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mini-jvm.drawio
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<mxfile host="Electron" modified="2024-04-19T15:56:49.815Z" agent="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) draw.io/21.6.5 Chrome/114.0.5735.243 Electron/25.3.1 Safari/537.36" etag="8etbdHrPRuGhRPIH-kHP" version="21.6.5" type="device">
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<mxCell id="eWhodD4vRtD6RhS1Q6ua-54" value="<div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">main(String[] args) 方法体<br style="font-size: 10px;">{</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; &nbsp; System.out.println("hello");</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">}</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">被编译为下面4条字节码指令:</font></div><div style=""><font color="#007fff" style=""><div style="font-size: 10px;">&nbsp;GETSTATIC java/lang/System.out : Ljava/io/PrintStream;<span style=""><span style="">&nbsp;&nbsp;&nbsp;&nbsp;</span></span><b>//即从 java/lang/System 类中获取 out 静态字段 返回为 PrintStream 类型</b></div><div style="font-size: 10px;">&nbsp;LDC "hello"</div><div style="font-size: 10px;">&nbsp;INVOKEVIRTUAL java/io/PrintStream.println (Ljava/lang/String;)V<span style=""><span style="">&nbsp;&nbsp;&nbsp;&nbsp;</span></span><b style="background-color: initial; border-color: var(--border-color);">//即调用 java/io/PrintStream println(Ljava/lang/String;)V 方法</b></div></font><font color="#007fff" style=""><div style="font-size: 10px;">&nbsp;<span style="background-color: initial;">RETURN</span></div><div style="font-size: 10px;"><span style="background-color: initial;"><br></span></div><div style=""><div style="">{Integer@1734} 0 -&gt; {<b>GetStaticInst</b>@1735} "GetStaticInst{clazz='java/lang/System', fieldName='out', fieldDescriptor='Ljava/io/PrintStream;'}"</div><div style="">&nbsp;key = {Integer@1734} 0</div><div style="">&nbsp;value = {GetStaticInst@1735} "GetStaticInst{clazz='java/lang/System', fieldName='out', fieldDescriptor='Ljava/io/PrintStream;'}"</div><div style="">&nbsp; <b>clazz</b> = "java/lang/System"</div><div style="">&nbsp; <b>fieldName</b> = "out"</div><div style="">&nbsp; <b>fieldDescriptor</b> = "Ljava/io/PrintStream;"</div><div style="">{Integer@1736} 3 -&gt; {<b>LdcInst</b>@1737} "LdcInst{descriptor='Ljava/lang/String', val=hello}"</div><div style="">&nbsp;key = {Integer@1736} 3</div><div style="">&nbsp;value = {LdcInst@1737} "LdcInst{descriptor='Ljava/lang/String', val=hello}"</div><div style="">&nbsp; <b>descriptor</b> = "Ljava/lang/String"</div><div style="">&nbsp; <b>val</b> = "hello"</div><div style="">{Integer@1738} 5 -&gt; {<b>InvokeVirtualInst</b>@1739} "InvokeVirtualInst{clazz='java/io/PrintStream', methodName='println', methodDescriptor='(Ljava/lang/String;)V'}"</div><div style="">&nbsp;key = {Integer@1738} 5</div><div style="">&nbsp;value = {InvokeVirtualInst@1739} "InvokeVirtualInst{clazz='java/io/PrintStream', methodName='println', methodDescriptor='(Ljava/lang/String;)V'}"</div><div style="">&nbsp; <b>clazz</b> = "java/io/PrintStream"</div><div style="">&nbsp; <b>methodName</b> = "println"</div><div style="">&nbsp; <b>methodDescriptor</b> = "(Ljava/lang/String;)V"</div><div style="">{Integer@1740} 8 -&gt; {ReturnInst@1741}&nbsp;</div></div><div style="font-size: 10px;"><br></div></font></div>" style="text;html=1;align=left;verticalAlign=top;resizable=0;points=[];autosize=1;strokeColor=none;fillColor=none;fontSize=10;" vertex="1" parent="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-1" value="<h1 style="font-size: 18px;"><font style="font-size: 18px;">Mini-jvm 工作原理</font></h1><div style=""><div style=""><font style="font-size: 12px;">参考 Java8 HotSpot 实现的开源的简单的JVM实现，jvm-core 除去 Instuction (字节码指令实现) 也就剩下大概 7K多行，很容易理解。<br>不过功能也只包含一些很核心的功能。</font></div><div style=""><font style="font-size: 12px;">https://github.com/guxingke/mini-jvm</font><br></div></div>" style="text;html=1;strokeColor=none;fillColor=none;spacing=5;spacingTop=-20;whiteSpace=wrap;overflow=hidden;rounded=0;fontSize=16;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-2" value="Main#main(String[] args)<br><font color="#007fff">位于jvm-core模块</font>" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#d5e8d4;strokeColor=#82b366;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-3" value="Args cmd = Args.parseArgs(args);<br><div><font color="#007fff">主要是解析 -cp -jar 获取类加载路径</font></div><div><font color="#007fff">以及获取Main类全限定名</font></div>" style="rounded=1;whiteSpace=wrap;html=1;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-9" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=1;orthogonalLoop=1;jettySize=auto;html=1;" parent="1" source="hw3rN0ojpoE_x7gTb8zc-5" target="hw3rN0ojpoE_x7gTb8zc-8" edge="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-5" value="VirtualMachine vm = new <b>VirtualMachine</b>();<br><font color="#007fff">这个类并没有任何成员字段</font>" style="rounded=1;whiteSpace=wrap;html=1;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-7" value="<p style="margin:0px;margin-top:4px;text-align:center;"><b>Args</b></p><hr size="1"><p style="margin:0px;margin-left:4px;">boolean version;</p><p style="margin:0px;margin-left:4px;">boolean help;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//是否启用详细日志输出，打开的话会输出详细的运行日志</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//作者支持了trace call class debug</font></p><p style="margin:0px;margin-left:4px;">boolean <b>verbose</b>;</p><p style="margin:0px;margin-left:4px;">boolean verboseTrace;</p><p style="margin:0px;margin-left:4px;">boolean verboseCall;</p><p style="margin:0px;margin-left:4px;">boolean verboseClass;</p><p style="margin:0px;margin-left:4px;">boolean verboseDebug;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//解析 -cp -jar 参数获取到的类路径</font></p><p style="margin:0px;margin-left:4px;">public String <b>classpath</b> = ".";</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//应用的Main类全限定名</font></p><p style="margin:0px;margin-left:4px;">public String <b>clazz</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//原始参数列表</font></p><p style="margin:0px;margin-left:4px;">public String[] <b>args</b> = new String[0];</p><hr size="1"><p style="margin:0px;margin-left:4px;">public static Args <b>parseArgs</b>(String... cliArgs)<br></p>" style="verticalAlign=top;align=left;overflow=fill;fontSize=12;fontFamily=Helvetica;html=1;whiteSpace=wrap;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-8" value="vm.<b>run</b>(cmd);" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#fff2cc;strokeColor=#d6b656;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-14" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=1;orthogonalLoop=1;jettySize=auto;html=1;" parent="1" source="hw3rN0ojpoE_x7gTb8zc-10" target="hw3rN0ojpoE_x7gTb8zc-13" edge="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-10" value="先将 Args 对象的参数再记录到 EnvHolder 中" style="rounded=1;whiteSpace=wrap;html=1;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-12" value="<p style="margin:0px;margin-top:4px;text-align:center;"><b>EnvHolder</b><br></p><hr size="1"><p style="margin:0px;margin-left:4px;">public static boolean verbose;</p><p style="margin:0px;margin-left:4px;">public static boolean verboseTrace;</p><p style="margin:0px;margin-left:4px;">public static boolean verboseCall;</p><p style="margin:0px;margin-left:4px;">public static boolean verboseClass;</p><p style="margin:0px;margin-left:4px;">public static boolean verboseDebug;</p><p style="margin:0px;margin-left:4px;">public static boolean debug;</p><hr size="1"><p style="margin:0px;margin-left:4px;"><br></p>" style="verticalAlign=top;align=left;overflow=fill;fontSize=12;fontFamily=Helvetica;html=1;whiteSpace=wrap;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-13" value="Entry entry = Classpath.parse(Utils.classpath(<br>cmd.classpath));<br><font style="font-size: 10px;" color="#007fff">先获取类路径，再解析类路径到Entry实例</font>" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#dae8fc;strokeColor=#6c8ebf;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-32" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=1;orthogonalLoop=1;jettySize=auto;html=1;" parent="1" source="hw3rN0ojpoE_x7gTb8zc-15" target="hw3rN0ojpoE_x7gTb8zc-31" edge="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-15" value="ClassLoader classLoader = new <b>ClassLoader</b>("boot", entry);<br><b>initVm</b>(classLoader);<br><font color="#007fff">创建boot类加载器，初始化JVM</font>" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#dae8fc;strokeColor=#6c8ebf;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-17" value="<div>String mainClass = Utils.replace(<br>cmd.clazz, '.', EnvHolder<br>.FILE_SEPARATOR.toCharArray([0]);<span style="background-color: initial;">&nbsp; &nbsp; classLoader.<b>loadClass</b>(mainClass);</span></div><div><font color="#007fff">主类的类加载</font></div>" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#dae8fc;strokeColor=#6c8ebf;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-22" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=1;orthogonalLoop=1;jettySize=auto;html=1;" parent="1" source="hw3rN0ojpoE_x7gTb8zc-19" target="hw3rN0ojpoE_x7gTb8zc-21" edge="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-19" value="Class clazz = Heap.findClass(mainClass);<br>Method method = clazz.getMainMethod();<br><font color="#007fff">查找应用程序Main类的main()方法</font>" style="rounded=1;whiteSpace=wrap;html=1;" parent="1" vertex="1">
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<mxCell id="eWhodD4vRtD6RhS1Q6ua-15" value="" style="edgeStyle=orthogonalEdgeStyle;rounded=1;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="hw3rN0ojpoE_x7gTb8zc-21" target="eWhodD4vRtD6RhS1Q6ua-14">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-21" value="Interpreter.<b>runMain</b>(method, cmd.args);<br><font color="#007fff">解析器执行main()方法</font>" style="rounded=1;whiteSpace=wrap;html=1;fillColor=#dae8fc;strokeColor=#6c8ebf;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-24" value="args.clazz = parseMainClass(jar);<br><font color="#007fff">解析Java包中的Main类：通过解析META-INF/MANIFEST.MF文件中 Main-Class属性获取</font>" style="rounded=1;whiteSpace=wrap;html=1;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-26" value="<font color="#007fff">比如测试中最终引入的类路径（可以看到将JDK的jar包也都引进来了，因为mini-jvm并没有实现多少JDK上的实现）：&nbsp;<br>example:/home/arvin/mywork/github/mini-jvm/mini-jdk/target/rt.jar:/home/arvin/.jabba/jdk/[email protected]/jre/lib/*<br>此时 Entry 是 CompositeEntry 类型<br></font>" style="text;html=1;align=left;verticalAlign=middle;resizable=0;points=[];autosize=1;strokeColor=none;fillColor=none;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-27" value="<p style="margin:0px;margin-top:4px;text-align:center;"><b>Entry (I)</b><br></p><hr size="1"><p style="margin:0px;margin-left:4px;"><font color="#007fff">类搜索接口，有3种实现，DirEntry JarEntry CompositeEntry</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">实现类也是 classPath 的容器</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff"><br></font></p><p style="margin:0px;margin-left:4px;">ClassFile findClass(String name);<br></p>" style="verticalAlign=top;align=left;overflow=fill;fontSize=12;fontFamily=Helvetica;html=1;whiteSpace=wrap;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-40" value="<p style="margin:0px;margin-top:4px;text-align:center;"><b>Thread</b><br></p><hr size="1"><p style="margin:0px;margin-left:4px;"><font color="#007fff">内部线程，是一个栈结构，看它的源码实现这其实是栈帧的容器</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff"><br></font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//top其实是栈帧数量，top-1是栈顶的索引</font></p><p style="margin:0px;margin-left:4px;">public int top;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//保存栈帧的栈</font></p><p style="margin:0px;margin-left:4px;">public Frame[] frames;</p><hr size="1"><p style="margin:0px;margin-left:4px;">public void pushFrame(Frame frame)&nbsp;<br></p><p style="margin:0px;margin-left:4px;">public Frame popFrame()<br></p><p style="margin:0px;margin-left:4px;">public Frame topFrame()<br></p><p style="margin:0px;margin-left:4px;">public Frame callerFrame()<br></p>" style="verticalAlign=top;align=left;overflow=fill;fontSize=12;fontFamily=Helvetica;html=1;whiteSpace=wrap;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-41" value="<p style="margin:0px;margin-top:4px;text-align:center;"><b>Frame</b><br></p><hr size="1"><p style="margin:0px;margin-left:4px;"><font color="#007fff"><b>栈帧</b></font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff"><br></font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//当前栈帧执行的方法</font></p><p style="margin:0px;margin-left:4px;">public final Method <b>method</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//本地变量列表, LocalVars 是 Slot 数组</font></p><p style="margin:0px;margin-left:4px;">private final LocalVars <b>localVars</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//操作数栈，是 Slot 栈，除了Slot数组还包含一个top(栈顶索引)</font></p><p style="margin:0px;margin-left:4px;">private final OperandStack <b>operandStack</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//com.gxk.jvm.rtda.heap.</font><font color="#007fff">Method的 instructionMap</font></p><p style="margin:0px;margin-left:4px;">private final Map&lt;Integer, Instruction&gt; <b>instructionMap</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//即MetaSpace栈帧容器main</font></p><p style="margin:0px;margin-left:4px;">public final Thread <b>thread</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//下一个指令的程序计数器值</font></p><p style="margin:0px;margin-left:4px;">public int <b>nextPc</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//当前指令的程序计数器值</font></p><p style="margin:0px;margin-left:4px;">private int <b>pc</b>;</p><p style="margin:0px;margin-left:4px;">public int <b>stat</b>;</p><hr size="1"><p style="margin:0px;margin-left:4px;"><br></p>" style="verticalAlign=top;align=left;overflow=fill;fontSize=12;fontFamily=Helvetica;html=1;whiteSpace=wrap;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-46" value="<p style="margin:0px;margin-top:4px;text-align:center;"><b>Heap</b><br></p><hr size="1"><p style="margin:0px;margin-left:4px;"><font color="#007fff">堆空间，对标的HotSpot中的堆</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff"><br></font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//本地方法的Map</font></p><p style="margin: 0px 0px 0px 4px;"><span style="font-size: 11px;">private static final Map&lt;String, </span><b style="font-size: 11px;">NativeMethod</b><span style="font-size: 11px;">&gt; </span><font style="font-size: 10px;">NATIVE_METHOD_MAP</font><span style="font-size: 11px;">;</span><br></p><p style="margin: 0px 0px 0px 4px; font-size: 11px;"><font color="#007fff">// Klass的Map</font></p><p style="margin: 0px 0px 0px 4px; font-size: 11px;">private static final Map&lt;String, <b>Class</b>&gt; <font style="font-size: 11px;">STRING_K_CLASS_MAP</font>;<br></p><hr size="1"><p style="margin:0px;margin-left:4px;">public static void registerMethod(String key, NativeMethod method)<br></p><p style="margin:0px;margin-left:4px;">public static NativeMethod findMethod(String key)<br></p><p style="margin:0px;margin-left:4px;">public static Class findClass(String name)<br></p><p style="margin:0px;margin-left:4px;">public static void registerClass(String name, Class clazz)<br></p><p style="margin:0px;margin-left:4px;">public static List&lt;Class&gt; getClasses()<br></p>" style="verticalAlign=top;align=left;overflow=fill;fontSize=12;fontFamily=Helvetica;html=1;whiteSpace=wrap;fillColor=#dae8fc;strokeColor=#6c8ebf;" parent="1" vertex="1">
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<mxCell id="hw3rN0ojpoE_x7gTb8zc-47" value="<font color="#007fff">//加载官方JDK中的Class类<br></font>Class metaClass = classLoader<br>.<b>loadClass</b>("java/lang/Class");<br><font color="#007fff">//遍历Heap中注册的类名，依次进行实例化<br></font><div>for (Class cls : Heap.getClasses()) {</div><div>&nbsp; &nbsp; if (cls.getRuntimeClass() == null) {</div><div>&nbsp; &nbsp; Instance obj = metaClass.<b>newInstance</b>();</div><div>&nbsp; &nbsp; cls.setRuntimeClass(obj);</div><div>&nbsp; &nbsp; obj.setMetaClass(cls);</div><div>&nbsp; &nbsp; }</div><div>}</div>" style="rounded=1;whiteSpace=wrap;html=1;arcSize=4;align=left;" parent="1" vertex="1">
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<mxCell id="eWhodD4vRtD6RhS1Q6ua-1" value="<p style="margin:0px;margin-top:4px;text-align:center;"><b>ClassFile</b><br></p><hr size="1"><p style="margin:0px;margin-left:4px;"><font color="#007fff">.class文件读取后的文件对象实例</font></p><p style="margin:0px;margin-left:4px;"><br></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//魔数,确认是否能让虚拟机接受的class文件 在java中 通常为0xCAFEBABE</font></p><p style="margin:0px;margin-left:4px;">public final int magic;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//jvm的次版本号</font></p><p style="margin:0px;margin-left:4px;">public final int minorVersion;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//jvm的主版本号</font></p><p style="margin:0px;margin-left:4px;">public final int majorVersion;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//常量池大小 用来解析后面的常量池</font></p><p style="margin:0px;margin-left:4px;">public final int constantPoolSize;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//常量池结构</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//其中类如果没写继承任何其他类则默认继承Object</font></p><p style="margin:0px;margin-left:4px;">public final ConstantPool <b>cpInfo</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//类访问标志,16位的“bitmask”指出class文件定义的是类还是接口，</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">访问级别是public还是private，</font></p><p style="margin:0px;margin-left:4px;">public final int <b>accessFlags</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//类索引(是常量池索引),class文件存储的类名类似完全限定名</font></p><p style="margin:0px;margin-left:4px;">public final int thisClass;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//父类索引,同上</font></p><p style="margin:0px;margin-left:4px;">public final int <b>superClass</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//接口索引数</font></p><p style="margin:0px;margin-left:4px;">public final int interfacesCount;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//接口索引表，给出该类实现的所有接口的名字</font></p><p style="margin:0px;margin-left:4px;">public final Interfaces interfaces;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//字段数</font></p><p style="margin:0px;margin-left:4px;">public final int fieldCount;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//字段结构，存储字段信息</font></p><p style="margin:0px;margin-left:4px;">public final Fields fields;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//方法数</font></p><p style="margin:0px;margin-left:4px;">public final int methodsCount;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//方法结构，存储方法信息</font></p><p style="margin:0px;margin-left:4px;">public final Methods methods;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//属性数</font></p><p style="margin:0px;margin-left:4px;">public final int attributesCount;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//属性结构，存储属性信息，</font><font color="#007fff">比如源码文件名（SourceFile）、</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">代码属性(Code)、异常处理表、行号表、局部变量表、常量表、</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">注解属性等</font></p><p style="margin:0px;margin-left:4px;">public final Attributes <b>attributes</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//class文件路径</font></p><p style="margin:0px;margin-left:4px;">private String source;</p><hr size="1"><p style="margin:0px;margin-left:4px;"><br></p>" style="verticalAlign=top;align=left;overflow=fill;fontSize=12;fontFamily=Helvetica;html=1;whiteSpace=wrap;" vertex="1" parent="1">
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<mxCell id="eWhodD4vRtD6RhS1Q6ua-5" value="<p style="margin:0px;margin-top:4px;text-align:center;"><b>Method</b><br></p><hr size="1"><p style="margin:0px;margin-left:4px;"><font color="#007fff">对标HotSpot的<b>KMethod</b>类</font></p><p style="margin:0px;margin-left:4px;"><br></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//方法的访问标志，如public private，</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">其中&amp;0x0100这位表示是否是本地方法</font></p><p style="margin:0px;margin-left:4px;"><font color="#007fff">&amp;0x0008这位表示是否是静态方法<br></font></p><p style="margin:0px;margin-left:4px;">public final int <b>accessFlags</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//方法名</font></p><p style="margin:0px;margin-left:4px;">public final String <b>name</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//参数以及返回值类型</font></p><p style="margin:0px;margin-left:4px;">public final String <b>descriptor</b>;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//操作数栈最大size</font></p><p style="margin:0px;margin-left:4px;">public final int maxStacks;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//本地变量表最大长度</font></p><p style="margin:0px;margin-left:4px;">public final int maxLocals;</p><p style="margin:0px;margin-left:4px;"><font color="#007fff">//指令Map，就是代码块中包含的字节码指令Map</font></p><p style="margin:0px;margin-left:4px;">public final Map&lt;Integer, Instruction&gt; <b>instructionMap</b>;</p><p style="margin:0px;margin-left:4px;">public final ExceptionTable exceptionTable;</p><p style="margin:0px;margin-left:4px;">public final LineNumberTable lineNumberTable;</p><p style="margin:0px;margin-left:4px;"><br></p><p style="margin:0px;margin-left:4px;">public Class clazz;</p><hr size="1"><p style="margin:0px;margin-left:4px;"><br></p>" style="verticalAlign=top;align=left;overflow=fill;fontSize=12;fontFamily=Helvetica;html=1;whiteSpace=wrap;" vertex="1" parent="1">
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<mxCell id="eWhodD4vRtD6RhS1Q6ua-7" value="<div style="font-size: 11px;"><span style="background-color: initial; font-size: 11px;"><font color="#007fff" style="font-size: 11px;">//MethodInfo -&gt; Method</font></span></div><div style="font-size: 11px;"><span style="background-color: initial; font-size: 11px;">methods.add(this.</span><b style="background-color: initial; font-size: 11px;">map</b><span style="background-color: initial; font-size: 11px;">(methodInfo));</span></div><div style="font-size: 11px;">...</div><div style="font-size: 11px;"><font color="#007fff" style="font-size: 11px;">//FieldInfo -&gt; Field</font></div>fields.add(this.map(fieldInfo));<br style="font-size: 11px;">...<br style="font-size: 11px;"><font color="#007fff" style="font-size: 11px;">//执行字段的静态初始化方法<br style="font-size: 11px;"></font><div style="font-size: 11px;">for (Field it : fields) {</div><div style="font-size: 11px;">&nbsp; if (it.isStatic()) {</div><div style="font-size: 11px;">&nbsp; &nbsp; it.<b>init</b>();</div><div style="font-size: 11px;">&nbsp; }</div><div style="font-size: 11px;">}</div><div style="font-size: 11px;">...</div><div style="font-size: 11px;"><font color="#007fff" style="font-size: 11px;">//超类类名（常量池中索引scIdx位置），这里可以看到Java只能单继承</font></div><div style="font-size: 11px;">superClassName = Utils.getClassName(classFile.cpInfo, scIdx);<br style="font-size: 11px;"></div><div style="font-size: 11px;">...</div><div style="font-size: 11px;"><font color="#007fff" style="font-size: 11px;">//实现的接口类名</font></div><div style="font-size: 11px;">interfaceNames.add(anInterface.getName());<br style="font-size: 11px;"></div><div style="font-size: 11px;">...</div><div style="font-size: 11px;">BootstrapMethods bootstrapMethods = classFile.getBootstrapMethods();<br style="font-size: 11px;"></div><div style="font-size: 11px;"><font color="#007fff" style="font-size: 11px;">//<b>即类加载就是将class文件转成Class对象,对标HotSpot中的Klass</b></font></div><div style="font-size: 11px;"><div style="font-size: 11px;">return new <b style="font-size: 11px;">Class</b>(classFile.accessFlags, name, superClassName, interfaceNames, methods, fields,&nbsp;<span style="background-color: initial; font-size: 11px;">bootstrapMethods, classFile.cpInfo, this, classFile);</span></div></div>" style="rounded=1;whiteSpace=wrap;html=1;align=left;arcSize=3;fontSize=11;" vertex="1" parent="1">
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<mxCell id="eWhodD4vRtD6RhS1Q6ua-13" value="<font color="#007fff">就是遍历 clazz 中所有方法，寻找名为 main 的方法<br>注意这里 Class Method 对标HotSpot 中的Klass KMethod<br></font>" style="text;html=1;align=left;verticalAlign=middle;resizable=0;points=[];autosize=1;strokeColor=none;fillColor=none;" vertex="1" parent="1">
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<mxCell id="eWhodD4vRtD6RhS1Q6ua-14" value="<div style="font-size: 11px;"><font color="#007fff">//先创建一个方法栈帧</font></div><div style="font-size: 11px;">Frame frame = new <b>Frame</b>(method);</div><div style="font-size: 11px;"><font color="#007fff">//参数实例列表</font></div><div style="font-size: 11px;">Instance[] kargs = new <b>Instance</b>[args.length];</div><div style="font-size: 11px;">for (int i = 0; i &lt; args.length; i++) {</div><div style="font-size: 11px;">&nbsp; kargs[i] = Utils.str2Obj(args[i], frame.method.clazz.classLoader);</div><div style="font-size: 11px;">}</div><div style="font-size: 11px;"><font color="#007fff">//其实就是检查 java.lang.String 是否加载，未加载则执行加载并存到堆中</font></div><div style="font-size: 11px;">Class arrClazz = Heap.findClass("[Ljava/lang/String;");</div><div style="font-size: 11px;">if (arrClazz == null) {</div><div style="font-size: 11px;">&nbsp; arrClazz = new Class(1, "[Ljava/lang/String;", method.clazz.classLoader, null);</div><div style="font-size: 11px;">&nbsp; Heap.registerClass(arrClazz.name, arrClazz);</div><div style="font-size: 11px;">}</div><div style="font-size: 11px;"><font color="#007fff">//Instance[] -&gt; InstanceArray</font></div><div style="font-size: 11px;">InstanceArray array = new <b>InstanceArray</b>(arrClazz, kargs);</div><div style="font-size: 11px;"><font color="#007fff">//参数作为本地变量</font></div><div style="font-size: 11px;">frame.<b>setRef</b>(0, array);</div><div style="font-size: 11px;"><br style="font-size: 11px;"></div><div style="font-size: 11px;"><b>execute</b>(frame);</div>" style="rounded=1;whiteSpace=wrap;html=1;align=left;arcSize=3;fontSize=11;" vertex="1" parent="1">
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<mxCell id="eWhodD4vRtD6RhS1Q6ua-39" value="<font color="#007fff" style="font-size: 10px;">比如执行 Hello#main(String args) 方法创建的栈帧：<br style="font-size: 10px;"><div style="font-size: 10px;">public static void main(String[] args) {</div><div style="font-size: 10px;">&nbsp; &nbsp; System.out.println("hello");</div><div style="font-size: 10px;">}</div><div style="font-size: 10px;">对应的字节码：</div><div style="font-size: 10px;"><div style="font-size: 10px;">public static main([Ljava/lang/String;)V</div><div style="font-size: 10px;">&nbsp; &nbsp;L0</div><div style="font-size: 10px;">&nbsp; &nbsp; LINENUMBER 3 L0</div><div style="font-size: 10px;">&nbsp; &nbsp; <b>GETSTATIC</b> java/lang/System.out : Ljava/io/PrintStream;</div><div style="font-size: 10px;">&nbsp; &nbsp; <b>LDC</b> "hello"</div><div style="font-size: 10px;">&nbsp; &nbsp; <b>INVOKEVIRTUAL</b> java/io/PrintStream.println (Ljava/lang/String;)V</div><div style="font-size: 10px;">&nbsp; &nbsp;L1</div><div style="font-size: 10px;">&nbsp; &nbsp; LINENUMBER 4 L1</div><div style="font-size: 10px;">&nbsp; &nbsp; <b>RETURN</b></div><div style="font-size: 10px;">&nbsp; &nbsp;L2</div><div style="font-size: 10px;">&nbsp; &nbsp; LOCALVARIABLE args [Ljava/lang/String; L0 L2 0</div><div style="font-size: 10px;">&nbsp; &nbsp; MAXSTACK = 2</div><div style="font-size: 10px;">&nbsp; &nbsp; MAXLOCALS = 1</div></div><br style="font-size: 10px;"></font><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">frame = {Frame@1710}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp;<b style="font-size: 10px;">method</b> = {Method@1193}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp;<b style="font-size: 10px;">localVars</b> = {LocalVars@1717}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; slots = {Slot[1]@1748}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp;<b style="font-size: 10px;">operandStack</b> = {OperandStack@1720}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; slots = {Slot[2]@1749}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; top = 0</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp;<b style="font-size: 10px;">instructionMap</b> = {LinkedHashMap@1712}&nbsp; size = 4</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; {Integer@1734} 0 -&gt; {GetStaticInst@1735} "GetStaticInst{clazz='java/lang/System', fieldName='out', fieldDescriptor='Ljava/io/PrintStream;'}"</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; {Integer@1736} 3 -&gt; {LdcInst@1737} "LdcInst{descriptor='Ljava/lang/String', val=hello}"</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; {Integer@1738} 5 -&gt; {InvokeVirtualInst@1739} "InvokeVirtualInst{clazz='java/io/PrintStream', methodName='println', methodDescriptor='(Ljava/lang/String;)V'}"</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; {Integer@1740} 8 -&gt; {ReturnInst@1741}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp;<b style="font-size: 10px;">thread</b> = {Thread@1723}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; top = 0</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp; frames = {Frame[1024]@1753}&nbsp;</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp;<b style="font-size: 10px;">nextPc</b> = 0</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp;<b style="font-size: 10px;">pc</b> = 0</font></div><div style="font-size: 10px;"><font color="#007fff" style="font-size: 10px;">&nbsp;<b style="font-size: 10px;">stat</b> = 0</font></div>" style="text;html=1;align=left;verticalAlign=middle;resizable=0;points=[];autosize=1;strokeColor=none;fillColor=none;fontSize=10;" vertex="1" parent="1">
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