一种系统异常设计思路

来源：互联网发布：使用u盘安装ubuntu 编辑：程序博客网时间：2024/04/30 16:18

http://northconcepts.com/blog/2013/01/18/6-tips-to-improve-your-exception-handling/

1 系统只有一个异常基类继承RuntimeEcption，如果仅仅依靠异常子类的种类来区分，很容易造成类爆炸。

2 设置错误code，用枚举来保存，这样来区分异常类别，而且非常方便进行处理和国际化。

3 增加异常时参数设置，debug很容易找到当时的环境。

4 重写异常方法，抛出异常时打印出code和环境参数

5 正确包装其他异常，不用默认构造函数包装，防止异常无意义的嵌套。

package com.northconcepts.exception;import java.io.PrintStream;import java.io.PrintWriter;import java.util.Map;import java.util.TreeMap;public class SystemException extends RuntimeException {    private static final long serialVersionUID = 1L;    public static SystemException wrap(Throwable exception, ErrorCode errorCode) {        if (exception instanceof SystemException) {            SystemException se = (SystemException)exception;        if (errorCode != null && errorCode != se.getErrorCode()) {                return new SystemException(exception.getMessage(), exception, errorCode);}return se;        } else {            return new SystemException(exception.getMessage(), exception, errorCode);        }    }        public static SystemException wrap(Throwable exception) {    return wrap(exception, null);    }        private ErrorCode errorCode;    private final Map<String,Object> properties = new TreeMap<String,Object>();        public SystemException(ErrorCode errorCode) {this.errorCode = errorCode;}public SystemException(String message, ErrorCode errorCode) {super(message);this.errorCode = errorCode;}public SystemException(Throwable cause, ErrorCode errorCode) {super(cause);this.errorCode = errorCode;}public SystemException(String message, Throwable cause, ErrorCode errorCode) {super(message, cause);this.errorCode = errorCode;}public ErrorCode getErrorCode() {        return errorCode;    }public SystemException setErrorCode(ErrorCode errorCode) {        this.errorCode = errorCode;        return this;    }public Map<String, Object> getProperties() {return properties;}    @SuppressWarnings("unchecked")public <T> T get(String name) {        return (T)properties.get(name);    }    public SystemException set(String name, Object value) {        properties.put(name, value);        return this;    }        //重写Runtime方法。这里打印虚拟机错误信息，注意PrintStream要同步，不然异常并非时会乱掉    public void printStackTrace(PrintStream s) {        synchronized (s) {            printStackTrace(new PrintWriter(s));        }    }    //把出异常时的参数也 打印出来，方便调试    public void printStackTrace(PrintWriter s) {         synchronized (s) {            s.println(this);            s.println("\t-------------------------------");            if (errorCode != null) {        s.println("\t" + errorCode + ":" + errorCode.getClass().getName()); }            for (String key : properties.keySet()) {            s.println("\t" + key + "=[" + properties.get(key) + "]");             }            s.println("\t-------------------------------");            StackTraceElement[] trace = getStackTrace();            for (int i=0; i < trace.length; i++)                s.println("\tat " + trace[i]);            Throwable ourCause = getCause();            if (ourCause != null) {                ourCause.printStackTrace(s);            }            s.flush();        }    }    }

public class SystemExceptionExample2 {private static final int MIN_LENGTH = 10;public static void main(String[] args) {validate("email", "abc");}public static void validate(String field, String value) {if (value == null || value.length() < MIN_LENGTH) {throw new SystemException("发生错误！",ValidationCode.VALUE_TOO_SHORT).set("field", field).set("value", value).set("min-length", MIN_LENGTH); }}}

  public static void main(String[] args) {        System.out.println(getUserText(ValidationCode.VALUE_TOO_SHORT));    }        public static String getUserText(ErrorCode errorCode) {        if (errorCode == null) {            return null;        }        String key = errorCode.getClass().getSimpleName() + "__" + errorCode;        ResourceBundle bundle = ResourceBundle.getBundle("com.northconcepts.exception.example.exceptions");        return bundle.getString(key);    }

包装异常

catch (IOException e) {
throw SystemException.wrap(e,PaymentCode.CREDIT_CARD_EXPIRED).set("fileName", "aaa");