异常模板代码

看这篇文章：http://tutorials.jenkov.com/java-exception-handling/exception-handling-templates.html

再录一下：

一个异常捕获后，在 finally 里中再捕获异常，抛出异常会覆盖先前的异常信息，所以需要清晰的判断每个可能的异常，如此不会遗漏被覆盖的异常。如果代码复杂，异常判断是一键冗余的事情，所以会用模板的方式来简化工作，减少出错。

其实就是讲一个共通的代码如何更加优雅的公用。

 Input       input            = null;IOException processException = null;try{input = new FileInputStream(fileName);//...process input stream...} catch (IOException e) {processException = e;} finally {if(input != null){try {input.close();} catch(IOException e){if(processException != null){throw new MyException(processException, e,"Error message..." +fileName);} else {throw new MyException(e,"Error closing InputStream for file " +fileName;}}}if(processException != null){throw new MyException(processException,"Error processing InputStream for file " +fileName;}

 

模板模式：

public abstract class InputStreamProcessingTemplate {public void process(String fileName){IOException processException = null;InputStream input = null;try{input = new FileInputStream(fileName);doProcess(input);} catch (IOException e) {processException = e;} finally {if(input != null){try {input.close();} catch(IOException e){if(processException != null){throw new MyException(processException, e,"Error message..." +fileName);} else {throw new MyException(e,"Error closing InputStream for file " +fileName;}}}if(processException != null){throw new MyException(processException,"Error processing InputStream for file " +fileName;}}//override this method in a subclass, to process the stream.public abstract void doProcess(InputStream input) throws IOException;
}

调用：

  new InputStreamProcessingTemplate(){public void doProcess(InputStream input) throws IOException{int inChar = input.read();while(inChar !- -1){//do something with the chars...
            }}}.process("someFile.txt");

 

接口实现的办法：

public interface InputStreamProcessor {public void process(InputStream input) throws IOException;
}public class InputStreamProcessingTemplate {public void process(String fileName, InputStreamProcessor processor){IOException processException = null;InputStream input = null;try{input = new FileInputStream(fileName);processor.process(input);} catch (IOException e) {processException = e;} finally {if(input != null){try {input.close();} catch(IOException e){if(processException != null){throw new MyException(processException, e,"Error message..." +fileName;} else {throw new MyException(e,"Error closing InputStream for file " +fileName);}}}if(processException != null){throw new MyException(processException,"Error processing InputStream for file " +fileName;}}
}

调用：

new InputStreamProcessingTemplate().process("someFile.txt", new InputStreamProcessor(){public void process(InputStream input) throws IOException{int inChar = input.read();while(inChar !- -1){//do something with the chars...
                }}});

 

静态模板：

public class InputStreamProcessingTemplate {public static void process(String fileName,InputStreamProcessor processor){IOException processException = null;InputStream input = null;try{input = new FileInputStream(fileName);processor.process(input);} catch (IOException e) {processException = e;} finally {if(input != null){try {input.close();} catch(IOException e){if(processException != null){throw new MyException(processException, e,"Error message..." +fileName);} else {throw new MyException(e,"Error closing InputStream for file " +fileName;}}}if(processException != null){throw new MyException(processException,"Error processing InputStream for file " +fileName;}}
}

 

调用：

 InputStreamProcessingTemplate.process("someFile.txt",new InputStreamProcessor(){public void process(InputStream input) throws IOException{int inChar = input.read();while(inChar !- -1){//do something with the chars...
                }}});