Java 类自身正常编译，但通过 JSP 运行时抛出 NoClassFoundException 或 NoClassDefFoundError答案

【问题标题】：Java class compiles normally by itself, but throws NoClassFoundException or NoClassDefFoundError when run through a JSPJava 类自身正常编译，但通过 JSP 运行时抛出 NoClassFoundException 或 NoClassDefFoundError
【发布时间】：2018-05-30 02:50:11
【问题描述】：

我有一个 java 类，可以成功地将 Firebase 消息发送到我的 android 手机。我正在尝试从 JSP 文件运行该类，但它会导致 NoClassFoundException 和 NoClassDefFoundError。这是 JSP 文件：

<%@ page import="send.Notify" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    Api token is: <%
        out.print(request.getParameter("token"));
    %>
<%

Notify.SendMessage(request.getParameter("token"),"title","body");
%>
</body>
</html>

需要说明的是，当 Notify.SendMessage 被注释掉时，我确实从 out.print 得到了正常的输出，所以问题不在于输入。

这是我的课：

package send;

import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.auth.oauth2.GoogleCredentials;
import com.google.firebase.FirebaseApp;
import com.google.firebase.FirebaseOptions;
import com.google.firebase.messaging.FirebaseMessaging;
import com.google.firebase.messaging.Message;
import com.google.firebase.messaging.Notification
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Arrays;

public class Notify {
public static void main(String[] args) throws Exception{

    SendMessage("f7ne...",
            "title", "body");
}

public static void SendMessage(String registrationToken, String title, String body) throws Exception{
    FileInputStream serviceAccount =
            new FileInputStream("C:\\Users\\michael\\IdeaProjects\\servlet 3\\web\\notification-32ebc-firebase-adminsdk-5lbs4-643271e91a.json");

    FirebaseOptions options = new FirebaseOptions.Builder()
            .setCredentials(GoogleCredentials.fromStream(serviceAccount))
            .setDatabaseUrl("https://notification-32ebc.firebaseio.com")
            .build();

    FirebaseApp.initializeApp(options);

    Notification notification = new Notification(title, body);
    Message message = Message.builder()
            .setToken(registrationToken)
            .setNotification(notification)
            .build();


    String response = FirebaseMessaging.getInstance().send(message);
    System.out.println(response);
}
private static String getAccessToken() throws IOException {
    GoogleCredential googleCredential = GoogleCredential
            .fromStream(new FileInputStream("C:\\Users\\michael\\IdeaProjects\\servlet 3\\web\\notification-32ebc-firebase-adminsdk-5lbs4-643271e91a.json"))
            .createScoped(Arrays.asList("https://www.googleapis.com/auth/firebase.messaging",
                    "https://www.googleapis.com/auth/firebase.database",
                    "https://www.googleapis.com/auth/userinfo.email",
                    "https://www.googleapis.com/auth/firebase"));
    googleCredential.refreshToken();
    return googleCredential.getAccessToken();
}

}

这里是错误：

Type Exception Report

Message An exception occurred processing [/notification.jsp] at line [15]

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

org.apache.jasper.JasperException: An exception occurred processing [/notification.jsp] at line [15]

12:         /*Notify.SendMessage("f7neXi6q4KQ:APA91bFI3acBwgtDq99_D2duax_qY1zAMGCE62yHQ5CsL-UhyJdvAs97CUhzXzY0q7tyWKX2JM0WlyvZtL-arTW9s1useO816ujda5c4gYKM-I_uCN8m81EH9clwNeVG6kQzGU-zl93k",
13:                 "jsp title", "jsp body");*/
14:         try{
15:             Notify.SendMessage(request.getParameter("token"),"title","body");
16:         }catch (Exception e){
17:             out.print("error!");
18:         }


Stacktrace:
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:593)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:467)
    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:741)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Root Cause

javax.servlet.ServletException: java.lang.NoClassDefFoundError: com/google/firebase/FirebaseOptions$Builder
    org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:667)
    org.apache.jsp.notification_jsp._jspService(notification_jsp.java:154)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:444)
    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:741)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Root Cause

java.lang.NoClassDefFoundError: com/google/firebase/FirebaseOptions$Builder
    send.Notify.SendMessage(Notify.java:26)
    org.apache.jsp.notification_jsp._jspService(notification_jsp.java:135)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:444)
    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:741)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Root Cause

java.lang.ClassNotFoundException: com.google.firebase.FirebaseOptions$Builder
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1292)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1121)
    send.Notify.SendMessage(Notify.java:26)
    org.apache.jsp.notification_jsp._jspService(notification_jsp.java:135)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:444)
    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:741)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Note The full stack trace of the root cause is available in the server logs.

这是我的文件夹结构： https://prnt.sc/jocl6h

【问题讨论】：

标签： java android firebase jsp tomcat

【解决方案1】：

类路径中缺少firebase-core jar。 firebase 的文档包含 gradle 的说明。

dependencies { implementation 'com.google.firebase:firebase-core:16.0.1' }

如果您使用的是 maven，请使用适当的 maven 声明替换依赖项

<dependency> <groupId>com.google.firebase</groupId> <artifactId>firebase-core</artifactId> <version>16.0.1</version> </dependency>

【讨论】：

【解决方案2】：

问题是 Intellij 不使用您添加到项目中的依赖项也到 tomcat 服务器。为了解决这个问题，我手动将我的 maven 文件夹 (C:\Users\user.m2) 中的所有 jar 添加到 project/web/WEB-INF/lib 文件夹中。

这是一个解决方案，但我仍在寻找正确的方法。

更新：我最近尝试重构我的程序。在 IntelliJ 中，从 apache webapp 原型创建一个新的 maven 项目。然后你可以添加你所有的依赖和类，Tomcat会成功找到它们。

【讨论】：