Gson类通过Maven导入，在部署到JSP和Servlet Java Web时找不到。

huangapple
go评论104阅读模式
英文:

Gson Class Imported by Maven is Not Found When Deployed on JSP and Servlet Java Web

问题

我通过Maven导入了Gson，其代码如下：

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <project xmlns="http://maven.apache.org/POM/4.0.0"
  3.          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  5.     <modelVersion>4.0.0</modelVersion>
  7.     <groupId>org.example</groupId>
  8.     <artifactId>HerbTea</artifactId>
  9.     <version>1.0-SNAPSHOT</version>
  10.     <!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
  11.     <dependencies>
  12.         <dependency>
  13.             <groupId>com.google.code.gson</groupId>
  14.             <artifactId>gson</artifactId>
  15.             <version>2.8.5</version>
  16.         </dependency>
  17.         <!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter-api -->
  18.         <dependency>
  19.             <groupId>org.junit.jupiter</groupId>
  20.             <artifactId>junit-jupiter-api</artifactId>
  21.             <version>5.4.0</version>
  22.             <scope>test</scope>
  23.         </dependency>
  24.         <dependency>
  25.             <groupId>org.junit.jupiter</groupId>
  26.             <artifactId>junit-jupiter-api</artifactId>
  27.             <version>5.4.0</version>
  28.             <scope>compile</scope>
  29.         </dependency>
  30.     </dependencies>
  31. </project>

然而，当我在JSP Servlet程序上运行我的程序时，我收到以下错误：

  1. java.lang.NoClassDefFoundError: com/google/gson/Gson

我不知道为什么会出现这个错误。您可以在这里查看错误报告：链接

HTTP状态500 – 内部服务器错误

类型异常报告
消息处理[/outcome.jsp]中的异常在第[21]行发生了异常
描述服务器遇到了一个意外情况，阻止了它完成请求。
异常
org.apache.jasper.JasperException：在第[21]行处处理[/outcome.jsp]中的异常

  1. 18:     <% WindowDisplay windowDisplay = (WindowDisplay) request.getSession().getAttribute("windowDisplay");
  2. 19:         System.out.println(session.getAttribute(reqSymptomParamKey));
  3. 20:         windowDisplay.getRecipeDisplay();
  4. 21:         List<Recipe> a = windowDisplay.getRecipeDisplay().retrieveCorrespondingRecipe((List<String>) session.getAttribute(reqSymptomParamKey));
  5. 22:         for (Recipe i : windowDisplay.getRecipeDisplay().retrieveCorrespondingRecipe((List<String>) session.getAttribute(reqSymptomParamKey))) {%>
  6. 23:     <p1>name:<%=i.getName()%> </p1>
  7. 24:     <p1>Corresponding Symptom: <%=i.getSymptomNameList()%></p1>

堆栈跟踪：
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:617)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:499)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
com.web.servlet.ServerServlet.doPost(ServerServlet.java:60)
javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
根本原因
javax.servlet.ServletException：java.lang.NoClassDefFoundError：com/google/gson/Gson
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:909)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:838)
org.apache.jsp.outcome_jsp._jspService(outcome_jsp.java:178)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
com.web.servlet.ServerServlet.doPost(ServerServlet.java:60)
javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
根本原因
java.lang.NoClassDefFoundError：com/google/gson/Gson

根据调试器的信息，问题发生在以下行，因为找不到Gson包中的任何类：

  1. GsonBuilder gsonBuilder = new GsonBuilder();

有人可以帮助我解决这个java.lang.NoClassDefFoundError：com/google/gson/Gson问题吗？

英文:

I imported Gson through maven whose code is

  1. &lt;?xml version=&quot;1.0&quot; encoding=&quot;UTF-8&quot;?&gt;
  2. &lt;project xmlns=&quot;http://maven.apache.org/POM/4.0.0&quot;
  3.          xmlns:xsi=&quot;http://www.w3.org/2001/XMLSchema-instance&quot;
  4.          xsi:schemaLocation=&quot;http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd&quot;&gt;
  5.     &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
  7.     &lt;groupId&gt;org.example&lt;/groupId&gt;
  8.     &lt;artifactId&gt;HerbTea&lt;/artifactId&gt;
  9.     &lt;version&gt;1.0-SNAPSHOT&lt;/version&gt;
  10.     &lt;!-- https://mvnrepository.com/artifact/com.google.code.gson/gson --&gt;
  11.     &lt;dependencies&gt;
  12.         &lt;dependency&gt;
  13.             &lt;groupId&gt;com.google.code.gson&lt;/groupId&gt;
  14.             &lt;artifactId&gt;gson&lt;/artifactId&gt;
  15.             &lt;version&gt;2.8.5&lt;/version&gt;
  16.         &lt;/dependency&gt;
  17.         &lt;!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter-api --&gt;
  18.         &lt;dependency&gt;
  19.             &lt;groupId&gt;org.junit.jupiter&lt;/groupId&gt;
  20.             &lt;artifactId&gt;junit-jupiter-api&lt;/artifactId&gt;
  21.             &lt;version&gt;5.4.0&lt;/version&gt;
  22.             &lt;scope&gt;test&lt;/scope&gt;
  23.         &lt;/dependency&gt;
  24.         &lt;dependency&gt;
  25.             &lt;groupId&gt;org.junit.jupiter&lt;/groupId&gt;
  26.             &lt;artifactId&gt;junit-jupiter-api&lt;/artifactId&gt;
  27.             &lt;version&gt;5.4.0&lt;/version&gt;
  28.             &lt;scope&gt;compile&lt;/scope&gt;
  29.         &lt;/dependency&gt;
  32.     &lt;/dependencies&gt;
  36. &lt;/project&gt;

However, when I run my program on JSP sevlet program, I receive

  1. java.lang.NoClassDefFoundError: com/google/gson/Gson

and I don't know why.

You can see the error report here

  1. HTTP Status 500 – Internal Server Error
  2. ________________________________________
  3. Type Exception Report
  4. Message An exception occurred processing [/outcome.jsp] at line [21]
  5. Description The server encountered an unexpected condition that prevented it from fulfilling the request.
  6. Exception
  7. org.apache.jasper.JasperException: An exception occurred processing [/outcome.jsp] at line [21]
  9. 18:     &lt;% WindowDisplay windowDisplay = (WindowDisplay) request.getSession().getAttribute(&quot;windowDisplay&quot;);
  10. 19:         System.out.println(session.getAttribute(reqSymptomParamKey));
  11. 20:         windowDisplay.getRecipeDisplay();
  12. 21:         List&lt;Recipe&gt; a = windowDisplay.getRecipeDisplay().retrieveCorrespondingRecipe((List&lt;String&gt;) session.getAttribute(reqSymptomParamKey));
  13. 22:         for (Recipe i : windowDisplay.getRecipeDisplay().retrieveCorrespondingRecipe((List&lt;String&gt;) session.getAttribute(reqSymptomParamKey))) {%&gt;
  14. 23:     &lt;p1&gt;name:&lt;%=i.getName()%&gt; &lt;/p1&gt;
  15. 24:     &lt;p1&gt;Corresponding Symptom: &lt;%=i.getSymptomNameList()%&gt;&lt;/p1&gt;
  18. Stacktrace:
  19. 	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:617)
  20. 	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:499)
  21. 	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
  22. 	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
  23. 	javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
  24. 	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  25. 	com.web.servlet.ServerServlet.doPost(ServerServlet.java:60)
  26. 	javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
  27. 	javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
  28. 	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  29. Root Cause
  30. javax.servlet.ServletException: java.lang.NoClassDefFoundError: com/google/gson/Gson
  31. 	org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:909)
  32. 	org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:838)
  33. 	org.apache.jsp.outcome_jsp._jspService(outcome_jsp.java:178)
  34. 	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
  35. 	javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
  36. 	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476)
  37. 	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
  38. 	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
  39. 	javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
  40. 	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  41. 	com.web.servlet.ServerServlet.doPost(ServerServlet.java:60)
  42. 	javax.servlet.http.HttpServlet.service(HttpServlet.java:652)
  43. 	javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
  44. 	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
  45. Root Cause
  46. java.lang.NoClassDefFoundError: com/google/gson/Gson

The line where the problem occurs according to debugger is this one because any class in Gson package is not found:

  1. GsonBuilder gsonBuilder = new GsonBuilder();

Can somebody help me to get over this java.lang.NoClassDefFoundError: com/google/gson/Gson problem?

答案1

得分: 0

我最终自己找到了问题的答案。感谢那些帮助我编辑问题的人。

问题是我没有将Maven库添加到构件中。

解决方法是进入Intellij中的项目结构->构件->输出布局，然后在“可用元素”面板下点击相应的Maven导入的jar，将Gson库的jar添加到构件中。

英文:

I found out the question answer myself eventually. Thanks for those helping me in editing the question.

The problem is that I didn't add the Maven libaray into the artifact.

The solution will be going into Project Structure->Artifacts->Output layout in Intellij and click on the corresponding Maven imported jar under the "Available Elements" panel to add that Gson libaray jar into the artifact.

huangapple
  • 本文由 发表于 2020年7月30日 22:38:13
  • 转载请务必保留本文链接：https://go.coder-hub.com/63175516.html
  • gson
  • java
  • json
  • jsp
  • maven
匿名

发表评论

匿名网友

:?: :razz: :sad: :evil: :!: :smile: :oops: :grin: :eek: :shock: :???: :cool: :lol: :mad: :twisted: :roll: :wink: :idea: :arrow: :neutral: :cry: :mrgreen:

确定