Examples of javax.servlet.jsp.JspWriter

javax.servlet.jsp.JspWriter
The actions and template data in a JSP page is written using the JspWriter object that is referenced by the implicit variable out which is initialized automatically using methods in the PageContext object.
This abstract class emulates some of the functionality found in the java.io.BufferedWriter and java.io.PrintWriter classes, however it differs in that it throws java.io.IOException from the print methods while PrintWriter does not.
Buffering
The initial JspWriter object is associated with the PrintWriter object of the ServletResponse in a way that depends on whether the page is or is not buffered. If the page is not buffered, output written to this JspWriter object will be written through to the PrintWriter directly, which will be created if necessary by invoking the getWriter() method on the response object. But if the page is buffered, the PrintWriter object will not be created until the buffer is flushed and operations like setContentType() are legal. Since this flexibility simplifies programming substantially, buffering is the default for JSP pages.
Buffering raises the issue of what to do when the buffer is exceeded. Two approaches can be taken:
- Exceeding the buffer is not a fatal error; when the buffer is exceeded, just flush the output.
- Exceeding the buffer is a fatal error; when the buffer is exceeded, raise an exception.
Both approaches are valid, and thus both are supported in the JSP technology. The behavior of a page is controlled by the autoFlush attribute, which defaults to true. In general, JSP pages that need to be sure that correct and complete data has been sent to their client may want to set autoFlush to false, with a typical case being that where the client is an application itself. On the other hand, JSP pages that send data that is meaningful even when partially constructed may want to set autoFlush to true; such as when the data is sent for immediate display through a browser. Each application will need to consider their specific needs.
An alternative considered was to make the buffer size unbounded; but, this had the disadvantage that runaway computations would consume an unbounded amount of resources.
The "out" implicit variable of a JSP implementation class is of this type. If the page directive selects autoflush="true" then all the I/O operations on this class shall automatically flush the contents of the buffer if an overflow condition would result if the current operation were performed without a flush. If autoflush="false" then all the I/O operations on this class shall throw an IOException if performing the current operation would result in a buffer overflow condition. @see java.io.Writer @see java.io.BufferedWriter @see java.io.PrintWriter

    public int doEndTag() {
        try {
            BodyContent body = getBodyContent();


            if (body != null) {
                JspWriter out = body.getEnclosingWriter();
                String bodyString = body.getString();
                body.clearBody();
                //Debug.logInfo("printing string: " + bodyString, module);
                out.print(bodyString);
            }
        } catch (IOException e) {
            Debug.logError(e, "IfTag Error.", module);
        }
        return EVAL_PAGE;

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        else
        {
            buffer.append(TagsSupport.getContextRelativeURL(pageContext,src,true));
        }
        buffer.append("\"/></script>");
        JspWriter writer = pageContext.getOut();
        try
        {
            writer.print(buffer.toString());
        } catch (IOException e)
        {
            throw new JspException(e);
        }
        return (SKIP_BODY);

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            else {                
                out = new JspWriterAdapter(out);
                pageContext.pushWriter((JspWriter)out);
                usesAdapter = true;
            }
            JspWriter w = new TagWriter(out, tag, pageContext, usesAdapter);
            pageContext.pushTopTag(tag);
            pageContext.pushWriter(w);
            return w;
        }
        catch(TemplateModelException e) {

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        else
        {
            buffer.append(TagsSupport.getContextRelativeURL(pageContext,src,true));
        }
        buffer.append("\"/></script>");
        JspWriter writer = pageContext.getOut();
        try
        {
            writer.print(buffer.toString());
        } catch (IOException e)
        {
            throw new JspException(e);
        }
        return (SKIP_BODY);

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            RenderResponse response = (RenderResponse) 
                pageContext.getRequest().getAttribute("javax.portlet.response");
            
            if (request == null || response == null)
            {
                JspWriter out = pageContext.getOut();
                out.print("request response not found");
                return SKIP_BODY;
            }
            PortletApplicationModel model = (PortletApplicationModel)request.getAttribute(FrameworkConstants.MODEL_TOOL);
            if (model == null)
            {
                JspWriter out = pageContext.getOut();
                out.print("model not found");
                return SKIP_BODY;
            }
                                                
            Forwarder forwarder = new Forwarder(model, request, response);
            if (view != null)
            {
                content = forwarder.getView(view).toString();
            }
            else if (forward != null)
            {
                if (action != null)
                {
                    content = forwarder.getLink(forward, action).toString();
                }
                else
                {
                    content = forwarder.getLink(forward).toString();                    
                }
            }
            else
            {
                content = forwarder.toString();
            }
            JspWriter out = pageContext.getOut();
            out.print(content);            
        }
        catch (IOException e)
        {
            System.err.println("Error printing tag: " + e);
        }

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     *
     * @exception JspException if a processing error occurs
     */
    public int doEndTag() throws JspException {
        
        JspWriter out = pageContext.getOut();
        
        try {
            
            // Render the beginning of this element
            out.println();
            out.print("<table ");
            if (columns > 2) {
                out.print(" columns=\"");
                out.print(columns);
                out.print("\"");
            }
            if (tableStyle != null) {
                out.print(" class=\"");
                out.print(tableStyle);
                out.print("\"");
                out.print(" border=\"1\" cellspacing=\"0\" ");
                out.print(" cellpadding=\"0\" width=\"100%\" ");
            }
            out.println(">");
            
            
            // Render each defined row
            int n = labels.size();
            for (int i = 0; i < n; i++) {
                String label = (String) labels.get(i);
                boolean header = ((Boolean) headers.get(i)).booleanValue();
                String data = (String) datas.get(i);
                String labelStyle = (String) labelStyles.get(i);
                String dataStyle = (String) dataStyles.get(i);
                String styleId = (String) styleIds.get(i);
                
                if (header)
                    out.println("<tr class=\"header-row\" >");
                else out.println("<tr>");
                
                out.println("  <td width=\"27%\"> ");
                
                out.print("    <div align=\"left\"");
                if (labelStyle != null)
                    out.print( " class=\"" + labelStyle +"\"");
                out.print(">");
                if (styleId != null) {
                    out.print("<label for=\"" + styleId + "\">");
                }
                out.print(label);
                if (styleId != null) {
                    out.print("</label>");
                }
                out.println("    </div>");
                out.println("  </td>");
                
                out.println("  <td width=\"73%\"> ");
                out.print("    <div align=\"left\"" );
                if (dataStyle != null)
                    out.print(" class=\"" + dataStyle + "\"");
                out.print(">");
                out.print(data);
                out.println("    </div>");
                out.print("  </td>");
                out.println("</tr>");
                
                /*
                if (!header) {
                    out.println("<tr height=\"1\">");
                    out.println("  <td class=\""+ lineStyle + "\" colspan=\"2\">");
                    out.println("    <img src=\"\" alt=\"\" width=\"1\" height=\"1\" border=\"0\">");
                    out.println("  </td>");
                    out.println("</tr>");
                }
                 */
            }
            
            // Render the end of this element
            out.println("</table>");
            out.println();
            
        } catch (IOException e) {
            throw new JspException(e);
        }

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                                   oname.toString() + "'");
        }


        // Render this value to our current output writer
        if (value != null) {
            JspWriter out = pageContext.getOut();
            try {
                out.print(value);
            } catch (IOException e) {
                throw new JspException("IOException: " + e);
            }
        }

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     * @exception JspException if a processing error occurs
     */
    public int doEndTag() throws JspException {


        TreeControl treeControl = getTreeControl();
        JspWriter out = pageContext.getOut();
        try {
            out.print
                ("<table border=\"0\" cellspacing=\"0\" cellpadding=\"0\"");
            if (style != null) {
                out.print(" class=\"");
                out.print(style);
                out.print("\"");
            }
            out.println(">");
            int level = 0;
            TreeControlNode node = treeControl.getRoot();
            render(out, node, level, treeControl.getWidth(), true);
            out.println("</table>");
        } catch (IOException e) {
            throw new JspException(e);
        }


        return (EVAL_PAGE);

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    {
        if( bodyContent != null )
        {
            try
            {
                JspWriter out = getPreviousOut();
                out.print(bodyContent.getString());
                bodyContent.clearBody();
            }
            catch( IOException e )
            {
                log.error("Unable to get inner tag text", e);

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        log.info("Request diff between version "+verold+" and "+vernew);


        if( ctx.getPage() != null )
        {
            JspWriter out = pageContext.getOut();


            String diff = engine.getDiff( ctx, 
                                          vernew.intValue(), 
                                          verold.intValue() );


            if( diff.length() == 0 )
            {
                return EVAL_BODY_INCLUDE;
            }


            out.write( diff );
        }


        return SKIP_BODY;
    }

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