Jenkins插件無法訪問從站上的文件

Question

通過我自己的插件，我需要知道Jenkins從站的工作區中是否存在文件。但該文件無法找到，而它確實存在於從站（D:\workspace\JOB_NAME\test.txt）。

public class MyBuilder extends Builder implements Serializable { 

    private static final long serialVersionUID = 1L; 

    public boolean perform(AbstractBuild<?, ?> build, Launcher launcher, BuildListener listener) 
      throws InterruptedException, IOException { 

     FilePath fp = new FilePath(build.getWorkspace(), "test.txt"); 

     String result = fp.act(new FileCallable<String>() { 
      private static final long serialVersionUID = 1L; 

      @Override 
      public String invoke(File file, VirtualChannel channel) throws IOException, InterruptedException { 
       if (file.getAbsoluteFile().exists()){ 
        return file.getName() + " exists."; 
       } else { 
        return file.getName() + " doesn't exist."; 
       } 
      } 
     }); 

     System.out.println("result: " + result); 

結果：

FATAL: remote file operation failed: D:\workspace\JOB_NAME\test.txt at hudson.remoting.Channel@182752b:Slave 
hudson.util.IOException2: remote file operation failed: D:\workspace\JOB_NAME\test.txt at hudson.remoting.Channel@182752b:Slave 
    at hudson.FilePath.act(FilePath.java:900) 
    at hudson.FilePath.act(FilePath.java:877) 
    at com.company.tlb.proj.MyBuilder.perform(Unknown Source) 
    at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:19) 
    at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:804) 
    at hudson.model.Build$BuildExecution.build(Build.java:199) 
    at hudson.model.Build$BuildExecution.doRun(Build.java:160) 
    at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:586) 
    at hudson.model.Run.execute(Run.java:1575) 
    at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46) 
    at hudson.model.ResourceController.execute(ResourceController.java:88) 
    at hudson.model.Executor.run(Executor.java:237) 
Caused by: java.io.IOException: Unable to serialize hudson.FilePath$FileCallableWrapper@18b91cb 
    at hudson.remoting.UserRequest.serialize(UserRequest.java:166) 
    at hudson.remoting.UserRequest.<init>(UserRequest.java:62) 
    at hudson.remoting.Channel.call(Channel.java:671) 
    at hudson.FilePath.act(FilePath.java:893) 
    ... 11 more 
Caused by: java.io.NotSerializableException: java.io.PrintStream 
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1164) 
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1518) 
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1483) 
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400) 
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158) 
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1518) 
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1483) 
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400) 
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158) 
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1518) 
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1483) 
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1400) 
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1158) 
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:330) 
    at hudson.remoting.UserRequest._serialize(UserRequest.java:155) 
    at hudson.remoting.UserRequest.serialize(UserRequest.java:164) 
    ... 14 more 

我在做什麼錯？

鏈接：

• Making your plugin behave in distributed Jenkins
• Jenkins API: FilePath.java

Answer 1

你傳遞一個匿名內部類act(...)它有它的父類，MyBuilder的隱式引用。我的猜測是，儘管MyBuilder實現了Serializable，但由於某些參考不是Serializable（例如java.io.PrintStream，因爲堆棧跟蹤指示），所以它實際上不能被序列化。

讓您的FileCallable<String>一個靜態內部類的實例擺脫了隱式引用其父的：

private static class MyFileCallable implements FileCallable<String> { 
    private static final long serialVersionUID = 1L; 
    @Override 
    public String invoke(File file, VirtualChannel channel) throws IOException, InterruptedException { 
    if (file.getAbsoluteFile().exists()){ 
     return file.getName() + " exists."; 
    } else { 
     return file.getName() + " doesn't exist."; 
    } 
    } 
} 

，然後用它來代替：

String result = fp.act(new MyFileCallable()); 

更新： 這裏的一個鏈接到Java的Nested Classes教程，它概述了內部類的一個實例和它的封閉外部類實例之間的關係：

的將InnerClass實例只能在 在OuterClass的實例存在，並且具有到所述方法和它的 外圍實例的字段的直接訪問。

這也在JLS（§8.1.3 Inner Classes and Enclosing Instances）的更多技術術語中解釋。

考慮到這一點，從Serializable doc這句話解釋了爲什麼你遇到的NotSerializableException：

當遍歷一個圖形，對象可能會遇到不支持 Serializable接口。在這種情況下，將拋出NotSerializableException，並將標識不可序列化對象的類 。