java 在线找bug 神器 btrace

示例地址 ： http://kenai.com/projects/btrace/sources/hg/show/samples
1. 示例代码

示例代码定义了Counter计数器，有一个add()方法，每次增加随机值，总数保存在totalCount属性中。

Btracetest.java代码


package com.learnworld;
import java.util.Random;

public class BTraceTest {

public static void main(String[] args) throws Exception {
Random random = new Random();

// 计数器
Counter counter = new Counter();
while (true) {
// 每次增加随机值
counter.add(random.nextInt(10));
Thread.sleep(1000);
}
}
}

Counter.java代码


package com.learnworld;
public class Counter {
// 总数
private static int totalCount = 0;

public int add(int num) throws Exception {
totalCount += num;
sleep();
return totalCount;
}

public void sleep() throws Exception {
Thread.sleep(1000);
}

}

2. 常见使用场景

下面通过几个常见使用场景演示如何使用BTrace脚本。

1) 获取add()方法参数值和返回值。

Java代码


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

@BTrace
public class TracingScript {
@OnMethod(
clazz="com.learnworld.Counter",
method="add",
location=@Location(Kind.RETURN)
)
public static void traceExecute(int num,@Return int result){
println("====== ");
println(strcat("parameter num: ",str(num)));
println(strcat("return value:",str(result)));
}
}

2) 定时获取Counter类的属性值totalCount。

Java代码


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

@BTrace
public class TracingScript {
private static Object totalCount = 0;

@OnMethod(
clazz="com.learnworld.Counter",
method="add",
location=@Location(Kind.RETURN)
)
public static void traceExecute(@Self com.learnworld.Counter counter){
totalCount = get(field("com.learnworld.Counter","totalCount"), counter);
}

@OnTimer(1000)
public static void print(){
println("====== ");
println(strcat("totalCount: ",str(totalCount)));
}
}

3) 获取add方法执行时间。

Java代码


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

@BTrace
public class TracingScript {
@TLS private static long startTime = 0;

@OnMethod(
clazz="com.learnworld.Counter",
method="add"
)
public static void startExecute(){
startTime = timeNanos();
}

@OnMethod(
clazz="com.learnworld.Counter",
method="add",
location=@Location(Kind.RETURN)
)
public static void endExecute(@Duration long duration){
long time = timeNanos() - startTime;
println(strcat("execute time(nanos): ", str(time)));
println(strcat("duration(nanos): ", str(duration)));
}
}

4) 获取add()方法调用方法sleep()次数。

Java代码


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

@BTrace
public class TracingScript {
private static long count;

@OnMethod(
clazz="/.*/",
method="add",
location=@Location(value=Kind.CALL, clazz="/.*/", method="sleep")
)
public static void traceExecute(@ProbeClassName String pcm, @ProbeMethodName String pmn,
@TargetInstance Object instance, @TargetMethodOrField String method){
println("====== ");
println(strcat("ProbeClassName: ",pcm));
println(strcat("ProbeMethodName: ",pmn));
println(strcat("TargetInstance: ",str(classOf(instance))));
println(strcat("TargetMethodOrField : ",str(method)));
count++;
}

@OnEvent
public static void getCount(){
println(strcat("count: ", str(count)));
}
}