javac编译文件和jar，但是java失败 [英] javac compiles files and jars but java fails

问题描述

我已将.java文件放在一个文件夹中，例如主文件夹内lib文件夹中的/opt/program/和.jar文件，例如/opt/program/lib/jsoup-1.10.3.jar.然后我运行这些命令

I have put the .java files in a folder, e.g. /opt/program/ and a .jar file in a lib folder inside the main folder, e.g. /opt/program/lib/jsoup-1.10.3.jar. Then I ran these commands

javac -classpath lib/*jar *.java      # compile is OK
java TheFrame                         # program runs

在其中一个Java文件中，例如Tester.java，我使用了jsoup-1.10.3.jar中定义的对象.像这样

In one of the java files, e.g. Tester.java, I have used an object defined in jsoup-1.10.3.jar. Something like this

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
public class Tester  {
   Document doc;
   public Tester()  { }
   public void doConnect(String name) throws Exception
   {
      doc = Jsoup.connect("http://somewhere.com").get();
      ...
   }
}

在运行时，当涉及到Jsoup.connect时，出现此错误

During the runtime, when it comes to Jsoup.connect, I get this error

java.lang.NoClassDefFoundError

更新:

根据建议，我还必须在Java命令中包含jar文件.我这样做了，但仍然收到相同的错误

As suggested, I have to include the jar file in the java command as well. I did that but still get the same error

$ ls lib/
jsoup-1.10.3.jar
$ /opt/jdk1.8.0_131/bin/javac -classpath lib/*.jar *.java
$ /opt/jdk1.8.0_131/bin/java -classpath .:lib/*.jar TheFrame
phase_1
java.util.concurrent.ExecutionException: java.lang.NoClassDefFoundError: org/jsoup/Jsoup
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    at javax.swing.SwingWorker.get(SwingWorker.java:602)
    at TheFrame$10.propertyChange(TheFrame.java:481)
    at java.beans.PropertyChangeSupport.fire(PropertyChangeSupport.java:335)
    ....
Caused by: java.lang.NoClassDefFoundError: org/jsoup/Jsoup
    at Tester.connectForTranscript(Tester.java:24)
    at ExcelFile.analyzeSeq(ExcelFile.java:706)
    at TheFrame$9.doInBackground(TheFrame.java:448)
    ....
Caused by: java.lang.ClassNotFoundException: org.jsoup.Jsoup
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    ....
Caused by: java.lang.NoClassDefFoundError: org/jsoup/Jsoup
    at Tester.doConnect(Tester.java:24)
    ...
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.ClassNotFoundException: org.jsoup.Jsoup
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 10 more

我该如何解决?

推荐答案

您使用设置了classpath的类来编译您的类:

You compile your class with the classpath set :

javac -classpath lib/*jar *.java 

但是您不会在设置了classpath的情况下启动可运行类:

but you don't launch the runnable class with the classpath set :

java TheFrame

此外，在.和扩展名.jar. "rel =" nofollow noreferrer>设置类路径文档以设置带有通配符的类路径.

Besides, the . and the extension .jar is not specified in the Setting the class path documentation to set a classpath with a wildcard.

类路径条目可以包含基本名称通配符， 这被认为等效于指定所有文件的列表 在扩展名为.jar或.JAR的目录中.例如， 类路径条目foo/指定目录中的所有JAR文件 foo. 仅由*组成的类路径条目扩展为所有列表 当前目录中的jar文件.

Class path entries can contain the basename wildcard character , which is considered equivalent to specifying a list of all the files in the directory with the extension .jar or .JAR. For example, the class path entry foo/ specifies all JAR files in the directory named foo. A classpath entry consisting simply of * expands to a list of all the jar files in the current directory.

包含*的类路径条目将与类文件不匹配.到 在单个目录foo中匹配类和JAR文件，请使用 foo; foo/*或foo/*; foo.选择的顺序确定是否 在foo中的JAR文件之前先加载foo中的类和资源，或者 反之亦然.

A class path entry that contains * will not match class files. To match both classes and JAR files in a single directory foo, use either foo;foo/* or foo/*;foo. The order chosen determines whether the classes and resources in foo are loaded before JAR files in foo, or vice versa.

子目录不是递归搜索的.例如，foo/*看起来 仅适用于foo中的JAR文件，而不能用于foo/bar，foo/baz等中.

Subdirectories are not searched recursively. For example, foo/* looks for JAR files only in foo, not in foo/bar, foo/baz, etc.

如果您的所有jar都位于lib文件夹的根目录下，这应该可以解决您的问题:

This should solve your problem if all your jar are located at the root of the lib folder:

java -classpath .:lib/*  TheFrame  

要编译您的类，应使用相同的synthax设置类路径.
令人惊讶的是，执行时没有编译错误:

To compile your class, you should use the same synthax to set the classpath.
It is surprising that you have no compilation error when you execute :

 javac -classpath lib/*jar *.java 

我尝试过:

javac -cp D:\repo\commons-lang3\3.1\*jar MyClass.java

我收到javac错误:

javac:无效标志: D:\ repo \ commons-lang3 \ 3.1 \ commons-lang3-3.1-sources.jar

javac: invalid flag: D:\repo\commons-lang3\3.1\commons-lang3-3.1-sources.jar

使用

javac -cp D:\repo\commons-lang3\3.1\* MyClass.java

编译很好.

与java命令的行为完全相同.

I have exactly the same behavior with the java command.

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