JVM启动过程 类加载器
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下图来自：http://blog.csdn.net/jiangwei0910410003/article/details/17733153
package com.test.jvm.common; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; /** * 自定义的类加载器 */ public class MyClassLoader extends ClassLoader { private String name; //加载器的名字 // private String className; //被加载类的全名 private String path = "D:/workspace/eclipse-workspace64bit17-forPersonalProject/openbank-parent/openbank-test/src/test/java/"; //加载类的路径 private final String fileType = ".class"; //class文件的扩展名 public MyClassLoader(String name) { super(); //让系统类加载器成为该类加载器的父类 this.name = name; } public MyClassLoader(ClassLoader parent,String name) { super(parent); //显示指定该类加载器的的父加载器 this.name = name; } @Override public String toString() { // TODO Auto-generated method stub return this.name; } // TODO Auto-generated method stub private byte[] loadClassData(String className) { InputStream inputStream = null; byte[] data = null; ByteArrayOutputStream byteArrayOutputStream = null; try { className = className.replace(‘.‘, ‘/‘); inputStream = new FileInputStream(new File(path+className+fileType)); byteArrayOutputStream = new ByteArrayOutputStream(); int ch = 0; while(-1 != (ch = inputStream.read())) { byteArrayOutputStream.write(ch); } data = byteArrayOutputStream.toByteArray(); } catch (Exception e) { e.printStackTrace(); } finally { try { inputStream.close(); byteArrayOutputStream.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return data; } @Override protected Class<?> findClass(String className) throws ClassNotFoundException { byte[] data =this.loadClassData(className); //将字节数组转换成Class对象 return this.defineClass(className, data, 0, data.length); } public String getPath() { return path; } public void setPath(String path) { this.path = path; } public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException { System.out.println(System.getProperty("java.class.path")); System.out.println("------------------"); MyClassLoader loader1 = new MyClassLoader("loader1"); // loader1.setPath("D:/temp/serverlib"); MyClassLoader loader2 = new MyClassLoader(loader1,"loader2"); //将loader1作为loader2的父加载器 // loader2.setPath("D:/temp/clientlib"); MyClassLoader loader3 = new MyClassLoader(null,"loader3"); //将第一个参数设为空表示父加载器为根加载器 // loader3.setPath("d:/temp/systemlib"); test(loader2); System.out.println("-----------------"); test(loader3); } public static void test(ClassLoader loader) throws ClassNotFoundException, InstantiationException, IllegalAccessException { Class clazz = loader.loadClass("com.test.jvm.common.Sample"); Object object = clazz.newInstance(); } }
public class Sample { public int v1 = 1; public Sample() { System.out.println("Sample is loaded by: "+this.getClass().getClassLoader()); new Dog(); } }
public class Dog { public Dog() { System.out.println("Dog is loaded by: "+this.getClass().getClassLoader()); } }
我将编译后的Sample.class和Dog.class放在他们源代码所在的包里
运行结果：
D:\\workspace\\eclipse-workspace64bit17-forPersonalProject\\openbank-parent\\openbank-test\\target\\test-classes;D:\\workspace\\eclipse-workspace64bit17-forPersonalProject\\openbank-parent\\openbank-test\\target\\classes;D:\\IDE\\eclipse\\plugins\\org.testng.eclipse_6.9.13.201609291640\\lib\\testng.jar;D:\\IDE\\eclipse\\plugins\\org.testng.eclipse_6.9.13.201609291640\\lib\\jcommander.jar;D:\\IDE\\eclipse\\plugins\\org.testng.eclipse_6.9.13.201609291640\\lib\\bsh-2.0b4.jar;D:\\IDE\\eclipse\\plugins\\org.testng.eclipse_6.9.13.201609291640\\lib\\snakeyaml.jar;D:\\workspace\\eclipse-workspace64bit17-forPersonalProject\\openbank-parent\\openbank-batch\\target\\classes;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\batch\\spring-batch-core\\3.0.6.RELEASE\\spring-batch-core-3.0.6.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\com\\ibm\\jbatch\\com.ibm.jbatch-tck-spi\\1.0\\com.ibm.jbatch-tck-spi-1.0.jar;C:\\Users\\Ash\\.m2\\repository\\javax\\batch\\javax.batch-api\\1.0\\javax.batch-api-1.0.jar;C:\\Users\\Ash\\.m2\\repository\\com\\thoughtworks\\xstream\\xstream\\1.4.7\\xstream-1.4.7.jar;C:\\Users\\Ash\\.m2\\repository\\xmlpull\\xmlpull\\1.1.3.1\\xmlpull-1.1.3.1.jar;C:\\Users\\Ash\\.m2\\repository\\xpp3\\xpp3_min\\1.1.4c\\xpp3_min-1.1.4c.jar;C:\\Users\\Ash\\.m2\\repository\\org\\codehaus\\jettison\\jettison\\1.2\\jettison-1.2.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\batch\\spring-batch-infrastructure\\3.0.6.RELEASE\\spring-batch-infrastructure-3.0.6.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\retry\\spring-retry\\1.1.0.RELEASE\\spring-retry-1.1.0.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-beans\\4.1.9.RELEASE\\spring-beans-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-context\\4.1.9.RELEASE\\spring-context-4.1.9.RELEASE.jar;D:\\workspace\\eclipse-workspace64bit17-forPersonalProject\\openbank-parent\\openbank-base\\target\\classes;C:\\Users\\Ash\\.m2\\repository\\commons-dbcp\\commons-dbcp\\1.4\\commons-dbcp-1.4.jar;C:\\Users\\Ash\\.m2\\repository\\commons-pool\\commons-pool\\1.6\\commons-pool-1.6.jar;C:\\Users\\Ash\\.m2\\repository\\com\\oracle\\ojdbc6\\11.2.0.4\\ojdbc6-11.2.0.4.jar;C:\\Users\\Ash\\.m2\\repository\\junit\\junit\\3.8.1\\junit-3.8.1.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\boot\\spring-boot-starter-web\\1.2.8.RELEASE\\spring-boot-starter-web-1.2.8.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\boot\\spring-boot-starter\\1.2.8.RELEASE\\spring-boot-starter-1.2.8.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\boot\\spring-boot\\1.2.8.RELEASE\\spring-boot-1.2.8.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\boot\\spring-boot-autoconfigure\\1.2.8.RELEASE\\spring-boot-autoconfigure-1.2.8.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\boot\\spring-boot-starter-logging\\1.2.8.RELEASE\\spring-boot-starter-logging-1.2.8.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\slf4j\\jul-to-slf4j\\1.7.13\\jul-to-slf4j-1.7.13.jar;C:\\Users\\Ash\\.m2\\repository\\org\\slf4j\\log4j-over-slf4j\\1.7.13\\log4j-over-slf4j-1.7.13.jar;C:\\Users\\Ash\\.m2\\repository\\ch\\qos\\logback\\logback-classic\\1.1.3\\logback-classic-1.1.3.jar;C:\\Users\\Ash\\.m2\\repository\\ch\\qos\\logback\\logback-core\\1.1.3\\logback-core-1.1.3.jar;C:\\Users\\Ash\\.m2\\repository\\org\\yaml\\snakeyaml\\1.14\\snakeyaml-1.14.jar;C:\\Users\\Ash\\.m2\\repository\\com\\fasterxml\\jackson\\core\\jackson-databind\\2.4.6\\jackson-databind-2.4.6.jar;C:\\Users\\Ash\\.m2\\repository\\com\\fasterxml\\jackson\\core\\jackson-annotations\\2.4.6\\jackson-annotations-2.4.6.jar;C:\\Users\\Ash\\.m2\\repository\\com\\fasterxml\\jackson\\core\\jackson-core\\2.4.6\\jackson-core-2.4.6.jar;C:\\Users\\Ash\\.m2\\repository\\org\\hibernate\\hibernate-validator\\5.1.3.Final\\hibernate-validator-5.1.3.Final.jar;C:\\Users\\Ash\\.m2\\repository\\javax\\validation\\validation-api\\1.1.0.Final\\validation-api-1.1.0.Final.jar;C:\\Users\\Ash\\.m2\\repository\\org\\jboss\\logging\\jboss-logging\\3.1.3.GA\\jboss-logging-3.1.3.GA.jar;C:\\Users\\Ash\\.m2\\repository\\com\\fasterxml\\classmate\\1.0.0\\classmate-1.0.0.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-core\\4.1.9.RELEASE\\spring-core-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-web\\4.1.9.RELEASE\\spring-web-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-webmvc\\4.1.9.RELEASE\\spring-webmvc-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-expression\\4.1.9.RELEASE\\spring-expression-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\boot\\spring-boot-starter-batch\\1.2.8.RELEASE\\spring-boot-starter-batch-1.2.8.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\hsqldb\\hsqldb\\2.3.3\\hsqldb-2.3.3.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-jdbc\\4.1.9.RELEASE\\spring-jdbc-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\boot\\spring-boot-starter-jetty\\1.2.8.RELEASE\\spring-boot-starter-jetty-1.2.8.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-jsp\\9.2.14.v20151106\\jetty-jsp-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\toolchain\\jetty-schemas\\3.1.M0\\jetty-schemas-3.1.M0.jar;C:\\Users\\Ash\\.m2\\repository\\javax\\servlet\\javax.servlet-api\\3.1.0\\javax.servlet-api-3.1.0.jar;C:\\Users\\Ash\\.m2\\repository\\javax\\servlet\\jsp\\javax.servlet.jsp-api\\2.3.1\\javax.servlet.jsp-api-2.3.1.jar;C:\\Users\\Ash\\.m2\\repository\\org\\glassfish\\web\\javax.servlet.jsp\\2.3.2\\javax.servlet.jsp-2.3.2.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\orbit\\javax.servlet.jsp.jstl\\1.2.0.v201105211821\\javax.servlet.jsp.jstl-1.2.0.v201105211821.jar;C:\\Users\\Ash\\.m2\\repository\\org\\glassfish\\web\\javax.servlet.jsp.jstl\\1.2.2\\javax.servlet.jsp.jstl-1.2.2.jar;C:\\Users\\Ash\\.m2\\repository\\org\\glassfish\\javax.el\\3.0.0\\javax.el-3.0.0.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\orbit\\org.eclipse.jdt.core\\3.8.2.v20130121\\org.eclipse.jdt.core-3.8.2.v20130121.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-webapp\\9.2.14.v20151106\\jetty-webapp-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-xml\\9.2.14.v20151106\\jetty-xml-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-util\\9.2.14.v20151106\\jetty-util-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-servlet\\9.2.14.v20151106\\jetty-servlet-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-security\\9.2.14.v20151106\\jetty-security-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-server\\9.2.14.v20151106\\jetty-server-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\websocket\\websocket-server\\9.2.14.v20151106\\websocket-server-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\websocket\\websocket-common\\9.2.14.v20151106\\websocket-common-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\websocket\\websocket-api\\9.2.14.v20151106\\websocket-api-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-io\\9.2.14.v20151106\\jetty-io-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\websocket\\websocket-client\\9.2.14.v20151106\\websocket-client-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\websocket\\websocket-servlet\\9.2.14.v20151106\\websocket-servlet-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-http\\9.2.14.v20151106\\jetty-http-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\websocket\\javax-websocket-server-impl\\9.2.14.v20151106\\javax-websocket-server-impl-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-annotations\\9.2.14.v20151106\\jetty-annotations-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-plus\\9.2.14.v20151106\\jetty-plus-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\jetty-jndi\\9.2.14.v20151106\\jetty-jndi-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\javax\\annotation\\javax.annotation-api\\1.2\\javax.annotation-api-1.2.jar;C:\\Users\\Ash\\.m2\\repository\\org\\ow2\\asm\\asm\\5.0.1\\asm-5.0.1.jar;C:\\Users\\Ash\\.m2\\repository\\org\\ow2\\asm\\asm-commons\\5.0.1\\asm-commons-5.0.1.jar;C:\\Users\\Ash\\.m2\\repository\\org\\ow2\\asm\\asm-tree\\5.0.1\\asm-tree-5.0.1.jar;C:\\Users\\Ash\\.m2\\repository\\org\\eclipse\\jetty\\websocket\\javax-websocket-client-impl\\9.2.14.v20151106\\javax-websocket-client-impl-9.2.14.v20151106.jar;C:\\Users\\Ash\\.m2\\repository\\javax\\websocket\\javax.websocket-api\\1.0\\javax.websocket-api-1.0.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\data\\spring-data-redis\\1.7.0.RELEASE\\spring-data-redis-1.7.0.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\data\\spring-data-keyvalue\\1.1.0.RELEASE\\spring-data-keyvalue-1.1.0.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\data\\spring-data-commons\\1.9.4.RELEASE\\spring-data-commons-1.9.4.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-tx\\4.1.9.RELEASE\\spring-tx-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-oxm\\4.1.9.RELEASE\\spring-oxm-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-aop\\4.1.9.RELEASE\\spring-aop-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\aopalliance\\aopalliance\\1.0\\aopalliance-1.0.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-context-support\\4.1.9.RELEASE\\spring-context-support-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\slf4j\\slf4j-api\\1.7.19\\slf4j-api-1.7.19.jar;C:\\Users\\Ash\\.m2\\repository\\org\\slf4j\\jcl-over-slf4j\\1.7.13\\jcl-over-slf4j-1.7.13.jar;C:\\Users\\Ash\\.m2\\repository\\redis\\clients\\jedis\\2.8.0\\jedis-2.8.0.jar;C:\\Users\\Ash\\.m2\\repository\\org\\apache\\commons\\commons-pool2\\2.2\\commons-pool2-2.2.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\boot\\spring-boot-starter-test\\1.2.8.RELEASE\\spring-boot-starter-test-1.2.8.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\mockito\\mockito-core\\1.10.19\\mockito-core-1.10.19.jar;C:\\Users\\Ash\\.m2\\repository\\org\\objenesis\\objenesis\\2.1\\objenesis-2.1.jar;C:\\Users\\Ash\\.m2\\repository\\org\\hamcrest\\hamcrest-core\\1.3\\hamcrest-core-1.3.jar;C:\\Users\\Ash\\.m2\\repository\\org\\hamcrest\\hamcrest-library\\1.3\\hamcrest-library-1.3.jar;C:\\Users\\Ash\\.m2\\repository\\org\\springframework\\spring-test\\4.1.9.RELEASE\\spring-test-4.1.9.RELEASE.jar;C:\\Users\\Ash\\.m2\\repository\\org\\testng\\testng\\6.9.10\\testng-6.9.10.jar;C:\\Users\\Ash\\.m2\\repository\\com\\beust\\jcommander\\1.48\\jcommander-1.48.jar;C:\\Users\\Ash\\.m2\\repository\\org\\beanshell\\bsh\\2.0b4\\bsh-2.0b4.jar ------------------ Sample is loaded by: [email protected] Dog is loaded by: [email protected] ----------------- Sample is loaded by: loader3 Dog is loaded by: loader3
如果我将Sample.class和Dog.class放在非System.getProperty("java.class.path")路径下，则AppClassLoader将无法找到这个类，则加载这个类的任务将落在自定义类加载器身上，那么上面的输出结果将会不同
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