【java】Execption的 e.getMessage()为null的解决方法

================================

场景：

　　当代码出现异常时通常都需要将异常信息写入到日志中，异常信息越详细越有利于问题的排查。而通过的Exception.getMessage()方法只能获得异常的名称而不能获取哪里出现的异常，对于排错意义不大。

甚至有时候，getMessage()返回的是null。

查看getMessage()的源码：

/**
     * Returns the detail message string of this throwable.
     *
     * @return  the detail message string of this {@code Throwable} instance
     *          (which may be {@code null}).
     */
    public String getMessage() {
        return detailMessage;
    }

可以看到说明，与可能返回为null。

解决方法：

罗列四个解决方法

//1、
public String getTrace(Throwable t) {
    StringWriter stringWriter= new StringWriter();
    PrintWriter writer= new PrintWriter(stringWriter);
    t.printStackTrace(writer);
    StringBuffer buffer= stringWriter.getBuffer();
    return buffer.toString();
}
 
//2、
public static String getExceptionAllinformation(Exception ex){
        String sOut = "";
        StackTraceElement[] trace = ex.getStackTrace();
        for (StackTraceElement s : trace) {
            sOut += "	at " + s + "
";
        }
        return sOut;
}
 
//3、
public static String getExceptionAllinformation_01(Exception ex) {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        PrintStream pout = new PrintStream(out);
        ex.printStackTrace(pout);
        String ret = new String(out.toByteArray());
        pout.close();
        try {
             out.close();
        } catch (Exception e) {
        }
        return ret;
}
 
//4、
private static String toString_02(Throwable e){  
         StringWriter sw = new StringWriter();  
         PrintWriter pw = new PrintWriter(sw, true);  
         e.printStackTrace(pw);  
         pw.flush();   
         sw.flush();  
         return sw.toString(); 
} 

具体使用场景：

　　　　　　　　　　try {
                   .....

                }catch (Exception e){
                    StringWriter stringWriter= new StringWriter();
                    PrintWriter writer= new PrintWriter(stringWriter);
                    e.printStackTrace(writer);
                    StringBuffer buffer= stringWriter.getBuffer();
                    String errMsg = buffer.toString();

                    logger.error(errMsg);

                    hashMap.put("status",String.valueOf(-1));
                    hashMap.put("errorMsg",StringUtils.isBlank(errMsg) ? "" : errMsg);
                }finally {
                    redisUtil.HASH.hmset(recordKey,hashMap);
                    String lpop = redisUtil.LISTS.lpop(runTaskKey);
                    System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>任务执行完成，执行队列"+runTaskKey+"移除："+lpop);
                    hashMap.clear();
                }

参考地址：

https://blog.csdn.net/wjiaoling136/article/details/84903619