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... } } });