javaee-HttpServletResponse 类相关源代码

ServletAPI 2.5的源代码

1.ServletResponse类的源代码如下：

package javax.servlet;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Locale;

public abstract interface ServletResponse
{
  public abstract String getCharacterEncoding();

  public abstract String getContentType();

  public abstract ServletOutputStream getOutputStream()
    throws IOException;

  public abstract PrintWriter getWriter()
    throws IOException;

  public abstract void setCharacterEncoding(String paramString);

  public abstract void setContentLength(int paramInt);

  public abstract void setContentType(String paramString);

  public abstract void setBufferSize(int paramInt);

  public abstract int getBufferSize();

  public abstract void flushBuffer()
    throws IOException;

  public abstract void resetBuffer();

  public abstract boolean isCommitted();

  public abstract void reset();

  public abstract void setLocale(Locale paramLocale);

  public abstract Locale getLocale();
}

 

2.HttpServletResponse 类的源代码如下：

package javax.servlet.http;

import java.io.IOException;
import javax.servlet.ServletResponse;

public abstract interface HttpServletResponse extends ServletResponse
{
  public static final int SC_CONTINUE = 100;//SC是 status code的简写
  public static final int SC_SWITCHING_PROTOCOLS = 101;
  public static final int SC_OK = 200;
  public static final int SC_CREATED = 201;
  public static final int SC_ACCEPTED = 202;
  public static final int SC_NON_AUTHORITATIVE_INFORMATION = 203;
  public static final int SC_NO_CONTENT = 204;
  public static final int SC_RESET_CONTENT = 205;
  public static final int SC_PARTIAL_CONTENT = 206;
  public static final int SC_MULTIPLE_CHOICES = 300;
  public static final int SC_MOVED_PERMANENTLY = 301;
  public static final int SC_MOVED_TEMPORARILY = 302;
  public static final int SC_FOUND = 302;
  public static final int SC_SEE_OTHER = 303;
  public static final int SC_NOT_MODIFIED = 304;
  public static final int SC_USE_PROXY = 305;
  public static final int SC_TEMPORARY_REDIRECT = 307;
  public static final int SC_BAD_REQUEST = 400;
  public static final int SC_UNAUTHORIZED = 401;
  public static final int SC_PAYMENT_REQUIRED = 402;
  public static final int SC_FORBIDDEN = 403;
  public static final int SC_NOT_FOUND = 404;
  public static final int SC_METHOD_NOT_ALLOWED = 405;
  public static final int SC_NOT_ACCEPTABLE = 406;
  public static final int SC_PROXY_AUTHENTICATION_REQUIRED = 407;
  public static final int SC_REQUEST_TIMEOUT = 408;
  public static final int SC_CONFLICT = 409;
  public static final int SC_GONE = 410;
  public static final int SC_LENGTH_REQUIRED = 411;
  public static final int SC_PRECONDITION_FAILED = 412;
  public static final int SC_REQUEST_ENTITY_TOO_LARGE = 413;
  public static final int SC_REQUEST_URI_TOO_LONG = 414;
  public static final int SC_UNSUPPORTED_MEDIA_TYPE = 415;
  public static final int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
  public static final int SC_EXPECTATION_FAILED = 417;
  public static final int SC_INTERNAL_SERVER_ERROR = 500;
  public static final int SC_NOT_IMPLEMENTED = 501;
  public static final int SC_BAD_GATEWAY = 502;
  public static final int SC_SERVICE_UNAVAILABLE = 503;
  public static final int SC_GATEWAY_TIMEOUT = 504;
  public static final int SC_HTTP_VERSION_NOT_SUPPORTED = 505;

  public abstract void addCookie(Cookie paramCookie);

  public abstract boolean containsHeader(String paramString);

  public abstract String encodeURL(String paramString);

  public abstract String encodeRedirectURL(String paramString);

  /**
   * @deprecated
   */
  public abstract String encodeUrl(String paramString);

  /**
   * @deprecated
   */
  public abstract String encodeRedirectUrl(String paramString);

  public abstract void sendError(int paramInt, String paramString)
    throws IOException;

  public abstract void sendError(int paramInt)
    throws IOException;

  public abstract void sendRedirect(String paramString)
    throws IOException;

  public abstract void setDateHeader(String paramString, long paramLong);

  public abstract void addDateHeader(String paramString, long paramLong);

  public abstract void setHeader(String paramString1, String paramString2);

  public abstract void addHeader(String paramString1, String paramString2);

  public abstract void setIntHeader(String paramString, int paramInt);

  public abstract void addIntHeader(String paramString, int paramInt);

  public abstract void setStatus(int paramInt);

  /**
   * @deprecated
   */
  public abstract void setStatus(int paramInt, String paramString);
}

 

2.1HttpServletResponse 对象所想描述的结构如下（http响应格式图）：

 

 

其中，消息头，可以通过“meta ”标签equiv属性来模拟，如下

 

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
……

 

但是其优先级没有相应头高。

 

 

 

另外，如果页面本身编码为utf-8，浏览器将会识别出来，并强制设置为utf-8编码。"Content-Type""将不起作用。

 

 

3.ServletOutputStream和PrintWriter

 

ServletResponse类提供了如下两个方法：

 

 

public abstract ServletOutputStream getOutputStream()
    throws IOException;

  public abstract PrintWriter getWriter()
    throws IOException;

 

 

 

 

      Servlet程序向ServletOutputStream或PrintWriter对象中写入的数据将被Servlet引擎获取，Servlet引擎，将这些数据当作响应消息的正文，然后再与响应状态行，响应头组合输出到客户端（通常为IE，Chrome等浏览器）。

 

       ServletOutputStream主要针对字节，而PrintWriter针对字符串。另外getOutputStream和getWriter在一个service方法中不能同时调用。

 

参考：《深入体验Java_Web开发内幕-核心基础\》