调用“java -jar MyFile.jar"带有额外的类路径选项 [英] Call "java -jar MyFile.jar" with additional classpath option

问题描述

我创建了一个包含我所有编译内容的 jar 文件.此外，我的 ant 构建脚本将所需的库复制到子文件夹libs"中.结构如下:

I created a jar file containing all my compiled stuff. Additionally my ant build script copies the required libs into a subfolder "libs". The structure looks like this:

MyProgram.jar
libs/

所以当我现在尝试运行我的程序时，我收到以下错误:

So when I try to run my program now I get the following error:

java -cp ".:/home/user/java/MyProgram/jar/libs" -jar MyProgram.jar
java.lang.ClassNotFoundException: org.postgresql.Driver
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:186)
    at database.PostgresQL.getConnection(PostgresQL.java:38)
    at recommender.dao.Creative2IdxDAO.createCreatives2Idx(Creative2IdxDAO.java:19)
    at main.Main.calculateCorrelationMatrix(Main.java:51)
    at main.Main.main(Main.java:28)
java.lang.NullPointerException
    at recommender.dao.Creative2IdxDAO.createCreatives2Idx(Creative2IdxDAO.java:25)
    at main.Main.calculateCorrelationMatrix(Main.java:51)
    at main.Main.main(Main.java:28)

为什么会发生这种情况?

Why does this happen?

推荐答案

你使用 either -jar or -cp，你不能将两者结合起来.如果您想在类路径上放置额外的 JAR，那么您应该将它们放在主 JAR 的清单中，然后使用 java -jar 或者将完整的类路径(包括主 JAR 及其依赖项)放入-cp 并在命令行中明确命名主类

You use either -jar or -cp, you can't combine the two. If you want to put additional JARs on the classpath then you should either put them in the main JAR's manifest and then use java -jar or you put the full classpath (including the main JAR and its dependencies) in -cp and name the main class explicitly on the command line

java -cp 'MyProgram.jar:libs/*' main.Main

(我使用 dir/* 语法告诉 java 命令将所有 .jar 文件从特定目录添加到类路径.请注意，* 必须防止被 shell 扩展，这就是我使用单引号的原因.)

(I'm using the dir/* syntax that tells the java command to add all .jar files from a particular directory to the classpath. Note that the * must be protected from expansion by the shell, which is why I've used single quotes.)

您提到您正在使用 Ant，因此对于替代清单方法，您可以使用 ant 的 <manifestclasspath> 任务 after 复制依赖项但之前 构建 JAR.

You mention that you're using Ant so for the alternative manifest approach, you can use ant's <manifestclasspath> task after copying the dependencies but before building the JAR.

<manifestclasspath property="myprogram.manifest.classpath" jarfile="MyProgram.jar">
  <classpath>
    <fileset dir="libs" includes="*.jar" />
  </classpath>
</manifestclasspath>

<jar destfile="MyProgram.jar" basedir="classes">
  <manifest>
    <attribute name="Main-Class" value="main.Main" />
    <attribute name="Class-Path" value="${myprogram.manifest.classpath}" />
  </manifest>
</jar>

有了这个，java -jar MyProgram.jar 将正常工作，并且还将在类路径中包含所有 libs JAR 文件.

With this in place, java -jar MyProgram.jar will work correctly, and will include all the libs JAR files on the classpath as well.

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