Java中处理Exception.md

Java中的异常处理

在Finally块中清理资源或者使用try-with-resource语句

public void automaticallyCloseResource(){
    File file = new File("./tmp.txt");
    
    try(FileInputStream is = new FileInputStream(file);){
        is.read();
    }catch(FileNotFoundException e){
        log.error(e);
    }catch(IOException e){
        log.error(e);
    }
}

指定具体的异常

//这种使用毫无意义
public void doNotDoThis() throws Exception{}

//指定具体的异常
public void doThis() throws NumberFormatException{}

对异常进行文档说明

/**
 *	This method does something extremely useful...
 *
 *	@param input
 *	@throws MyBussinessException if ... happens
 */
public void doSomething(String input) throws MyBussinessException{}

抛出异常的时候包含描述信息

try{
    new Long("xyz");
}catch(NumberFormatException e){
    log.error(e);
}

首先捕获最具体的异常

public void catchMostSpecificExceptionFirst(){
    try{
        doSomething("A message");
    }catch(NumberFormatException e){
        log.error(e);
    }catch(IllegalArgumentException e){
        log.error(e);
    }
}

不要捕获Throwable

public void doNotCatchThrowable(){
    try{
        
    }catch(Throwable t){
        //never do this
    }
}

不要忽略异常(一定要打印异常)

public void doNotIgnoreExceptions(){
    try{
        
    }catch(NumberFormatException e){
        log.error("This should never happen :" + e);
    }
}

不要记录并抛出异常

try{
    new Long("xyz");
}catch(NumberFormatException e){
    log.error(e);
    //throw e;	//do not do this
}

包装自定义异常(包装异常时不要抛弃原始的异常)

public void wrapException(String input) throws MyBusinessException {
    try{
        
    }catch(NumberFormatException e){
        throw new MyBusinessException("A message that describes the error.",e);
    }
}