JVM 修改类加载器启动类加载器

1、类加载器加载路径

public class MyTest18 {

    public static void main(String[] args) {
        //系统类加载器加载路径
        System.out.println(System.getProperty("sun.boot.class.path"));
        System.out.println();
        //扩展类加载器加载路径
        System.out.println(System.getProperty("java.ext.dirs"));
        System.out.println();
        //应用类加载器加载路径
        System.out.println(System.getProperty("java.class.path"));


    }
}

　　

返回结果

C:Program FilesJavajdk1.8.0_131jrelib
esources.jar;C:Program FilesJavajdk1.8.0_131jrelib
t.jar;C:Program FilesJavajdk1.8.0_131jrelibsunrsasign.jar;C:Program FilesJavajdk1.8.0_131jrelibjsse.jar;C:Program FilesJavajdk1.8.0_131jrelibjce.jar;C:Program FilesJavajdk1.8.0_131jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_131jrelibjfr.jar;C:Program FilesJavajdk1.8.0_131jreclasses

C:Program FilesJavajdk1.8.0_131jrelibext;C:WindowsSunJavalibext

C:Program FilesJavajdk1.8.0_131jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_131jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_131jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_131jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_131jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_131jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_131jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_131jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_131jrelibext
ashorn.jar;C:Program FilesJavajdk1.8.0_131jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_131jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_131jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_131jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_131jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_131jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_131jrelibjce.jar;C:Program FilesJavajdk1.8.0_131jrelibjfr.jar;C:Program FilesJavajdk1.8.0_131jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_131jrelibjsse.jar;C:Program FilesJavajdk1.8.0_131jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_131jrelibplugin.jar;C:Program FilesJavajdk1.8.0_131jrelib
esources.jar;C:Program FilesJavajdk1.8.0_131jrelib
t.jar;D:workspacestudy jvm_demouildclassesjavamain;D:Program FilesJetBrainsIntelliJ IDEA 2017.1.4libidea_rt.jar

　　将打印结果变成多行数据

C:Program FilesJavajdk1.8.0_131jrelib
esources.jar;
C:Program FilesJavajdk1.8.0_131jrelib
t.jar;
C:Program FilesJavajdk1.8.0_131jrelibsunrsasign.jar;
C:Program FilesJavajdk1.8.0_131jrelibjsse.jar;
C:Program FilesJavajdk1.8.0_131jrelibjce.jar;
C:Program FilesJavajdk1.8.0_131jrelibcharsets.jar;
C:Program FilesJavajdk1.8.0_131jrelibjfr.jar;
C:Program FilesJavajdk1.8.0_131jreclasses

C:Program FilesJavajdk1.8.0_131jrelibext;C:WindowsSunJavalibext

C:Program FilesJavajdk1.8.0_131jrelibcharsets.jar;
C:Program FilesJavajdk1.8.0_131jrelibdeploy.jar;
C:Program FilesJavajdk1.8.0_131jrelibextaccess-bridge-64.jar;
C:Program FilesJavajdk1.8.0_131jrelibextcldrdata.jar;
C:Program FilesJavajdk1.8.0_131jrelibextdnsns.jar;
C:Program FilesJavajdk1.8.0_131jrelibextjaccess.jar;
C:Program FilesJavajdk1.8.0_131jrelibextjfxrt.jar;
C:Program FilesJavajdk1.8.0_131jrelibextlocaledata.jar;
C:Program FilesJavajdk1.8.0_131jrelibext
ashorn.jar;
C:Program FilesJavajdk1.8.0_131jrelibextsunec.jar;
C:Program FilesJavajdk1.8.0_131jrelibextsunjce_provider.jar;
C:Program FilesJavajdk1.8.0_131jrelibextsunmscapi.jar;
C:Program FilesJavajdk1.8.0_131jrelibextsunpkcs11.jar;
C:Program FilesJavajdk1.8.0_131jrelibextzipfs.jar;
C:Program FilesJavajdk1.8.0_131jrelibjavaws.jar;
C:Program FilesJavajdk1.8.0_131jrelibjce.jar;
C:Program FilesJavajdk1.8.0_131jrelibjfr.jar;
C:Program FilesJavajdk1.8.0_131jrelibjfxswt.jar;
C:Program FilesJavajdk1.8.0_131jrelibjsse.jar;
C:Program FilesJavajdk1.8.0_131jrelibmanagement-agent.jar;
C:Program FilesJavajdk1.8.0_131jrelibplugin.jar;
C:Program FilesJavajdk1.8.0_131jrelib
esources.jar;
C:Program FilesJavajdk1.8.0_131jrelib
t.jar;
D:workspacestudy jvm_demouildclassesjavamain;
D:Program FilesJetBrainsIntelliJ IDEA 2017.1.4libidea_rt.jar

　　

2、修改类加载器启动类加载器

现在想把自己生成的类交给启动类加载器，那要怎么做呢？

主需要把生成的class文件放到根加载器的加载路径下 C:Program FilesJavajdk1.8.0_131jreclasses

创建测试类

public class MyTest18_1 {

    public static void main(String[] args) throws  Exception {
        MyTest16 loader1 = new MyTest16("loader1");
        loader1.setPath("D:/temp/");
        Class<?> clazz = loader1.loadClass("com.example.jvm.classloader.MyTest1");

        System.out.println("class: " +clazz.hashCode());
        System.out.println("class loader: " + clazz.getClassLoader());

    }
}

　　

运行结果如下：

class: 356573597
class loader: null

　　说明是启动加载器加载的MyTest1