一、介绍

java -cp 命令中 cp 指的就是 classpath。使用该命令可以运行jar中的某个指定的测试类

使用方法

Java -cp 依赖jar或者是依赖jar库 测试类的全限定名

1

其中需要注意的是“依赖jar或者是依赖库”一定要是绝对路径。如果依赖的是jar库，多个jar路径之间的分割符会因平台的不同存在差异，在window上用分号";“分割，在linux上用冒号”:"分割

二、使用

1、创建springboot功能

创建一个springboot项目，名叫javapc

新建MyTestBean类

package com.javapc.demo.test;

public class MyTestBean {

private String name;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public void outStr() {

System.out.println("我是猪！！！");

}

}

在resources下创建spring.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

       xsi:schemaLocation="http://www.springframework.org/schema/beans

       http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="myTestBean" class="com.javapc.demo.test.MyTestBean"/>

</beans>

创建测试类Test

package com.javapc.demo.test;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

public static void main(String[] args) {

ApplicationContext ac = new ClassPathXmlApplicationContext("spring.xml");

MyTestBean bean = (MyTestBean) ac.getBean("myTestBean");

bean.outStr();

}

}

项目结构很简单，如下图所示

2、项目打包并运行

1. 打包项目

   

   打包完成后我们通过java -pc 运行一下

   
   

   zhishengjie@zhishengjiedeMacBook-Pro target % java -cp demo-0.0.1-SNAPSHOT.jar com.javapc.demo.test.Test

   Error: A JNI error has occurred, please check your installation and try again

   Exception in thread "main" java.lang.NoClassDefFoundError: org/springframework/context/ApplicationContext

   at java.lang.Class.getDeclaredMethods0(Native Method)

   at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)

   at java.lang.Class.privateGetMethodRecursive(Class.java:3048)

   at java.lang.Class.getMethod0(Class.java:3018)

   at java.lang.Class.getMethod(Class.java:1784)

   at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:650)

   at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:632)

   Caused by: java.lang.ClassNotFoundException: org.springframework.context.ApplicationContext

   at java.net.URLClassLoader.findClass(URLClassLoader.java:382)

   at java.lang.ClassLoader.loadClass(ClassLoader.java:418)

   at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355)

   at java.lang.ClassLoader.loadClass(ClassLoader.java:351)

   ... 7 more

   我们会发现，起不来，会报java.lang.NoClassDefFoundError错误。其实我们一看就知道原因，是因为缺少spring的相关依赖。其实springboot项目打包需要借助一个plugin的，否则打出来的jar中是不会包含项目启动所需要的依赖的。但是我们要的就是不包含依赖jar的项目jar包

   
   

   <!-- springboot打包插件 -->

   <plugin>

       <groupId>org.springframework.boot</groupId>

       <artifactId>spring-boot-maven-plugin</artifactId>

       <configuration>

           <mainClass>com.javapc.demo.JavapcApplication</mainClass>

           <!-- <skip>true</skip> -->

       </configuration>

       <executions>

           <execution>

               <goals>

                   <goal>repackage</goal>

               </goals>

           </execution>

       </executions>

   </plugin>

   其实此刻我们发现的这个问题，也是 java -cp 的一个优点。

   举个例子：

   假如我们这个程序的运行时需要依赖另一个叫 other.jar 的包。

   如果我们使用 java -jar 的话，就只能把 other.jar 放到 demo-0.0.1-SNAPSHOT.jar 中，因为 -jar 后面只能指定一个 jar 包启动。

   如果使用 -cp ，我们可以选择将 other.jar 放到 demo-0.0.1-SNAPSHOT.jar 中，也可以选择不放入 demo-0.0.1-SNAPSHOT.jar 中，使用以下命令来运行：

   # 当前环境是linux，所以使用":"分割

   java -cp other.jar:demo-0.0.1-SNAPSHOT.jar com.javapc.demo.test.Test

   这样做的好处就是，假如修改了 demo-0.0.1-SNAPSHOT.jar 中的某个类，可以只上传修改后的 demo-0.0.1-SNAPSHOT.jar 到服务器，jar体积更小，上传也会节约很多时间。

   
   

   其实讲到这里大家就都已经清楚上面的报错应该怎么修改了，不就是jar中没有包含项目启动所需要的spring的相关jar嘛，我们把spring的jar拎出来放到单独的一个文件夹中，我们使用 java -cp 运行

   
   

   # java -cp 依赖jar:依赖jar:依赖jar:demo-0.0.1-SNAPSHOT.jar com.javapc.demo.test.Test

   java -cp spring1.jar:spring2.jar:spring3.jar:demo-0.0.1-SNAPSHOT.jar com.javapc.demo.test.Test

   是不是就是上面脚本这个意思，但是我们依赖的jar有很多，这样一个一个写进来岂不是要累死了，所以我们可以通过shell脚本来实现

   
   

   启动程序的shell脚本

   
   

   export LANG=en_US.UTE-8

   rootpath="/Users/zhishengjie/workspace/IdeaProjects/test_javapc"

   appname="project"

   apppath=${rootpath}/${appname}

   cd ${apppath}

   export CP_PATH=.

   # 加载启动项目所需的依赖jar，这里就是指项目所依赖的spring相关jar

   for i in `ls ${rootpath}/libs/`

   do

    CP_PATH=$CP_PATH:${rootpath}/libs/$i

   done

   echo "打印加载的依赖……"

   echo ${CP_PATH}

   echo "打印依赖结束！"

   # 加载项目jar，这里就是指demo-0.0.1-SNAPSHOT.jar

   for i in `ls ${apppath}/`

   do

    CP_PATH=$CP_PATH:${apppath}/$i

   done

   echo "打印部署jar的……"

   echo ${CP_PATH}

   echo "打印部署jar结束！"

   # com.javapc.demo.test.Test 指的就是项目中启动的测试类的全限定类名

   exec=`ps -ef |  grep com.javapc.demo.test.Test | grep java | grep -v grep | awk '{print $2}'`

   if [ -n "$exec"];then

      echo "Processing testbat is  running. Don't call it again. "

   fi

   if [ -z "$exec"];then

     echo "Start the process testbat."

     java -cp ${CP_PATH}  -Dfile.encoding=utf-8 -Xmx512m  -Xmx12288m com.javapc.demo.test.Test $*

   fi

   下图为存放的目录结构

   
   

   运行脚本，这不就成功了嘛

   
   

   zhishengjie@zhishengjiedeMacBook-Pro test_javapc % ./start.sh

   打印加载的依赖……

   .:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/jakarta.annotation-api-1.3.5.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/jul-to-slf4j-1.7.31.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/log4j-api-2.14.1.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/log4j-to-slf4j-2.14.1.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/logback-classic-1.2.3.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/logback-core-1.2.3.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/slf4j-api-1.7.31.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/snakeyaml-1.28.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-aop-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-beans-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-boot-2.5.2.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-boot-autoconfigure-2.5.2.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-boot-jarmode-layertools-2.5.2.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-context-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-core-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-expression-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-jcl-5.3.8.jar

   打印依赖结束！

   打印部署jar的……

   .:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/jakarta.annotation-api-1.3.5.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/jul-to-slf4j-1.7.31.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/log4j-api-2.14.1.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/log4j-to-slf4j-2.14.1.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/logback-classic-1.2.3.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/logback-core-1.2.3.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/slf4j-api-1.7.31.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/snakeyaml-1.28.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-aop-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-beans-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-boot-2.5.2.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-boot-autoconfigure-2.5.2.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-boot-jarmode-layertools-2.5.2.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-context-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-core-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-expression-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/libs/spring-jcl-5.3.8.jar:/Users/zhishengjie/workspace/IdeaProjects/test_javapc/project/demo.jar

   打印部署jar结束！

   Processing ecifbat is  running. Don't call it again. 

   Start the process ecifat.

   14:59:37.405 [main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5fcfe4b2

   14:59:37.548 [main] DEBUG org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loaded 1 bean definitions from class path resource [spring.xml]

   14:59:37.577 [main] DEBUG org.springframework.beans.factory.support.DefaultListableBeanFactory - Creating shared instance of singleton bean 'myTestBean'

   我是猪！！！

   zhishengjie@zhishengjiedeMacBook-Pro test_javapc % 

   
   

   其实本文到此就应该结束了，但是有的小伙伴可能会有些疑问，你怎么知道项目依赖的spring的jar都有哪些的？这……

   其实我是使用springboot的插件打了个jar，把这个jar包中的BOOT-INF下的lib目录给拿过来了……