java异常链处理

jdk1.4后的，所有异常根类Throwable部分代码

    /** 描述异常的信息 */
    private String detailMessage;

    /** 本异常包裹的原因异常，默认状态下，cause指向本异常 */
    private Throwable cause = this;

    /** 在构造函数初始化异常的细节信息 */
    public Throwable(String message, Throwable cause) {
        fillInStackTrace();
        detailMessage = message;
        this.cause = cause;
    }

    public Throwable(Throwable cause) {
    	// 将当前线程的堆栈内容记录在本异常的追踪信息中
        fillInStackTrace();
        // 记录本异常的细节信息，如果cause为null，则detailMessage为null，否则为cause.toString()
        detailMessage = (cause==null ? null : cause.toString());
        // 记录异常原因
        this.cause = cause;
    }
    
    public Throwable(Throwable cause, String message) {
    	// 将当前线程的堆栈内容记录在本异常的追踪信息中
        fillInStackTrace();
        // 记录本异常的细节信息
        detailMessage = message;
        // 记录异常原因
        this.cause = cause;
    }

    /** 获得原因异常，如果cause指向本异常，说明原因异常不存在或未知，返回null */
    public Throwable getCause() {
        return (cause==this ? null : cause);
    }

    /** 初始化原因异常，此方法最多调用一次 */
    public synchronized Throwable initCause(Throwable cause) {
    	// 如果原因异常不指向本异常，即原因异常已经存在，抛出异常：说明不能覆盖
        if (this.cause != this)
            throw new IllegalStateException("Can't overwrite cause");
        // 如果输入参数cause指向本异常，抛出异常：不可以把自身作为原因异常
        if (cause == this)
            throw new IllegalArgumentException("Self-causation not permitted");
        // 记录原因异常
        this.cause = cause;
        return this;
    }


    /** 原生方法，将当前线程的堆栈内容记录在本异常的追踪信息中 */
    public synchronized native Throwable fillInStackTrace();

关于异常链的一个例子

class HighLevelException extends Exception{
	public HighLevelException(Throwable cause) {
		super(cause);
	}
}

class MiddleLevelException extends Exception{
	public MiddleLevelException(Throwable cause) {
		super(cause);
	}
}

class LowLevelException extends Exception{
}

public class TestException {

	public void highLevelAccess() throws HighLevelException{
		try {
			middleLevelAccess();
		} catch (Exception e) {
			throw new HighLevelException(e);
		}
	}
	
	public void middleLevelAccess() throws MiddleLevelException{
		try {
			lowLevelAccess();
		} catch (Exception e) {
			throw new MiddleLevelException(e);
		}
	}

	public void lowLevelAccess() throws LowLevelException {
		throw new LowLevelException();
	}

	public static void main(String[] args) {
		try {
			new TestException().highLevelAccess();
		} catch (HighLevelException e) {
			e.printStackTrace();
		}
	}
}

错误信息

test.HighLevelException: test.MiddleLevelException: test.LowLevelException
	at test.TestException.highLevelAccess(TestException.java:24)
	at test.TestException.main(TestException.java:42)
Caused by: test.MiddleLevelException: test.LowLevelException
	at test.TestException.middleLevelAccess(TestException.java:32)
	at test.TestException.highLevelAccess(TestException.java:22)
	... 1 more
Caused by: test.LowLevelException
	at test.TestException.lowLevelAccess(TestException.java:37)
	at test.TestException.middleLevelAccess(TestException.java:30)
	... 2 more