JVM04-JVM内存泄露的场景以及排查

/**
 * Java堆内存异常
 VM Args:
 //这两个参数保证了堆中的可分配内存固定为20M
 -Xms20m
 -Xmx20m

 -XX:+HeapDumpOnOutOfMemoryError //自动生成dump文件
 //文件生成的位置，作为生成在桌面的一个目录
 -XX:HeapDumpPath=D:\srv\dump
 *
 * @author xiang.wei
 * @date 2020/5/27 13:35
 */
public class HeapOOM {
    /**
     * 创建一个内部类用于创建对象使用
     */
    static class OOMObject {
    }

    public static void main(String[] args) {
        List<OOMObject> list = new ArrayList<>();
        //无限的创建对象放在堆中
        while (true) {
            list.add(new OOMObject());
        }
    }
}

 -Xms20M -Xmx20M -Xmn20M   -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=D:\srv\dump

java.lang.OutOfMemoryError: Java heap space
Dumping heap to D:\srv\dump\java_pid23624.hprof ...
Heap dump file created [28062091 bytes in 0.143 secs]
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at com.jay.service.HeapOOM.main(HeapOOM.java:31)
Java HotSpot(TM) 64-Bit Server VM warning: MaxNewSize (20480k) is equal to or greater than the entire heap (20480k).  A new max generation size of 19968k will be used.

/**
 * VM Args:
 *    设置栈容量为160K，默认1M
 *    -Xss160k
 * @author xiang.wei
 * @date 2020/5/27 16:09
 */
public class JavaVMStackSOF {

    private int stackLength = 1;

    public void stackLeak() {
        stackLength++;
        System.out.println("*********栈的深度是:" + stackLength);
        //递归调用
        stackLeak();
    }

    public static void main(String[] args) throws Throwable {
        JavaVMStackSOF oom = new JavaVMStackSOF();
        try {
            oom.stackLeak();
        } catch (Exception e) {
            throw e;
        }
    }
}

*********栈的深度是:1287
Exception in thread "main" java.lang.StackOverflowError
    at sun.nio.cs.UTF_8.updatePositions(UTF_8.java:77)

/**
 * 在JDK8下测试方法区，所以设置了Metaspace的大小为固定的8M
 -XX:MetaspaceSize=8m
 -XX:MaxMetaspaceSize=8m
 * @author xiang.wei
 * @date 2020/5/27 17:29
 */
public class JavaMethodAreaOOM {
    public static void main(String[] args) {
        while (true) {
            Enhancer enhancer = new Enhancer();
            enhancer.setSuperclass(JOOMObject.class);
            enhancer.setUseCache(false);
            enhancer.setCallback((MethodInterceptor) (obj, method, objects, methodProxy) -> methodProxy.invokeSuper(obj,objects));
            //无限创建动态代理，生成class对象
            enhancer.create();
        }
    }
    static class JOOMObject{}

Exception in thread "main" java.lang.OutOfMemoryError: Metaspace
    at org.springframework.cglib.core.ReflectUtils.defineClass(ReflectUtils.java:538)
    at org.springframework.cglib.core.AbstractClassGenerator.generate(AbstractClassGenerator.java:363)