omcat5下jsp出现getOutputStream() has already been called for this response异常的原因和解决方法

    技术2022-05-12  0

    【标  题】:tomcat5下jsp出现getOutputStream() has already been called for this response异常的原因和解决方法【关键字】:tomcat5,jsp,getOutputStream,has,already,been,called,for,this,response【来  源】:http://blog.csdn.net/alexwan/archive/2007/02/13/1508871.aspx

     

    tomcat5下jsp出现getOutputStream() has already been called for this response异常的原因和解决方法

    在tomcat5下jsp中出现此错误一般都是在jsp中使用了输出流(如输出图片验证码,文件下载等),没有妥善处理好的原因。具体的原因就是在tomcat中jsp编译成servlet之后在函数_jspService(HttpServletRequest request, HttpServletResponse response)的最后有一段这样的代码finally {      if (_jspxFactory != null) _jspxFactory.releasePageContext(_jspx_page_context);    }这里是在释放在jsp中使用的对象,会调用response.getWriter(),因为这个方法是和response.getOutputStream()相冲突的!所以会出现以上这个异常。

    然后当然是要提出解决的办法,其实挺简单的(并不是和某些朋友说的那样--将jsp内的所有空格和回车符号所有都删除掉),

    在使用完输出流以后调用以下两行代码即可:out.clear();out = pageContext.pushBody();

    最后这里是一个输出彩色验证码例子(这样的例子几乎随处可见)imag.jsp

     

    <% @ page   import = " java.awt.*,java.awt.image.*,java.util.*,javax.imageio.* "   %> <% @ page  import = " java.io.OutputStream "   %> <%! Color getRandColor( int  fc, int  bc){Random random  =   new  Random(); if (fc > 255 ) fc = 255 ; if (bc > 255 ) bc = 255 ; int  r = fc + random.nextInt(bc - fc); int  g = fc + random.nextInt(bc - fc); int  b = fc + random.nextInt(bc - fc); return   new  Color(r,g,b);} %> <% try {response.setHeader( " Pragma " , " No-cache " );response.setHeader( " Cache-Control " , " no-cache " );response.setDateHeader( " Expires " 0 ); int  width = 60 , height = 20 ;BufferedImage image  =   new  BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);OutputStream os = response.getOutputStream();Graphics g  =  image.getGraphics();Random random  =   new  Random();g.setColor(getRandColor( 200 , 250 ));g.fillRect( 0 0 , width, height);g.setFont( new  Font( " Times New Roman " ,Font.PLAIN, 18 ));g.setColor(getRandColor( 160 , 200 )); for  ( int  i = 0 ;i < 155 ;i ++ ){ int  x  =  random.nextInt(width); int  y  =  random.nextInt(height); int  xl  =  random.nextInt( 12 ); int  yl  =  random.nextInt( 12 );g.drawLine(x,y,x + xl,y + yl);}String sRand = "" ; for  ( int  i = 0 ;i < 4 ;i ++ ){String rand = String.valueOf(random.nextInt( 10 ));sRand += rand;g.setColor( new  Color( 20 + random.nextInt( 110 ), 20 + random.nextInt( 110 ), 20 + random.nextInt( 110 )));g.drawString(rand, 13 * i + 6 , 16 );}session.setAttribute( " rand " ,sRand);g.dispose();ImageIO.write(image,  " JPEG " ,os);os.flush();os.close();os = null ;response.flushBuffer();out.clear();out  =  pageContext.pushBody();} catch (IllegalStateException e){System.out.println(e.getMessage());e.printStackTrace();} %>

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