如何制作自己公司网站,网站制作文章,新开传奇网站,赣榆哪里有做网站的目录
一、javac编译
1. 编译过程
2. 语法糖
二、Class文件
1. 文件格式
2. 常量池项目
3. 属性类型
三、Class文件实例
1. 源代码
2. javap分析Class文件
四、字节码指令
五、参考资料 一、javac编译
1. 编译过程 javac命令由Java语言编写#xff0c;目的将Ja…目录
一、javac编译
1. 编译过程
2. 语法糖
二、Class文件
1. 文件格式
2. 常量池项目
3. 属性类型
三、Class文件实例
1. 源代码
2. javap分析Class文件
四、字节码指令
五、参考资料 一、javac编译
1. 编译过程 javac命令由Java语言编写目的将Java源码转变成字节码只完成源码到抽象语法树或字节码的生成JDK12源码其运行入口是com.sun.tools.javac.Main#main。javac主体代码如下图所示。com.sun.tools.javac.main.JavaCompiler#compile核心方法。 javac编译过程一个准备初始化插入式注解处理器三个处理解析与填充符号表、处理注解处理器、语义分析与字节码生成如下图所示。 需要注意的是生成init()、clinit()方法在编译期完成Lombok操作通过插入式注解处理器完成对字段的getter()和setter()方法。
2. 语法糖 二、Class文件
1. 文件格式 Class文件是字节为单位的二进制流有两种数据类型无符号数、表如下图所示。Class文件不保存方法、字段最终的内存布局信息JVM运行期才能找到内存入口地址。 Class文件格式如下表所示主要有常量池、字段表、方法表、属性表等。Class文件可以使用十六进制编辑器WinHex打开。注意常量池constant_pool的数量是constant_pool_count减1若为0说明“不引用任何常量池项目”而其他表从0开始计数。 数据类型 名称 数量 作用及特点 u4 magic 1 1.魔数确定文件是否是Class文件 2.固定值0xCAFEBABE。 u2 minnor_version 1 次版本号 u2 major_version 1 1.主版本号 2.JDK向前兼容老版本则不能向后兼容新版本。 u2 constant_pool_count 1 1.常量池容量计数数量 2.索引从1开始其他表从0开始 3.若为0则说明“不引用任何常量池项目”。 cp_info constant_pool constant_pool_count - 1 1.常量池有两大类常量字面量、符号引用 2.有17种不同类型常量如 CONSTANT_Utf8_info、 CONSTANT_Class_info、 CONSTANT_Fieldref_info、 CONSTANT_Methodref_info、...... u2 access_flags 1 1.类或接口的访问修饰符 2.如ACC_PUBLIC是否为public修饰。 u2 this_class 1 类索引当前类的全限定名 u2 super_class 1 1.父类索引当前类的父类的全限定名 2.除java.lang.Object外所有类的父类值都不为0。 u2 interfaces_count 1 1.接口索引的数量 2.没有实现任何接口时该值为0。 u2 interfaces interfaces_count 1.接口索引当前类的所有接口的全限定名 2.接口从左往右的顺序在该表中。 u2 fields_count 1 类或接口的字段数量 field_info fields fields_count 1.类或接口的字段实例变量类变量 2.不包括方法内局部变量 3.内容有修饰符、在常量池中索引、简单名称、描述符、属性表attribute_info; 4.“描述符”字段的数据类型、方法的参数列表及返回值 5.不会列出父类或接口的字段 6.可能含有JVM自动生成的字段如this字段。 u2 methods_count 1 类或接口的方法数量 method_info methods methods_count 1.类或接口的方法实例方法类方法 2.内容有修饰符、在常量池中索引、简单名称、描述符、属性表attribute_info的Code; 3.“描述符”字段的数据类型、方法的参数列表及返回值 4.不会列出父类或接口的方法重写除外 5.可能含有JVM自动生成的方法如init()、cinit()方法。 u2 attributes_count 1 属性表数量 attribute_info attributes attributes_count 1.Class文件、字段、方法都有自己的属性 2.属性只要不重名任何编译器都可以添加自己的属性信息。
2. 常量池项目 常量池有两大类常量字面量、符号引用。当类加载时从常量池获得对应的符号引用再在类创建或运行解析时翻译到具体的内存地址中。如下表所示是17种不同类型的常量。 “描述符”作用是描述字段的数据类型、方法的参数列表包括数量、类型、顺序、返回值。数组类型每一个维度用前置的“[”标识如void inc(int[ ] ints)其描述符为([I)V。下表所示是描述符标识字符含义。 3. 属性类型 Class文件、字段、方法都有自己的属性这些属性存储到属性表attribute_info《Java虚拟机规范》允许属性只要不重名任何编译器都可以添加自己的属性信息。 如下表所示是常用属性介绍其中整个Class文件中只有Code属性描述方法体的代码其他所有数据项目都是描述元数据。 常用属性 使用位置 含义 Code 方法表 1.作用描述方法体代码注意不是所有方法都有Code属性如接口、抽象类的方法等 2.Code属性表中常用参数 max_stack操作数栈的最大深度 max_locals局部变量表的最大slot数量不是空间大小 args_size方法的参数数量注意若实例方法则有this参数 code方法体的字节码指令流 ..... LineNumberTable Code属性 1.源码行号与字节码指令行的对应关系 2.字节码指令的“行”是相对于方法体开始的偏移量。 LocalVariableTable Code属性 1.方法的局部变量描述 2.注意若实例方法则有this参数 3.结构中start_pc变量开始的字节码偏移量 length长度决定变量的作用域。 StackMapTable Code属性 1.目的类加载时字节码验证阶段进行类型检查新类型检查器 2.含义0或多个栈映射帧代表字节码偏移量即执行到该字节码时局部变量表和操作数栈的验证类型。 ConstantValue 字段表 1.常量值为static修饰的变量赋值的值 2.常量值只能是基本数据类型、String。 Exceptions 方法表 方法抛出的异常列表 InnerClasses 类文件 内部类列表 Signature 类、方法表、 字段表 1.记录泛型签名信息如类型变量、类型参数等 2.反射API就是根据这个属性来获取泛型信息。 MethodParameters 方法表 记录方法的各个形参和信息 Synthetic 类、方法表、 字段表 1.标识方法或字段是编译器自动生成至少有Synthetic或ACC_SYNTHETIC一个; 2.如实例构造器init()、类构造器cinit(); 其他Deprecated(含有Deprecated)、EnclosingMethod含有局部类或匿名类、 RuntimeVisibleAnnotations运行时可见的注解反射可调用、SourceFile记录源文件名称、 RuntimeInvisibleAnnotations运行时不可见的注解反射不可调用、 AnnotationDefault含有注解类元素默认值、Modlue记录模块信息、 BootstrapMethods保存invokedynamic指令引用的引导方法限定符、 ......
三、Class文件实例
1. 源代码 如下代码用javac编译成Class文件。
package com.common.instance.demo.core.serviceLevel;import com.alibaba.fastjson.JSON;
import com.log.util.LogUtil;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.stereotype.Component;import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.*;/*** description 一级业务线程池处理业务* author tcm* version 1.0.0* date 2021/9/29 16:01**/
Component
public class OneLevelAsyncContext implements InitializingBean {private final String URI uri;private final String PARAMS params;private AsyncListener asyncListener;private LinkedBlockingDequeRunnable queue;private ThreadPoolExecutor executor;public Object submitFuture(final HttpServletRequest request, final CallableObject task) throws ExecutionException, InterruptedException {// 获取请求URIfinal String uri request.getRequestURI();// 获取请求参数final MapString, String[] params request.getParameterMap();// 开启异步上下文final AsyncContext asyncContext request.startAsync();asyncContext.getRequest().setAttribute(URI, uri);asyncContext.getRequest().setAttribute(PARAMS, params);// 超时设置asyncContext.setTimeout(2 * 1000);if (Objects.nonNull(asyncListener)) {asyncContext.addListener(this.asyncListener);}// 线程池处理业务FutureObject future executor.submit(new CallableObject() {Overridepublic Object call() throws Exception {// 业务处理Object result task.call();return result;}});// 完成异步上下文否则报超时等异常asyncContext.complete();return future.get();}// 完成初始化配置Overridepublic void afterPropertiesSet() throws Exception {// 线程池大小int corePoolSize Integer.parseInt(100);// 最大线程池大小int maxNumPoolSize Integer.parseInt(200);// 任务队列queue new LinkedBlockingDequeRunnable();// 创建线程池executor new ThreadPoolExecutor(corePoolSize, maxNumPoolSize, 100, TimeUnit.MILLISECONDS, queue);executor.allowCoreThreadTimeOut(true);// 线程池饱和处理executor.setRejectedExecutionHandler(new RejectedExecutionHandler() {Overridepublic void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {if (r instanceof CanceledCallable) {CanceledCallable cc ((CanceledCallable) r);AsyncContext asyncContext cc.asyncContext;try {ServletRequest request asyncContext.getRequest();String uri (String) request.getAttribute(URI);Map params (Map) request.getAttribute(PARAMS);LogUtil.error(String.format(async request %s, uri:%s, params:%s, rejectedExecution, uri, JSON.toJSONString(params)));} catch (Exception ex) {}try {HttpServletResponse response (HttpServletResponse) asyncContext.getResponse();response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);} finally {asyncContext.complete();}}}});// 创建监听器if (Objects.isNull(asyncListener)) {asyncListener new AsyncListener() {Overridepublic void onComplete(AsyncEvent asyncEvent) throws IOException {}Overridepublic void onTimeout(AsyncEvent asyncEvent) throws IOException {AsyncContext asyncContext asyncEvent.getAsyncContext();try {ServletRequest request asyncContext.getRequest();String uri (String) request.getAttribute(URI);Map params (Map) request.getAttribute(PARAMS);LogUtil.error(String.format(async request timeout, uri:%s, params:%s, uri, JSON.toJSONString(params)));} catch (Exception e) {}try {HttpServletResponse resp (HttpServletResponse) asyncContext.getResponse();resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);} finally {asyncContext.complete();}}Overridepublic void onError(AsyncEvent asyncEvent) throws IOException {AsyncContext asyncContext asyncEvent.getAsyncContext();try {ServletRequest request asyncContext.getRequest();String uri (String) request.getAttribute(URI);Map params (Map) request.getAttribute(PARAMS);LogUtil.error(String.format(async request error, uri:%s, params:%s, uri, JSON.toJSONString(params)));} catch (Exception e) {}try {HttpServletResponse resp (HttpServletResponse) asyncContext.getResponse();resp.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);} finally {asyncContext.complete();}}Overridepublic void onStartAsync(AsyncEvent asyncEvent) throws IOException {}};}}}2. javap分析Class文件 javap命令分析Class文件如javap -verbose OneLevelAsyncContext.class代码所示。
Classfile /E:/Idea Project/instance-demo/target/classes/com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext.classLast modified 2023-7-22; size 4120 bytesMD5 checksum ab1d73e3259040031896505e9ed1e1bbCompiled from OneLevelAsyncContext.java
public class com.common.instance.demo.core.serviceLevel.OneLevelAsyncContext implements org.springframework.beans.factory.InitializingBeanminor version: 0major version: 52flags: ACC_PUBLIC, ACC_SUPER
Constant pool:#1 Methodref #42.#99 // java/lang/Object.init:()V#2 String #70 // uri#3 Fieldref #10.#100 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext.URI:Ljava/lang/String;#4 String #71 // params#5 Fieldref #10.#101 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext.PARAMS:Ljava/lang/String;#6 InterfaceMethodref #102.#103 // javax/servlet/http/HttpServletRequest.getRequestURI:()Ljava/lang/String;#7 InterfaceMethodref #102.#104 // javax/servlet/http/HttpServletRequest.getParameterMap:()Ljava/util/Map;#8 InterfaceMethodref #102.#105 // javax/servlet/http/HttpServletRequest.startAsync:()Ljavax/servlet/AsyncContext;#9 InterfaceMethodref #106.#107 // javax/servlet/AsyncContext.getRequest:()Ljavax/servlet/ServletRequest;#10 Class #108 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext#11 InterfaceMethodref #109.#110 // javax/servlet/ServletRequest.setAttribute:(Ljava/lang/String;Ljava/lang/Object;)V#12 Long 2000l#14 InterfaceMethodref #106.#111 // javax/servlet/AsyncContext.setTimeout:(J)V#15 Fieldref #10.#112 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext.asyncListener:Ljavax/servlet/AsyncListener;#16 Methodref #113.#114 // java/util/Objects.nonNull:(Ljava/lang/Object;)Z#17 InterfaceMethodref #106.#115 // javax/servlet/AsyncContext.addListener:(Ljavax/servlet/AsyncListener;)V#18 Fieldref #10.#116 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext.executor:Ljava/util/concurrent/ThreadPoolExecutor;#19 Class #117 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$1#20 Methodref #19.#118 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$1.init:(Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;Ljava/util/concurrent/Callable;)V#21 Methodref #30.#119 // java/util/concurrent/ThreadPoolExecutor.submit:(Ljava/util/concurrent/Callable;)Ljava/util/concurrent/Future;#22 InterfaceMethodref #106.#120 // javax/servlet/AsyncContext.complete:()V#23 InterfaceMethodref #121.#122 // java/util/concurrent/Future.get:()Ljava/lang/Object;#24 String #123 // 100#25 Methodref #124.#125 // java/lang/Integer.parseInt:(Ljava/lang/String;)I#26 String #126 // 200#27 Class #127 // java/util/concurrent/LinkedBlockingDeque#28 Methodref #27.#99 // java/util/concurrent/LinkedBlockingDeque.init:()V#29 Fieldref #10.#128 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext.queue:Ljava/util/concurrent/LinkedBlockingDeque;#30 Class #129 // java/util/concurrent/ThreadPoolExecutor#31 Long 100l#33 Fieldref #130.#131 // java/util/concurrent/TimeUnit.MILLISECONDS:Ljava/util/concurrent/TimeUnit;#34 Methodref #30.#132 // java/util/concurrent/ThreadPoolExecutor.init:(IIJLjava/util/concurrent/TimeUnit;Ljava/util/concurrent/BlockingQueue;)V#35 Methodref #30.#133 // java/util/concurrent/ThreadPoolExecutor.allowCoreThreadTimeOut:(Z)V#36 Class #134 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$2#37 Methodref #36.#135 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$2.init:(Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;)V#38 Methodref #30.#136 // java/util/concurrent/ThreadPoolExecutor.setRejectedExecutionHandler:(Ljava/util/concurrent/RejectedExecutionHandler;)V#39 Methodref #113.#137 // java/util/Objects.isNull:(Ljava/lang/Object;)Z#40 Class #138 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$3#41 Methodref #40.#135 // com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$3.init:(Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;)V#42 Class #139 // java/lang/Object#43 Class #140 // org/springframework/beans/factory/InitializingBean#44 Utf8 InnerClasses#45 Utf8 URI#46 Utf8 Ljava/lang/String;#47 Utf8 ConstantValue#48 Utf8 PARAMS#49 Utf8 asyncListener#50 Utf8 Ljavax/servlet/AsyncListener;#51 Utf8 queue#52 Utf8 Ljava/util/concurrent/LinkedBlockingDeque;#53 Utf8 Signature#54 Utf8 Ljava/util/concurrent/LinkedBlockingDequeLjava/lang/Runnable;;#55 Utf8 executor#56 Utf8 Ljava/util/concurrent/ThreadPoolExecutor;#57 Utf8 init#58 Utf8 ()V#59 Utf8 Code#60 Utf8 LineNumberTable#61 Utf8 LocalVariableTable#62 Utf8 this#63 Utf8 Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;#64 Utf8 submitFuture#65 Utf8 (Ljavax/servlet/http/HttpServletRequest;Ljava/util/concurrent/Callable;)Ljava/lang/Object;#66 Utf8 request#67 Utf8 Ljavax/servlet/http/HttpServletRequest;#68 Utf8 task#69 Utf8 Ljava/util/concurrent/Callable;#70 Utf8 uri#71 Utf8 params#72 Utf8 Ljava/util/Map;#73 Utf8 asyncContext#74 Utf8 Ljavax/servlet/AsyncContext;#75 Utf8 future#76 Utf8 Ljava/util/concurrent/Future;#77 Utf8 LocalVariableTypeTable#78 Utf8 Ljava/util/concurrent/CallableLjava/lang/Object;;#79 Utf8 Ljava/util/MapLjava/lang/String;[Ljava/lang/String;;#80 Utf8 Ljava/util/concurrent/FutureLjava/lang/Object;;#81 Utf8 StackMapTable#82 Class #141 // java/lang/String#83 Class #142 // java/util/Map#84 Class #143 // javax/servlet/AsyncContext#85 Utf8 Exceptions#86 Class #144 // java/util/concurrent/ExecutionException#87 Class #145 // java/lang/InterruptedException#88 Utf8 MethodParameters#89 Utf8 (Ljavax/servlet/http/HttpServletRequest;Ljava/util/concurrent/CallableLjava/lang/Object;;)Ljava/lang/Object;#90 Utf8 afterPropertiesSet#91 Utf8 corePoolSize#92 Utf8 I#93 Utf8 maxNumPoolSize#94 Class #146 // java/lang/Exception#95 Utf8 SourceFile#96 Utf8 OneLevelAsyncContext.java#97 Utf8 RuntimeVisibleAnnotations#98 Utf8 Lorg/springframework/stereotype/Component;#99 NameAndType #57:#58 // init:()V#100 NameAndType #45:#46 // URI:Ljava/lang/String;#101 NameAndType #48:#46 // PARAMS:Ljava/lang/String;#102 Class #147 // javax/servlet/http/HttpServletRequest#103 NameAndType #148:#149 // getRequestURI:()Ljava/lang/String;#104 NameAndType #150:#151 // getParameterMap:()Ljava/util/Map;#105 NameAndType #152:#153 // startAsync:()Ljavax/servlet/AsyncContext;#106 Class #143 // javax/servlet/AsyncContext#107 NameAndType #154:#155 // getRequest:()Ljavax/servlet/ServletRequest;#108 Utf8 com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext#109 Class #156 // javax/servlet/ServletRequest#110 NameAndType #157:#158 // setAttribute:(Ljava/lang/String;Ljava/lang/Object;)V#111 NameAndType #159:#160 // setTimeout:(J)V#112 NameAndType #49:#50 // asyncListener:Ljavax/servlet/AsyncListener;#113 Class #161 // java/util/Objects#114 NameAndType #162:#163 // nonNull:(Ljava/lang/Object;)Z#115 NameAndType #164:#165 // addListener:(Ljavax/servlet/AsyncListener;)V#116 NameAndType #55:#56 // executor:Ljava/util/concurrent/ThreadPoolExecutor;#117 Utf8 com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$1#118 NameAndType #57:#166 // init:(Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;Ljava/util/concurrent/Callable;)V#119 NameAndType #167:#168 // submit:(Ljava/util/concurrent/Callable;)Ljava/util/concurrent/Future;#120 NameAndType #169:#58 // complete:()V#121 Class #170 // java/util/concurrent/Future#122 NameAndType #171:#172 // get:()Ljava/lang/Object;#123 Utf8 100#124 Class #173 // java/lang/Integer#125 NameAndType #174:#175 // parseInt:(Ljava/lang/String;)I#126 Utf8 200#127 Utf8 java/util/concurrent/LinkedBlockingDeque#128 NameAndType #51:#52 // queue:Ljava/util/concurrent/LinkedBlockingDeque;#129 Utf8 java/util/concurrent/ThreadPoolExecutor#130 Class #176 // java/util/concurrent/TimeUnit#131 NameAndType #177:#178 // MILLISECONDS:Ljava/util/concurrent/TimeUnit;#132 NameAndType #57:#179 // init:(IIJLjava/util/concurrent/TimeUnit;Ljava/util/concurrent/BlockingQueue;)V#133 NameAndType #180:#181 // allowCoreThreadTimeOut:(Z)V#134 Utf8 com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$2#135 NameAndType #57:#182 // init:(Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;)V#136 NameAndType #183:#184 // setRejectedExecutionHandler:(Ljava/util/concurrent/RejectedExecutionHandler;)V#137 NameAndType #185:#163 // isNull:(Ljava/lang/Object;)Z#138 Utf8 com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$3#139 Utf8 java/lang/Object#140 Utf8 org/springframework/beans/factory/InitializingBean#141 Utf8 java/lang/String#142 Utf8 java/util/Map#143 Utf8 javax/servlet/AsyncContext#144 Utf8 java/util/concurrent/ExecutionException#145 Utf8 java/lang/InterruptedException#146 Utf8 java/lang/Exception#147 Utf8 javax/servlet/http/HttpServletRequest#148 Utf8 getRequestURI#149 Utf8 ()Ljava/lang/String;#150 Utf8 getParameterMap#151 Utf8 ()Ljava/util/Map;#152 Utf8 startAsync#153 Utf8 ()Ljavax/servlet/AsyncContext;#154 Utf8 getRequest#155 Utf8 ()Ljavax/servlet/ServletRequest;#156 Utf8 javax/servlet/ServletRequest#157 Utf8 setAttribute#158 Utf8 (Ljava/lang/String;Ljava/lang/Object;)V#159 Utf8 setTimeout#160 Utf8 (J)V#161 Utf8 java/util/Objects#162 Utf8 nonNull#163 Utf8 (Ljava/lang/Object;)Z#164 Utf8 addListener#165 Utf8 (Ljavax/servlet/AsyncListener;)V#166 Utf8 (Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;Ljava/util/concurrent/Callable;)V#167 Utf8 submit#168 Utf8 (Ljava/util/concurrent/Callable;)Ljava/util/concurrent/Future;#169 Utf8 complete#170 Utf8 java/util/concurrent/Future#171 Utf8 get#172 Utf8 ()Ljava/lang/Object;#173 Utf8 java/lang/Integer#174 Utf8 parseInt#175 Utf8 (Ljava/lang/String;)I#176 Utf8 java/util/concurrent/TimeUnit#177 Utf8 MILLISECONDS#178 Utf8 Ljava/util/concurrent/TimeUnit;#179 Utf8 (IIJLjava/util/concurrent/TimeUnit;Ljava/util/concurrent/BlockingQueue;)V#180 Utf8 allowCoreThreadTimeOut#181 Utf8 (Z)V#182 Utf8 (Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;)V#183 Utf8 setRejectedExecutionHandler#184 Utf8 (Ljava/util/concurrent/RejectedExecutionHandler;)V#185 Utf8 isNull
{public com.common.instance.demo.core.serviceLevel.OneLevelAsyncContext();descriptor: ()Vflags: ACC_PUBLICCode:stack2, locals1, args_size10: aload_01: invokespecial #1 // Method java/lang/Object.init:()V4: aload_05: ldc #2 // String uri7: putfield #3 // Field URI:Ljava/lang/String;10: aload_011: ldc #4 // String params13: putfield #5 // Field PARAMS:Ljava/lang/String;16: returnLineNumberTable:line 23: 0line 25: 4line 26: 10LocalVariableTable:Start Length Slot Name Signature0 17 0 this Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;public java.lang.Object submitFuture(javax.servlet.http.HttpServletRequest, java.util.concurrent.Callablejava.lang.Object) throws java.util.concurrent.ExecutionException, java.lang.InterruptedException;descriptor: (Ljavax/servlet/http/HttpServletRequest;Ljava/util/concurrent/Callable;)Ljava/lang/Object;flags: ACC_PUBLICCode:stack5, locals7, args_size30: aload_11: invokeinterface #6, 1 // InterfaceMethod javax/servlet/http/HttpServletRequest.getRequestURI:()Ljava/lang/String;6: astore_37: aload_18: invokeinterface #7, 1 // InterfaceMethod javax/servlet/http/HttpServletRequest.getParameterMap:()Ljava/util/Map;13: astore 415: aload_116: invokeinterface #8, 1 // InterfaceMethod javax/servlet/http/HttpServletRequest.startAsync:()Ljavax/servlet/AsyncContext;21: astore 523: aload 525: invokeinterface #9, 1 // InterfaceMethod javax/servlet/AsyncContext.getRequest:()Ljavax/servlet/ServletRequest;30: ldc #2 // String uri32: aload_333: invokeinterface #11, 3 // InterfaceMethod javax/servlet/ServletRequest.setAttribute:(Ljava/lang/String;Ljava/lang/Object;)V38: aload 540: invokeinterface #9, 1 // InterfaceMethod javax/servlet/AsyncContext.getRequest:()Ljavax/servlet/ServletRequest;45: ldc #4 // String params47: aload 449: invokeinterface #11, 3 // InterfaceMethod javax/servlet/ServletRequest.setAttribute:(Ljava/lang/String;Ljava/lang/Object;)V54: aload 556: ldc2_w #12 // long 2000l59: invokeinterface #14, 3 // InterfaceMethod javax/servlet/AsyncContext.setTimeout:(J)V64: aload_065: getfield #15 // Field asyncListener:Ljavax/servlet/AsyncListener;68: invokestatic #16 // Method java/util/Objects.nonNull:(Ljava/lang/Object;)Z71: ifeq 8574: aload 576: aload_077: getfield #15 // Field asyncListener:Ljavax/servlet/AsyncListener;80: invokeinterface #17, 2 // InterfaceMethod javax/servlet/AsyncContext.addListener:(Ljavax/servlet/AsyncListener;)V85: aload_086: getfield #18 // Field executor:Ljava/util/concurrent/ThreadPoolExecutor;89: new #19 // class com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$192: dup93: aload_094: aload_295: invokespecial #20 // Method com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$1.init:(Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;Ljava/util/concurrent/Callable;)V98: invokevirtual #21 // Method java/util/concurrent/ThreadPoolExecutor.submit:(Ljava/util/concurrent/Callable;)Ljava/util/concurrent/Future;101: astore 6103: aload 5105: invokeinterface #22, 1 // InterfaceMethod javax/servlet/AsyncContext.complete:()V110: aload 6112: invokeinterface #23, 1 // InterfaceMethod java/util/concurrent/Future.get:()Ljava/lang/Object;117: areturnLineNumberTable:line 34: 0line 36: 7line 39: 15line 40: 23line 41: 38line 43: 54line 44: 64line 45: 74line 49: 85line 58: 103line 59: 110LocalVariableTable:Start Length Slot Name Signature0 118 0 this Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;0 118 1 request Ljavax/servlet/http/HttpServletRequest;0 118 2 task Ljava/util/concurrent/Callable;7 111 3 uri Ljava/lang/String;15 103 4 params Ljava/util/Map;23 95 5 asyncContext Ljavax/servlet/AsyncContext;103 15 6 future Ljava/util/concurrent/Future;LocalVariableTypeTable:Start Length Slot Name Signature0 118 2 task Ljava/util/concurrent/CallableLjava/lang/Object;;15 103 4 params Ljava/util/MapLjava/lang/String;[Ljava/lang/String;;103 15 6 future Ljava/util/concurrent/FutureLjava/lang/Object;;StackMapTable: number_of_entries 1frame_type 254 /* append */offset_delta 85locals [ class java/lang/String, class java/util/Map, class javax/servlet/AsyncContext ]Exceptions:throws java.util.concurrent.ExecutionException, java.lang.InterruptedExceptionMethodParameters:Name Flagsrequest finaltask finalSignature: #89 // (Ljavax/servlet/http/HttpServletRequest;Ljava/util/concurrent/CallableLjava/lang/Object;;)Ljava/lang/Object;public void afterPropertiesSet() throws java.lang.Exception;descriptor: ()Vflags: ACC_PUBLICCode:stack9, locals3, args_size10: ldc #24 // String 1002: invokestatic #25 // Method java/lang/Integer.parseInt:(Ljava/lang/String;)I5: istore_16: ldc #26 // String 2008: invokestatic #25 // Method java/lang/Integer.parseInt:(Ljava/lang/String;)I11: istore_212: aload_013: new #27 // class java/util/concurrent/LinkedBlockingDeque16: dup17: invokespecial #28 // Method java/util/concurrent/LinkedBlockingDeque.init:()V20: putfield #29 // Field queue:Ljava/util/concurrent/LinkedBlockingDeque;23: aload_024: new #30 // class java/util/concurrent/ThreadPoolExecutor27: dup28: iload_129: iload_230: ldc2_w #31 // long 100l33: getstatic #33 // Field java/util/concurrent/TimeUnit.MILLISECONDS:Ljava/util/concurrent/TimeUnit;36: aload_037: getfield #29 // Field queue:Ljava/util/concurrent/LinkedBlockingDeque;40: invokespecial #34 // Method java/util/concurrent/ThreadPoolExecutor.init:(IIJLjava/util/concurrent/TimeUnit;Ljava/util/concurrent/BlockingQueue;)V43: putfield #18 // Field executor:Ljava/util/concurrent/ThreadPoolExecutor;46: aload_047: getfield #18 // Field executor:Ljava/util/concurrent/ThreadPoolExecutor;50: iconst_151: invokevirtual #35 // Method java/util/concurrent/ThreadPoolExecutor.allowCoreThreadTimeOut:(Z)V54: aload_055: getfield #18 // Field executor:Ljava/util/concurrent/ThreadPoolExecutor;58: new #36 // class com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$261: dup62: aload_063: invokespecial #37 // Method com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$2.init:(Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;)V66: invokevirtual #38 // Method java/util/concurrent/ThreadPoolExecutor.setRejectedExecutionHandler:(Ljava/util/concurrent/RejectedExecutionHandler;)V69: aload_070: getfield #15 // Field asyncListener:Ljavax/servlet/AsyncListener;73: invokestatic #39 // Method java/util/Objects.isNull:(Ljava/lang/Object;)Z76: ifeq 9179: aload_080: new #40 // class com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$383: dup84: aload_085: invokespecial #41 // Method com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$3.init:(Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;)V88: putfield #15 // Field asyncListener:Ljavax/servlet/AsyncListener;91: returnLineNumberTable:line 68: 0line 70: 6line 72: 12line 74: 23line 76: 46line 78: 54line 105: 69line 106: 79line 155: 91LocalVariableTable:Start Length Slot Name Signature0 92 0 this Lcom/common/instance/demo/core/serviceLevel/OneLevelAsyncContext;6 86 1 corePoolSize I12 80 2 maxNumPoolSize IStackMapTable: number_of_entries 1frame_type 253 /* append */offset_delta 91locals [ int, int ]Exceptions:throws java.lang.Exception
}
SourceFile: OneLevelAsyncContext.java
RuntimeVisibleAnnotations:0: #98()
InnerClasses:#40; //class com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$3#36; //class com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$2#19; //class com/common/instance/demo/core/serviceLevel/OneLevelAsyncContext$1 四、字节码指令 Java各种语法、关键字、常量变量、符号运算的语义最终都会由多个字节码指令组合来表达。Java虚拟机字节码指令组成如下所示操作码Opcode、操作数Operand。 Java虚拟机面向操作数栈而不是面向寄存器的架构其总数不超过256条单字节指令分类如下表所示。 指令类型 指令作用 指令 加载和存储 局部表加载到操作数栈 1.iload、iload_n、aload、aload_n、...... 2._n其中n表示局部变量表的slot索引位置。 操作数栈存储到局部表 1.istore、istore_n、astore、astore_n、...... 2._n其中n表示局部变量表的slot索引位置。 常量加载到操作数栈 1.iconst_i、aconst_null、bipush、sipush、ldc、...... 2.iconst_i表示int型的常量i加载到操作数栈。 扩充局部变量表的访问索引 wide 运算指令 加法指令 iadd、ladd、fadd、dadd 减法指令 isub、lsub、fsub、dsub 局部变量自增指令 iinc 比较指令 dcmpg、dcmpl、fcmpg、fcmpl、cmp ...... imul、idev、irem、ineg、ishl、ior、iadd、ixor、...... 对象创建和访问 类实例创建 new 数组创建 newarray、anewarray、multianewarray 访问实例字段或类字段 getfield、putfield、getstatic、putstatic 数组元素加载到操作数栈 iaload、aaload、...... 操作数栈存储到数组元素 iastore、aastore、...... 获取数组长度 arraylength 检查类实例类型 instanceof、checkcast 操作数栈管理 栈顶一个或两个元素出栈 pop、pop2 栈顶一个或两个元素复制或双份复制重新压入栈顶 dup、dup2、dup_x1、dup2_x1、dup_x2、dup2_x2 最顶端两个元素互换 swap 控制转移 条件分支 ifeq、iflt、ifnull、ificmplt、ifacmpeq、...... 复合条件分支 tableswitch、lookupswitch 无条件分支 goto、goto_w、...... 方法调用和返回 调用对象实例方法 invokevirtual运行时实际类型进行动态分派 _ 重写 调用接口方法 invokeinterface运行时实现该接口的对象找到合适则调用 调用实例初始化、私有、父类方法 invokespecial实例初始化、私有、父类方法 调用类静态方法 invokestaticstatic方法 动态调用用户设定的方法 invokedunamic运行时动态解析调用点限定符所引用的方法 方法返回 1.returnvoid、实例初始化、类或接口初始化方法 2.ireturn、lreturn、freturn、dreturn、areturn byte、short、char、boolean、int型返回使用ireturn 异常处理 显示抛出异常 athrowthrow语句 检测到异常状况自动抛出 同步处理 synchronized加锁 都是使用管程Monitor 1.方法的隐式加锁即方法访问标志ACC_SYNCHRONIZED; 2.语句块的显示加锁即monitorenter monitorexit 类型转换 宽化类型转换安全转换 JVM直接支持i转l/f/d、l转f/d、f转d 窄化类型转换强制转换 i2b、i2c、i2s、l2i、f2l、d2f、...... 注意: a.i代表int、l代表long、s代表short、b代表byte、c代表char、f代表float、d代表double、a代表reference型 b.JVM不直接支持byte、short、char、boolean类型的算术运算转换为int型运算 c.算术指令对操作数栈顶的两个元素运算运算后先移除这两个元素后计算结果存入栈顶 d.invokevirtual、invokeinterface、invokespecial、invokestatic调用都固化在JVM内部而invokedunamic是由用户所设定的引导方法决定的 e.方法无论正常结果还是异常结束则每条monitorenter都必须对应monitorexit f.算术运算时使用NaNNot a Number运算其结果都是NaN。
五、参考资料
jdk/jdk12: log
Java 进阶之字节码剖析_aload_0_C陈三岁的博客-CSDN博客
Class文件解析_class 详解_Aur_ora的博客-CSDN博客
