BTrace

在项目中有时候项目运行上线了碰到了问题，比如想看一个方法运行了多长时间，或者一个方法的返回参数和入参是多少，在不知道btrace的时候，只能更换class加入日志然后重启项目进行问题的定位，但是如果有了btrace  可以再遇到问题的时候在方法上面动态的增加观察 还没必要去在原来代码里面加入代码然后重启项目。

首先要下载btrace的包，这个包可以去btrace的官网下载，然后安装也很简单 是绿色版的，直接把包的bin目录配置到坏境变量里面即可：

1：计算一个类产生对象的个数

package com.djk.demo1;

public class MyCompent
{
	
}

package com.djk.demo1;

import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.*;
import static com.sun.btrace.BTraceUtils.*;
import com.sun.btrace.annotations.OnMethod;

@BTrace
public class MyCompentTrace 
{
	
	private static volatile long count;
	
	@OnMethod(
			clazz="com.djk.MyCompent",
			method="<init>"
			)
	
    public static void onCreate(@Self MyCompent c) 
	{
        // increment counter on constructor entry
        count++;
    }
	
	@OnTimer(2000)
    public static void toPrint() {
        println(Strings.strcat("MyCompent count = ", str(count)));
    }
}

这个MyCompentTrace 是看我的MyCompent类被实列化了几次.

2：计算一个方法运行的时间:

package com.djk.demo2;

public class MyTest2 {
	public static void main(String[] args) throws InterruptedException 
	{
		Thread.sleep(10000);
		MyTest2 a = new MyTest2();
		a.test();
	}
	
	public void test()
	{
		try
		{
			Thread.sleep(1000);
		} catch (Exception e) {
		}
	}
}

package com.djk.demo2;

import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.TLS;
import com.sun.btrace.annotations.*;
import static com.sun.btrace.BTraceUtils.*;

@BTrace
public class MyTest2Trace 
{
    @TLS
    private static long startTime = 0;  
    
	@OnMethod(
			clazz="com.djk.demo2.MyTest2",
			method="test"
			)
	
	public static void startTime()
	{
		startTime = timeMillis();
	}
	
    
	@OnMethod(
			clazz="com.djk.demo2.MyTest2",
			method="test",
			location=@Location(Kind.RETURN)
			)
	
	public static void endTime()
	{
	       println(strcat("the class method execute time=>", str(timeMillis()-startTime)));  
	        println("-------------------------------------------");  
	}
	
    @OnMethod(clazz = "com.djk.demo2.MyTest2", method = "test", location = @Location(Kind.RETURN))  
    public static void traceExecute(@ProbeClassName String name,@ProbeMethodName String method){  
        println(strcat("the class name=>", name));  
        println(strcat("the class method=>", method));  
          
    }  
	
}

3:跟踪一个方法的入参和出参：

package com.djk.demo3;

public class Clalbean 
{
	private int result=0;
	
	public int add(int i,int j)
	{
		result = i+j;
		return i+j;
	}
	
}

package com.djk.demo3;

import com.sun.btrace.annotations.*;

import static com.sun.btrace.BTraceUtils.*;

@BTrace
public class MyTest3Trace
{
	@TLS
	private static long startTime=0;
	
	   private static Object totalCount = 0;  
	
	@OnMethod(clazz="com.djk.demo3.Clalbean",method="add")
	public static void startTime()
	{
		startTime=timeMillis();
	}
	
	@OnMethod(clazz="com.djk.demo3.Clalbean",method="add",location=@Location(Kind.RETURN))
	public static void endTime()
	{
		println(strcat("the class method execute time=>", str(timeMillis()-startTime)));  
	}
	
	@OnMethod(clazz="com.djk.demo3.Clalbean",method="add",location=@Location(Kind.RETURN))
	public static void executeDetail(int i,int j,@Return int result)
	{
	     println("====== ");  
	     println(strcat("parameter num1:",str(i)));  
	     println(strcat("parameter num2:",str(j))); 
	     println(strcat("return value:",str(result)));  
	}
	@OnMethod(clazz="com.djk.demo3.Clalbean",method="add",location=@Location(Kind.RETURN))
	public static void executetest(@Self Clalbean c)
	{
		totalCount =  get(field("com.djk.demo3.Clalbean","result"), c);
	     println(strcat("fafda rea:",str(totalCount)));  
		
	}
	
}