BTrace入門

package com.dianping.data;
import java.util.Random;

/**
 * @author star.li
 * @date 16/4/14.
 */
public class Case1{
    public static void main(String[] args) throws Exception{
        Random random=new Random();
        CaseObject object=new CaseObject();
        boolean result=true;
        while(result){
            result=object.execute(random.nextInt(1000));
            Thread.sleep(1000);
        }
    }
}

package com.dianping.data;

/**
 * @author star.li
 * @date 16/4/14.
 */
public class CaseObject {
    private static int sleepTotalTime=0;

    public boolean execute(int sleepTime) throws Exception{
        System.out.println("sleep: "+sleepTime);
        sleepTotalTime+=sleepTime;
        Thread.sleep(sleepTime);
        return true;
    }
}

4.有沒有人調用CaseObject中的特定某行代碼？

1.監控函數的參數、返回值、靜態類成員變量

import com.sun.btrace.annotations.*;
import static com.sun.btrace.BTraceUtils.*;
import com.dianping.data.*;

@BTrace public class TraceMethodArgsAndReturn {

    @OnMethod(
      clazz="com.dianping.data.CaseObject",
      method="execute",
      location=@Location(Kind.RETURN)
   )
   public static void traceExecute(@Self CaseObject instance,int sleepTime,@Return boolean result){
     println("call CaseObject.execute");
     println(strcat("sleepTime is:",str(sleepTime)));
     println(strcat("sleepTotalTime is:",str(get(field("com.dianping.data.CaseObject","sleepTotalTime"),instance))));
     println(strcat("return value is:",str(result)));
   }
}

import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.*;
 
@BTrace public class TraceMethodExecuteTime{
    
   @TLS static long beginTime;
 
   @OnMethod(
      clazz="com.dianping.data.CaseObject",
      method="execute"
   )
   public static void traceExecuteBegin(){
     beginTime=timeMillis();
   }
 
   @OnMethod(
      clazz="com.dianping.data.CaseObject",
      method="execute",
      location=@Location(Kind.RETURN)
   )
   public static void traceExecute(){
      println(strcat(strcat("CaseObject.execute time is:",str(timeMillis()-beginTime)),"ms"));
   }
}

import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.*;
 
@BTrace public class TraceMethodCallee{
   @OnMethod(
      clazz="com.dianping.data.CaseObject",
      method="execute"
   )
   public static void traceExecute(){
     println("who call CaseObject.execute :");
     jstack(); 
   }
}

import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.*;
 
@BTrace public class TraceMethodLine{
   @OnMethod(
      clazz="com.dianping.data.CaseObject",
      location=@Location(value=Kind.LINE,line=11)
   )
   public static void traceExecute(@ProbeClassName String pcn,@ProbeMethodName String pmn,int line){
     println(strcat(strcat(strcat(strcat(strcat("call ",pcn),"."),pmn),"at line:"),str(line)));
   }
}

需要注意的一點是，btrace監控退出後，修改過的class不會被恢復，你的所有的監控代碼依然一直在運行。每次執行你的監控代碼之前會先進行一個判斷，判斷當前是否處於監控中。你的客戶端發起了exit指令後，該方法判斷false，直接return。所以btrace使用退出後會讓你的代碼多走了一個方法調用+一個對象屬性判斷.

使用JVisualVM的BTrace插件

1.安裝BTrace插件

打開VisualVM的工具—插件，在可用插件列表中選擇BTrace Workbench進行安裝

2.選擇java應用，右鍵選擇Trace application...即可打卡BTrace界面

3.在打開的BTrace界面中編寫監控腳本代碼，並執行(可根據需要調整classpath)