详谈Java 异常处理的误区和经验总结(分享)

<strong>package</strong> com.ibm.dw.sample.exception;
/**
 * 自定义 RuntimeException
 * 添加错误代码属性
 */
<strong>public</strong> <strong>class</strong> <strong>RuntimeException</strong> <strong>extends</strong> <strong>java</strong>.<strong>lang</strong>.<strong>RuntimeException</strong> { 
  //默认错误代码 
 <strong>public</strong> <strong>static</strong> <strong>final</strong> Integer GENERIC = 1000000; 
 //错误代码
 <strong>private</strong> Integer errorCode; 
  <strong>public</strong> <strong>RuntimeException</strong>(Integer errorCode,Throwable cause) {
   <strong>this</strong>(errorCode,<strong>null</strong>,cause);
  }
  <strong>public</strong> <strong>RuntimeException</strong>(String message,Throwable cause) {
   //利用通用错误代码
   <strong>this</strong>(GENERIC,message,cause);
  }
  <strong>public</strong> <strong>RuntimeException</strong>(Integer errorCode,String message,Throwable cause) {
   <strong>super</strong>(message,cause);
   <strong>this</strong>.errorCode = errorCode;
  }
  <strong>public</strong> Integer <strong>getErrorCode</strong>() {
   <strong>return</strong> errorCode;
  } 
}

<strong>public</strong> Customer <strong>retrieveCustomerById</strong>(Long id) <strong>throw</strong> SQLException {
 //根据 ID 查询数据库
}

<strong>public</strong> Customer <strong>retrieveCustomerById</strong>(Long id) {
  <strong>try</strong>{
   //根据 ID 查询数据库
  }<strong>catch</strong>(SQLException e){
   //利用非检测异常封装检测异常，降低层次耦合
   <strong>throw</strong> <strong>new</strong> RuntimeException(SQLErrorCode,e);
  }<strong>finally</strong>{
   //关闭连接，清理资源
  }
}

<strong>public</strong> <strong>void</strong> <strong>retrieveObjectById</strong>(Long id){
 <strong>try</strong>{
  //..some code that throws SQLException
 }<strong>catch</strong>(SQLException ex){
  /**
  *了解的人都知道，这里的异常打印毫无意义，仅仅是将错误堆栈输出到控制台。
  * 而在 Production 环境中，需要将错误堆栈输出到日志。
  * 而且这里 catch 处理之后程序继续执行，会导致进一步的问题*/
   ex.printStacktrace();
  }
}

<strong>public</strong> <strong>void</strong> <strong>retrieveObjectById</strong>(Long id){
 <strong>try</strong>{
 //..some code that throws SQLException
 }
 <strong>catch</strong>(SQLException ex){
 <strong>throw</strong> <strong>new</strong> RuntimeException(“Exception <strong>in</strong> retieveObjectById”,ex);
 }
 <strong>finally</strong>{
 //clean up resultset,statement,connection etc
 }
}

<strong>for</strong>(<strong>int</strong> i=0; i<100; i++){
 <strong>try</strong>{
 }<strong>catch</strong>(XXXException e){
   //….
 }
}

<strong>public</strong> <strong>void</strong> <strong>retrieveObjectById</strong>(Long id){
 <strong>try</strong>{
  //…抛出 IOException 的代码调用
  //…抛出 SQLException 的代码调用
 }<strong>catch</strong>(Exception e){
  //这里利用基类 Exception 捕捉的所有潜在的异常，如果多个层次这样捕捉，会丢失原始异常的有效信息
  <strong>throw</strong> <strong>new</strong> RuntimeException(“Exception <strong>in</strong> retieveObjectById”,e);
 }
}

<strong>public</strong> <strong>void</strong> <strong>retrieveObjectById</strong>(Long id){
 <strong>try</strong>{
  //..some code that throws RuntimeException,IOException,SQLException
 }<strong>catch</strong>(IOException e){
  //仅仅捕捉 IOException
  <strong>throw</strong> <strong>new</strong> RuntimeException(/*指定这里 IOException 对应的错误代码*/code,“Exception <strong>in</strong> retieveObjectById”,e);
 }<strong>catch</strong>(SQLException e){
  //仅仅捕捉 SQLException
  <strong>throw</strong> <strong>new</strong> RuntimeException(/*指定这里 SQLException 对应的错误代码*/code,e);
 }
}

<strong>try</strong>{
 //可能抛出 RuntimeException、IOExeption 或者其它；
 //注意这里和误区六的区别，这里是一段代码抛出多种异常。以上是多段代码，各自抛出不同的异常
}<strong>catch</strong>(<strong>Exception</strong> e){
 //一如既往的将 Exception 转换成 RuntimeException，但是这里的 e 其实是 RuntimeException 的实例，已经在前段代码中封装过
 <strong>throw</strong> <strong>new</strong> RuntimeException(/**/code,/**/,e);
}

<strong>public</strong> <strong>class</strong> <strong>A</strong> {
 <strong>private</strong> <strong>static</strong> Logger logger = LoggerFactory.getLogger(A.class);
 <strong>public</strong> <strong>void</strong> <strong>process</strong>(){
  <strong>try</strong>{
  //实例化 B 类，可以换成其它注入等方式
  B b = <strong>new</strong> B();
  b.process();
  //other code might cause exception
 } <strong>catch</strong>(XXXException e){
  //如果 B 类 process 方法抛出异常，异常会在 B 类中被打印，在这里也会被打印，从而会打印 2 次
  logger.error(e);
  <strong>throw</strong> <strong>new</strong> RuntimeException(/* 错误代码 */ errorCode,/*异常信息*/msg,e);
  }
 }
}
<strong>public</strong> <strong>class</strong> <strong>B</strong>{
 <strong>private</strong> <strong>static</strong> Logger logger = LoggerFactory.getLogger(B.class);
 <strong>public</strong> <strong>void</strong> <strong>process</strong>(){
  <strong>try</strong>{
   //可能抛出异常的代码
  }
  <strong>catch</strong>(XXXException e){
   logger.error(e);
   <strong>throw</strong> <strong>new</strong> RuntimeException(/* 错误代码 */ errorCode,e);
  }
 }
}

public <strong>void</strong> retieveObjectById(Long id){
 <strong>try</strong>{
  //..some code that throws SQLException
 }<strong>catch</strong>(SQLException ex){
  //将参数信息添加到异常信息中
  <strong>throw</strong> <strong>new</strong> RuntimeException(“Exception <strong>in</strong> retieveObjectById <strong>with</strong> Object Id :”+ id,ex);
 }
}