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为什么客户端JAR 崩溃，java.lang.NoClassDefFoundError由 引起ClassNotFoundException，但run来自 gradle 工作正常？客户端如何使用库JAR 有问题吗？

thufir@mordor:~/NetBeansProjects/hello_client$ 
thufir@mordor:~/NetBeansProjects/hello_client$ gradle clean build
Starting a new Gradle Daemon for this build (subsequent builds will be faster).
Download https://jitpack.io/com/github/THUFIR/hello_api/dev/hello_api-dev.pom
Download https://repo1.maven.org/maven2/org/codehaus/groovy/groovy-all/2.4.1/groovy-all-2.4.1.pom
Download https://jitpack.io/com/github/THUFIR/hello_api/dev/hello_api-dev.jar
Download https://repo1.maven.org/maven2/org/codehaus/groovy/groovy-all/2.4.1/groovy-all-2.4.1.jar
Changed strategy of configuration ':compile' after it has been resolved. This behaviour has been deprecated and is scheduled to be removed in Gradle 3.0
:clean
:compileJava
:processResources UP-TO-DATE
:classes
:jar
:startScripts
:distTar
:distZip
:assemble
:compileTestJava UP-TO-DATE
:processTestResources UP-TO-DATE
:testClasses UP-TO-DATE
:test UP-TO-DATE
:check UP-TO-DATE
:build

BUILD SUCCESSFUL

Total time: 1 mins 11.959 secs
thufir@mordor:~/NetBeansProjects/hello_client$ 
thufir@mordor:~/NetBeansProjects/hello_client$ java -jar build/libs/hello_client.jar 
Exception in thread "main" java.lang.NoClassDefFoundError: net/bounceme/mordor/hello/library/HelloLibrary
    at net.bounceme.mordor.hello.client.Client.runLibrary(Client.java:13)
    at net.bounceme.mordor.hello.client.Client.main(Client.java:9)
Caused by: java.lang.ClassNotFoundException: net.bounceme.mordor.hello.library.HelloLibrary
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 2 more
thufir@mordor:~/NetBeansProjects/hello_client$ 
thufir@mordor:~/NetBeansProjects/hello_client$ gradle clean run
Changed strategy of configuration ':compile' after it has been resolved. This behaviour has been deprecated and is scheduled to be removed in Gradle 3.0
:clean
:compileJava
:processResources UP-TO-DATE
:classes
:run
hello [fred]

BUILD SUCCESSFUL

Total time: 4.66 secs
thufir@mordor:~/NetBeansProjects/hello_client$

正如它应该的那样，上面的输出是“hello [fred]”，这很好。hello world 客户端代码： 

package net.bounceme.mordor.hello.client;

import static java.lang.System.out;
import net.bounceme.mordor.hello.library.HelloLibrary;

public class Client {

    public static void main(String[] args) {
        new Client().runLibrary();
    }

    private void runLibrary() {
        HelloLibrary library = new HelloLibrary();
        out.println(library.hello("fred"));
    }

}

Netbeans 抱怨导入语句 for net.bounceme.mordor.hello.library.HelloLibrary，这似乎是正确的：

thufir@mordor:~$ 
thufir@mordor:~$ cp .gradle/caches/modules-2/files-2.1/com.github.THUFIR/hello_api/dev/fa670823cfe9548b87c75f224a48a1089eab0b35/hello_api-dev.jar jar
thufir@mordor:~$ 
thufir@mordor:~$ cd jar
thufir@mordor:~/jar$ 
thufir@mordor:~/jar$ jar -xf hello_api-dev.jar 
thufir@mordor:~/jar$ 
thufir@mordor:~/jar$ cat META-INF/MANIFEST.MF 
Manifest-Version: 1.0

thufir@mordor:~/jar$           
thufir@mordor:~/jar$ ll net/bounceme/mordor/hello/library/HelloLibrary.class 
-rw-rw-r-- 1 thufir thufir 728 Mar 11  2016 net/bounceme/mordor/hello/library/HelloLibrary.class
thufir@mordor:~/jar$

这是客户端 JAR：

thufir@mordor:~/NetBeansProjects/hello_client$              
thufir@mordor:~/NetBeansProjects/hello_client$ cd build/libs/
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ jar -xf hello_client.jar 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ cat META-INF/MANIFEST.MF 
Manifest-Version: 1.0
Main-Class: net.bounceme.mordor.hello.client.Client
Class-Path: hello_api-dev.jar groovy-all-2.4.1.jar

thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ ll net/bounceme/mordor/hello/client/Client.class 
-rw-rw-r-- 1 thufir thufir 912 Mar 11 02:28 net/bounceme/mordor/hello/client/Client.class
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$

在我看来，类路径包含hello_api-dev.jar正确。

这似乎值得注意：

在可能的情况下，避免以 compile fileTree(dir: 'lib', include: ['*.jar']) 的方式使用依赖项。基于 Maven 或 JCenter 等存储库的托管依赖项比随机目录中的依赖项更容易始终如一地使用。如果这些是您不想发布到开源工件存储库的内部库，那么可能值得设置一个本地 Nexus 实例或类似实例。

https://stackoverflow.com/a/35304025/262852

但是，我不太确定这是否是问题所在，因为我似乎使用了来自 jitpack 的正确 JAR 和正确包装。

我什至将库添加到libs客户端的文件夹中：

thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ jar -vft hello_client.jar 
     0 Fri Mar 11 02:50:28 PST 2016 META-INF/
   135 Fri Mar 11 02:50:28 PST 2016 META-INF/MANIFEST.MF
     0 Fri Mar 11 02:50:28 PST 2016 net/
     0 Fri Mar 11 02:50:28 PST 2016 net/bounceme/
     0 Fri Mar 11 02:50:28 PST 2016 net/bounceme/mordor/
     0 Fri Mar 11 02:50:28 PST 2016 net/bounceme/mordor/hello/
     0 Fri Mar 11 02:50:28 PST 2016 net/bounceme/mordor/hello/client/
   927 Fri Mar 11 02:50:28 PST 2016 net/bounceme/mordor/hello/client/HelloClient.class
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ jar -vft libs/hello_api-dev.jar 
     0 Fri Mar 11 01:59:38 PST 2016 META-INF/
    25 Fri Mar 11 01:59:38 PST 2016 META-INF/MANIFEST.MF
     0 Fri Mar 11 01:59:38 PST 2016 net/
     0 Fri Mar 11 01:59:38 PST 2016 net/bounceme/
     0 Fri Mar 11 01:59:38 PST 2016 net/bounceme/mordor/
     0 Fri Mar 11 01:59:38 PST 2016 net/bounceme/mordor/hello/
     0 Fri Mar 11 01:59:38 PST 2016 net/bounceme/mordor/hello/library/
   728 Fri Mar 11 01:59:38 PST 2016 net/bounceme/mordor/hello/library/HelloLibrary.class
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ java -jar hello_client.jar 
Exception in thread "main" java.lang.NoClassDefFoundError: net/bounceme/mordor/hello/library/HelloLibrary
    at net.bounceme.mordor.hello.client.HelloClient.runLibrary(HelloClient.java:13)
    at net.bounceme.mordor.hello.client.HelloClient.main(HelloClient.java:9)
Caused by: java.lang.ClassNotFoundException: net.bounceme.mordor.hello.library.HelloLibrary
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 2 more
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$

这就引出了一个问题： 为什么不 gradle 为客户复制库？

4

1 回答 1

1

杂牌：

thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ cp /home/thufir/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-all/2.4.1/a9ca9c9de09361ec2a18d2c058d2524fbd8eae0c/groovy-all-2.4.1.jar hello_api-dev.jar hello_client.jar .
cp: ‘hello_api-dev.jar’ and ‘./hello_api-dev.jar’ are the same file
cp: ‘hello_client.jar’ and ‘./hello_client.jar’ are the same file
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ jar -i hello_client.jar 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ ll
total 6816
drwxrwxr-x 2 thufir thufir    4096 Mar 11 03:41 ./
drwxrwxr-x 6 thufir thufir    4096 Mar 11 03:30 ../
-rw-rw-r-- 1 thufir thufir 6937913 Mar 11 03:41 groovy-all-2.4.1.jar
-rw-rw-r-- 1 thufir thufir    1422 Mar 11 03:39 hello_api-dev.jar
-rw-rw-r-- 1 thufir thufir    2722 Mar 11 03:41 hello_client.jar
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ 
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$ java -jar hello_client.jar 
hello [fred]
thufir@mordor:~/NetBeansProjects/hello_client/build/libs$

1.) 为什么这行得通？

2.) 构建这些 JAR 的正确方法是什么？

这必须是少数（如果不是唯一的话）阅读精美手册实际上有用的案例之一。我看到了“i”开关，它显示：

thufir@mordor:~/NetBeansProjects/hello_client$ 
thufir@mordor:~/NetBeansProjects/hello_client$ jar -i build/libs/hello_client.jar 
java.io.FileNotFoundException: build/libs/hello_api-dev.jar (No such file or directory)
    at java.util.zip.ZipFile.open(Native Method)
    at java.util.zip.ZipFile.<init>(ZipFile.java:219)
    at java.util.zip.ZipFile.<init>(ZipFile.java:149)
    at java.util.jar.JarFile.<init>(JarFile.java:166)
    at java.util.jar.JarFile.<init>(JarFile.java:103)
    at sun.tools.jar.Main.getJarPath(Main.java:1163)
    at sun.tools.jar.Main.getJarPath(Main.java:1179)
    at sun.tools.jar.Main.genIndex(Main.java:1195)
    at sun.tools.jar.Main.run(Main.java:317)
    at sun.tools.jar.Main.main(Main.java:1288)
thufir@mordor:~/NetBeansProjects/hello_client$

但是，我并不真正理解该输出，只是好奇这是一个“找不到文件”异常。

于 2016-03-11T11:42:55.337 回答