util.concurrent.ConcurrentHashMap.putIfAbsent(ConcurrentHashMap.java:1535) 
    at java.lang.ClassLoader.getClassLoadingLock(ClassLoader.java:463) 
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1151) 
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1118) 
    at org.apache.catalina.core.StandardWrapper.servletSecurityAnnotationScan(StandardWrapper.java:1139) 
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:510) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) 
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) 
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:1110) 
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) 
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:785) 
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425) 
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) 
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 
    at java.lang.Thread.run(Thread.java:745)

我不明白是什麼原因造成的NullPointerException異常這是造成500錯誤。我確信它在我眼前，但我只是不理解我所看到的。任何人都可以給我一些指導，如何使這項工作？這似乎應該很簡單。我想要一個只返回「Hello」字符串的API，但顯然我很難。

來源

2016-08-16 BigDevJames

我會不同意，而我得到一個NullPointerException，我沒有看到在指向我的代碼跟蹤任何東西。不過，我會徹底閱讀你的文章並看看。 – BigDevJames

你缺少servlet-class進入

<?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>HelloWorld</display-name> 
    <servlet> 
     <servlet-name>com.jamesshinevar.HelloWorld</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.jamesshinevar</param-value> 
     </init-param> 
    </servlet> 

    <servlet-mapping> 
     <servlet-name>com.jamesshinevar.HelloWorld</servlet-name> 
     <url-pattern>/api/*</url-pattern> 
    </servlet-mapping> 
</web-app>

來源

2016-08-16 13:48:36 sidgate

這幫助我走向正確的方向。似乎在Jersey 1.x和2.x的寫法之間也存在混淆。我已經找到了更多的幫助：https://stackoverflow.com/questions/22022114/org-glassfish-jersey-servlet-servletcontainer-classnotfoundexception – BigDevJames

我需要做一個很好的教程，但我回到了開始，並做了使用maven原型的API。這加載了所有適當的庫並正確地構建了web.xml。 – BigDevJames

我相信錯誤是在web.xml中。作爲mkyong所示：

<web-app id="WebApp_ID" version="2.4" 
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> 
    <display-name>Restful Web Application</display-name> 

    <servlet> 
     <servlet-name>jersey-serlvet</servlet-name> 
     <servlet-class> 
        com.sun.jersey.spi.container.servlet.ServletContainer 
       </servlet-class> 
     <init-param> 
      <param-name>com.sun.jersey.config.property.packages</param-name> 
      <param-value>com.jamesshinevar</param-value> 
     </init-param> 
     <load-on-startup>1</load-on-startup> 
    </servlet> 

    <servlet-mapping> 
     <servlet-name>jersey-serlvet</servlet-name> 
     <url-pattern>/api/*</url-pattern> 
    </servlet-mapping> 

</web-app>

您在指定的類不是一個servlet。提供servlet並將請求映射到註釋類是澤西的工作。

來源

2016-08-16 13:48:10

您需要的<servlet-class>條目添加到web.xml，如com.sun.jersey.spi.container.servlet.ServletContainer。

欲瞭解更多信息，看看這個教程：https://www.ibm.com/developerworks/library/wa-aj-tomcat/

來源

2016-08-16 13:49:50

簡單的REST API返回HTTP 500

回答

相關問題