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tl;dr：如何将javax.activation.DataSource依赖项添加到通过 App Engine Maven 插件运行的服务器？

我正在使用App Engine Maven 插件部署到本地 App Engine 服务器，并且正在尝试使用 Blobstore API 上传文件。我正在使用 Java 11。

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>io.happycoding</groupId>
  <artifactId>blobstore-test</artifactId>
  <version>1</version>
  <packaging>war</packaging>

  <properties>
    <!-- App Engine currently supports Java 8 -->
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <failOnMissingWebXml>false</failOnMissingWebXml>
  </properties>

  <dependencies>
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>4.0.1</version>
      <scope>provided</scope>
    </dependency>

    <dependency>
      <groupId>org.apache.taglibs</groupId>
      <artifactId>taglibs-standard-spec</artifactId>
      <version>1.2.5</version>
    </dependency>

    <dependency>
      <groupId>com.google.appengine</groupId>
      <artifactId>appengine-api-1.0-sdk</artifactId>
      <version>1.9.59</version>
    </dependency>

  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>com.google.appengine</groupId>
        <artifactId>appengine-maven-plugin</artifactId>
        <version>1.9.71</version>
      </plugin>
    </plugins>
  </build>
</project>

索引.jsp

<%@ page import="com.google.appengine.api.blobstore.BlobstoreServiceFactory" %>

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
  </head>
  <body>

    <form action="<%= BlobstoreServiceFactory.getBlobstoreService().createUploadUrl("/submit") %>" 
      method="POST"
      enctype="multipart/form-data">

      Enter some text:
      <br/>
      <textarea name="text"></textarea>
      <br/>
      Select a file:
      <input type="file" name="image">
      <br/>
      <input type="submit" value="Submit">
    </form>

  </body>
</html>

提交Servlet.java

package io.happycoding.servlets;

import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/submit")
public class SubmitServlet extends HttpServlet {

  @Override
  public void doPost(HttpServletRequest request, HttpServletResponse response) {
    System.out.println("data submitted");
  }
}

运行本地服务器的命令： mvn appengine:devserver

我可以成功运行本地服务器，并且可以看到表单正确呈现，包括 Blobstore URL。

但是，当我提交表单时，我收到此错误：

java.lang.NoClassDefFoundError: javax/activation/DataSource
    at com.google.appengine.api.blobstore.dev.UploadBlobServlet.handleUpload(UploadBlobServlet.java:171)
    at com.google.appengine.api.blobstore.dev.UploadBlobServlet.access$000(UploadBlobServlet.java:69)
    at com.google.appengine.api.blobstore.dev.UploadBlobServlet$1.run(UploadBlobServlet.java:115)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at com.google.appengine.api.blobstore.dev.UploadBlobServlet.doPost(UploadBlobServlet.java:112)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:867)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1623)
    at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:134)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
    at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
    at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:63)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
    at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:48)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
    at com.google.appengine.tools.development.jetty9.StaticFileFilter.doFilter(StaticFileFilter.java:123)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectRequest(DevAppServerModulesFilter.java:366)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doDirectModuleRequest(DevAppServerModulesFilter.java:349)
    at com.google.appengine.tools.development.DevAppServerModulesFilter.doFilter(DevAppServerModulesFilter.java:116)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1610)
    at com.google.appengine.tools.development.DevAppServerRequestLogFilter.doFilter(DevAppServerRequestLogFilter.java:44)
    at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1602)
    at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:540)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:146)
    at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:257)
    at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1588)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:255)
    at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1345)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:203)
    at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:480)
    at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1557)
    at org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:201)
    at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1247)
    at com.google.appengine.tools.development.jetty9.DevAppEngineWebAppContext.doScope(DevAppEngineWebAppContext.java:94)
    at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:144)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at com.google.appengine.tools.development.jetty9.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:595)
    at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.eclipse.jetty.server.Server.handle(Server.java:502)
    at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:364)
    at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:260)
    at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:305)
    at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:103)
    at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:118)
    at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:333)
    at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:310)
    at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:168)
    at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:126)
    at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:366)
    at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:765)
    at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:683)
    at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.ClassNotFoundException: javax.activation.DataSource
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:471)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:588)
    at com.google.appengine.tools.development.DevAppServerClassLoader.loadClass(DevAppServerClassLoader.java:108)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
    ... 57 more

一些谷歌搜索揭示了很多关于这个问题的问题：

这些问题的答案建议添加这些依赖项的组合：

<dependency>
  <groupId>javax.activation</groupId>
  <artifactId>javax.activation-api</artifactId>
  <version>1.2.0</version>
</dependency>

<dependency>
    <groupId>javax.activation</groupId>
    <artifactId>activation</artifactId>
    <version>1.1.1</version>
</dependency>

<dependency>
    <groupId>com.sun.activation</groupId>
    <artifactId>javax.activation</artifactId>
    <version>1.2.0</version>
</dependency>

我已经尝试添加其中的每一个，并且尝试添加所有这些。但无论如何，我仍然收到上述错误。

我理解为什么会发生这种情况：Java 8 包含javax.activation.DataSource该类，但随后将其删除。因此，由于我使用的是 Java 11，因此缺少该类。但是到目前为止我尝试过的所有依赖项似乎都没有提供缺少的类，可能是因为我使用的是 App Engine Maven 插件而不是运行我自己的服务器？

如何将此依赖项添加到使用 App Engine Maven 插件的项目中？

4

3 回答 3

1

我会先尝试添加

<dependency>
    <groupId>javax.activation</groupId>
    <artifactId>activation</artifactId>
    <version>1.1.1</version>
</dependency>

正如您所指出的，但我的期望是您收到 NoClassDefFound 错误，因为 javax.activation 类没有被 Maven 添加到战争中。出于这个原因，我仍然主要使用 Ant 进行 jar/war/ear 构建：更冗长，但不那么神奇。如果您查看项目的 /target 文件夹，您应该能够看到 war 文件：如果您这样做，jar tf <warfile>您应该能够看到添加到 WEB-INF/lib 的所有 jar 文件，这将告诉您它是否正在添加激活罐。

查看https://github.com/GoogleCloudPlatform/appengine-maven-plugin，推荐的示例包括此插件：

<plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <version>2.3</version>
            <configuration>
                <archiveClasses>true</archiveClasses>
            </configuration>
        </plugin>

appengine-maven-plugin在你的 pom.build 部分的条目之前。我会把它放进去，然后看看它是否正确地建立了战争。

于 2019-04-02T14:52:12.220 回答
1

Google App Engine 不支持 Java 11。它只支持 Java 8。

于 2019-03-28T04:16:39.303 回答
0

我在本地环境中切换回 Java 8。在 AppEngine 上它可以工作。

于 2020-09-17T21:22:23.133 回答