文章目录
- 1. pom
- 2. MemoryController
- 3. User 对象
- 4. 动态生成class文件工具类
- 5. 启动项目
- 6. 测试连接
- 7. 异常信息
1. pom
<!--动态生成class文件--><dependency><groupId>asm</groupId><artifactId>asm</artifactId><version>3.3.1</version></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-devtools</artifactId><scope>runtime</scope><optional>true</optional></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency>
2. MemoryController
package com.gblfy.chapter2;import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;import java.util.ArrayList;
import java.util.List;
import java.util.UUID;@RestController
public class MemoryController {private List<User> userList = new ArrayList<User>();private List<Class<?>> classList = new ArrayList<Class<?>>();/*** 构造堆内存溢出* 最大内存: -Xmx32M* 最小内存: -Xms32M* -Xmx32M -Xms32M*/@RequestMapping("/heap")public void heap() {int i = 0;while (true) {userList.add(new User(i++, UUID.randomUUID().toString()));}}/*** 构造非堆内存溢出* 最大Metaspace: -XX:MaxMetaspaceSize=32M* 最小Metaspace: -XX:MetaspaceSize=32M* -XX:MetaspaceSize=32M -XX:MaxMetaspaceSize=32M*/@RequestMapping("/noheap")public void noheap() {while (true) {classList.addAll(Metaspace.createClasses());}}
}3. User 对象
package com.gblfy.chapter2;import lombok.AllArgsConstructor;
import lombok.Data;@Data
@AllArgsConstructor
public class User {private int id;private String name;
}4. 动态生成class文件工具类
package com.gblfy.chapter2;import java.util.ArrayList;
import java.util.List;import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;/**https://blog.csdn.net/bolg_hero/article/details/78189621* 继承ClassLoader是为了方便调用defineClass方法，因为该方法的定义为protected* */
public class Metaspace extends ClassLoader {public static List<Class<?>> createClasses() {// 类持有List<Class<?>> classes = new ArrayList<Class<?>>();// 循环1000w次生成1000w个不同的类。for (int i = 0; i < 10000000; ++i) {ClassWriter cw = new ClassWriter(0);// 定义一个类名称为Class{i}，它的访问域为public，父类为java.lang.Object，不实现任何接口cw.visit(Opcodes.V1_1, Opcodes.ACC_PUBLIC, "Class" + i, null,"java/lang/Object", null);// 定义构造函数<init>方法MethodVisitor mw = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>","()V", null, null);// 第一个指令为加载thismw.visitVarInsn(Opcodes.ALOAD, 0);// 第二个指令为调用父类Object的构造函数mw.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object","<init>", "()V");// 第三条指令为returnmw.visitInsn(Opcodes.RETURN);mw.visitMaxs(1, 1);mw.visitEnd();Metaspace test = new Metaspace();byte[] code = cw.toByteArray();// 定义类Class<?> exampleClass = test.defineClass("Class" + i, code, 0, code.length);classes.add(exampleClass);}return classes;}
}
5. 启动项目
为了方便快速模拟，需要设置堆内存参数
6. 测试连接
测试堆内存溢出链接：
http://localhost/heap测试非堆内存溢出链接：
http://localhost/noheap
7. 异常信息
