不是抽象的，不重寫抽象方法錯誤

Question

我完全停留在我的班級顯示錯誤之一：

ResettableHttpServletResponse is not abstract and does not override abstract method getHeaderNames() in HttpServletResponse 

這裏是我的整個類：

import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.io.FileReader; 
import java.io.IOException; 
import java.io.OutputStream; 
import java.io.PrintWriter; 
import java.util.ArrayList; 
import java.util.HashSet; 
import java.util.List; 
import java.util.Locale; 
import java.util.Set; 

import javax.servlet.ServletOutputStream; 
import javax.servlet.http.Cookie; 
import javax.servlet.http.HttpServletResponse; 

import org.apache.commons.io.IOUtils; 
import org.apache.commons.lang.exception.NestableRuntimeException; 


@SuppressWarnings("deprecation") 
public class ResettableHttpServletResponse implements HttpServletResponse, Resettable { 

    private interface ResponseOperation { 

     void apply(); 
    } 
    private HttpServletResponse wrapped; 
    private List<ResponseOperation> operations; 
    private Locale locale; 
    private int bufferSize; 
    private String contentType; 
    private String charset; 
    private PrintWriter writer; 
    private OutputStream outputStream; 
    private ServletOutputStream servletOutputStream; 
    private File contents; 
    private Set<String> headerNames; 
    private int status; 
    private boolean stateApplied; 

    public ResettableHttpServletResponse(final HttpServletResponse response) { 
     wrapped = response; 
     operations = new ArrayList<ResponseOperation>(); 
     headerNames = new HashSet<String>(); 
     resetState(); 
    } 

    @Override 
    public void addCookie(final Cookie cookie) { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.addCookie(cookie); 
      } 
     }); 
    } 

    @Override 
    public void addDateHeader(final String name, final long date) { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.addDateHeader(name, date); 
      } 
     }); 
    } 

    @Override 
    public void addHeader(final String name, final String value) { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.addHeader(name, value); 
      } 
     }); 
    } 

    @Override 
    public void addIntHeader(final String name, final int value) { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.addIntHeader(name, value); 
      } 
     }); 
    } 

    @Override 
    public void applyState() { 
     try { 
      // Apply all operations 
      for (final ResponseOperation operation : operations) { 
       operation.apply(); 
      } 
      // Copy the response contents, if any 
      if (outputStream != null) { 
       try { 
        outputStream.flush(); 
        IOUtils.copy(new FileInputStream(contents), wrapped.getOutputStream()); 
       } catch (final Exception e) { 
        throw new NestableRuntimeException(e); 
       } 
      } else if (writer != null) { 
       try { 
        writer.flush(); 
        IOUtils.copy(new FileReader(contents), wrapped.getWriter()); 
       } catch (final Exception e) { 
        throw new NestableRuntimeException(e); 
       } 
      } 
      stateApplied = true; 
     } finally { 
      reset(); 
     } 
    } 

    @Override 
    public boolean containsHeader(final String name) { 
     return headerNames.contains(name); 
    } 

    @Override 
    public String encodeRedirectUrl(final String url) { 
     return wrapped.encodeRedirectUrl(url); 
    } 

    @Override 
    public String encodeRedirectURL(final String url) { 
     return wrapped.encodeRedirectURL(url); 
    } 

    @Override 
    public String encodeUrl(final String url) { 
     return wrapped.encodeUrl(url); 
    } 

    @Override 
    public String encodeURL(final String url) { 
     return wrapped.encodeURL(url); 
    } 

    @Override 
    public void flushBuffer() throws IOException { 
     // No-op, as nothing has been done in the real response 
    } 

    @Override 
    public int getBufferSize() { 
     return bufferSize; 
    } 

    @Override 
    public String getCharacterEncoding() { 
     return charset; 
    } 

    @Override 
    public String getContentType() { 
     return contentType; 
    } 

    @Override 
    public Locale getLocale() { 
     return locale; 
    } 

    @Override 
    public ServletOutputStream getOutputStream() throws IOException { 
     if (writer != null) { 
      throw new IllegalStateException("getWriter() was already invoked in this response"); 
     } 
     if (servletOutputStream == null) { 
      contents = File.createTempFile("cyclos_", "_response"); 
      outputStream = new FileOutputStream(contents); 
      servletOutputStream = new ServletOutputStream() { 
       @Override 
       public void close() throws IOException { 
        outputStream.close(); 
       } 

       @Override 
       public void flush() throws IOException { 
        outputStream.flush(); 
       } 

       @Override 
       public void write(final byte[] b) throws IOException { 
        outputStream.write(b); 
       } 

       @Override 
       public void write(final byte[] b, final int off, final int len) throws IOException { 
        outputStream.write(b, off, len); 
       } 

       @Override 
       public void write(final int b) throws IOException { 
        outputStream.write(b); 
       } 
      }; 
     } 
     return servletOutputStream; 
    } 

    public int getStatus() { 
     return status; 
    } 

    @Override 
    public PrintWriter getWriter() throws IOException { 
     if (outputStream != null) { 
      throw new IllegalStateException("getOutputStream() was already invoked"); 
     } 
     if (writer == null) { 
      contents = File.createTempFile("cyclos_", "_response"); 
      writer = new PrintWriter(contents); 
     } 
     return writer; 
    } 

    @Override 
    public boolean isCommitted() { 
     if (!stateApplied) { 
      return false; 
     } 
     return wrapped.isCommitted(); 
    } 

    @Override 
    public void reset() { 
     resetState(); 
    } 

    @Override 
    public void resetBuffer() { 
     IOUtils.closeQuietly(outputStream); 
     IOUtils.closeQuietly(writer); 
     outputStream = null; 
     servletOutputStream = null; 
     writer = null; 
     if (contents != null) { 
      contents.delete(); 
      contents = null; 
     } 
    } 

    @Override 
    public void resetState() { 
     status = 0; 
     operations.clear(); 
     headerNames.clear(); 
     charset = wrapped.getCharacterEncoding(); 
     bufferSize = wrapped.getBufferSize(); 
     contentType = wrapped.getContentType(); 
     locale = wrapped.getLocale(); 
     resetBuffer(); 
    } 

    @Override 
    public void sendError(final int sc) { 
     status = sc; 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       try { 
        wrapped.sendError(sc); 
       } catch (final IOException e) { 
        throw new NestableRuntimeException(e); 
       } 
      } 
     }); 
    } 

    @Override 
    public void sendError(final int sc, final String msg) throws IOException { 
     status = sc; 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       try { 
        wrapped.sendError(sc, msg); 
       } catch (final IOException e) { 
        throw new NestableRuntimeException(e); 
       } 
      } 
     }); 
    } 

    @Override 
    public void sendRedirect(final String location) throws IOException { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       try { 
        wrapped.sendRedirect(location); 
       } catch (final IOException e) { 
        throw new NestableRuntimeException(e); 
       } 
      } 
     }); 
    } 

    @Override 
    public void setBufferSize(final int bufferSize) { 
     this.bufferSize = bufferSize; 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setBufferSize(bufferSize); 
      } 
     }); 
    } 

    @Override 
    public void setCharacterEncoding(final String charset) { 
     this.charset = charset; 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setCharacterEncoding(charset); 
      } 
     }); 
    } 

    @Override 
    public void setContentLength(final int len) { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setContentLength(len); 
      } 
     }); 
    } 

    @Override 
    public void setContentType(final String contentType) { 
     this.contentType = contentType; 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setContentType(contentType); 
      } 
     }); 
    } 

    @Override 
    public void setDateHeader(final String name, final long date) { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setDateHeader(name, date); 
      } 
     }); 
    } 

    @Override 
    public void setHeader(final String name, final String value) { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setHeader(name, value); 
      } 
     }); 
    } 

    @Override 
    public void setIntHeader(final String name, final int value) { 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setIntHeader(name, value); 
      } 
     }); 
    } 

    @Override 
    public void setLocale(final Locale locale) { 
     this.locale = locale; 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setLocale(locale); 
      } 
     }); 
    } 

    @Override 
    public void setStatus(final int sc) { 
     status = sc; 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setStatus(sc); 
      } 
     }); 
    } 

    @Override 
    public void setStatus(final int sc, final String sm) { 
     status = sc; 
     operations.add(new ResponseOperation() { 
      @Override 
      public void apply() { 
       wrapped.setStatus(sc, sm); 
      } 
     }); 
    } 
} 

任何人告訴我我應該做些什麼來擺脫這個錯誤？

編輯：我在類中添加了下面的方法聲明，但它似乎並沒有影響我的錯誤。我該怎麼做？

@Override 
public Collection<String> getHeaderNames() { 
    operations.add(new ResponseOperation() { 
     @Override 
     public void apply() { 
      wrapped.getHeaderNames(); 
     } 
    }); 
    return headerNames; 
} 

Answer 1

當你實現一個類，這是不是抽象的接口，你必須重新定義接口中聲明的所有方法。在這裏，您並未重新定義界面HttpServletResponse中聲明的方法getHeaderNames()。

你需要重寫這個方法在你的類ResettableHttpServletResponse

編輯：

你得到的錯誤是明確的。它清楚地表明您忘記覆蓋界面HttpServletResponse的方法getHeaderNames。

您應該閱讀關於接口和繼承的lesson。

Answer 2

抽象類或接口（本例）HttpServletResponse定義了一個抽象方法getHeaderNames()，它沒有實現。由於你的班級不是抽象的，這是一個錯誤。通常IDE可以爲所有抽象方法生成一個虛擬實現。

您可以考慮使用HttpServletResponseWrapper來代替。