Getting JSP+JSTL view contents.

[Dust]

Hi,

I'm working on an application where we've decided to go with JSP+JSTL without using Velocity or Freemarker. Is there a way to get the full view contents as a String given the JSP template and parameters for the purpose of creating dynamic emails?

Basically I'm looking for the equivalent of the VelocityEngineUtils.mergeTemplateIntoString() without Velocity. Is this possible/practical?

Any help is appreciated.

[Dave Syer]

Basically I'm looking for the equivalent of the VelocityEngineUtils.mergeTemplateIntoString() without Velocity. Is this possible/practical?

Short answer: "no". JSP is not amenable to rendering outside a container.

[doclivingston]

The other day I made a custom JSP tag which renders other views in the middle of a JSP, which involves getting the view output as a string. Below is the code I used for doing this, which is based on assorted fragments of code I found on the 'net. I should work for any View, not just JSPs (mine are XSLT views).

/**
 * An output stream which stores it's content in an accessible string buffer.
 */
public class DummyOutputStream extends ServletOutputStream {
    private StringBuffer buffer = new StringBuffer();

    /** @{inheritDoc} */
    public String toString() {
        return buffer.toString();
    }
    /** @{inheritDoc} */
    public StringBuffer getBuffer() {
        return buffer;
    }

    /** @{inheritDoc} */
    public void write(final int b) throws IOException {
        buffer.append(b);
    }
    /** @{inheritDoc} */
    public void print(final boolean arg0) throws IOException {
        buffer.append(arg0);
    }
    /** @{inheritDoc} */
    public void print(final char arg0) throws IOException {
        buffer.append(arg0);
    }
    /** @{inheritDoc} */
    public void print(final double arg0) throws IOException {
        buffer.append(arg0);
    }
    /** @{inheritDoc} */
    public void print(final float arg0) throws IOException {
        buffer.append(arg0);
    }
    /** @{inheritDoc} */
    public void print(final int arg0) throws IOException {
        buffer.append(arg0);
    }
    /** @{inheritDoc} */
    public void print(final long arg0) throws IOException {
        buffer.append(arg0);
    }
    /** @{inheritDoc} */
    public void print(final String arg0) throws IOException {
        buffer.append(arg0);
    }
    /** @{inheritDoc} */
    public void println() throws IOException {
        buffer.append("\n");
    }
    /** @{inheritDoc} */
    public void println(final boolean arg0) throws IOException {
        buffer.append(arg0);
        buffer.append("\n");
    }
    /** @{inheritDoc} */
    public void println(final char arg0) throws IOException {
        buffer.append(arg0);
        buffer.append("\n");
    }
    /** @{inheritDoc} */
    public void println(final double arg0) throws IOException {
        buffer.append(arg0);
        buffer.append("\n");
    }
    /** @{inheritDoc} */
    public void println(final float arg0) throws IOException {
        buffer.append(arg0);
        buffer.append("\n");
    }
    /** @{inheritDoc} */
    public void println(final int arg0) throws IOException {
        buffer.append(arg0);
        buffer.append("\n");
    }
    /** @{inheritDoc} */
    public void println(final long arg0) throws IOException {
        buffer.append(arg0);
        buffer.append("\n");
    }
    /** @{inheritDoc} */
    public void println(final String arg0) throws IOException {
        buffer.append(arg0);
        buffer.append("\n");
    }
    /** @{inheritDoc} */
    public void write(final byte[] b) throws IOException {
        print(new String(b));
    }
    /** @{inheritDoc} */
    public void write(final byte[] b, final int off, final int len) throws IOException {
        write(ArrayUtils.subarray(b, off, off + len));
    }
}

/**
 * Wraps a HttpServletResponse to redirect the output to a StringBuffer.
 */
public class ContentAdapterResponseWrapper extends HttpServletResponseWrapper {
    private DummyOutputStream outstream;

    /**
     * Constructor.
     *
     * @param response the response to wrap
     */
    public ContentAdapterResponseWrapper(final HttpServletResponse response) {
        super(response);
        outstream = new DummyOutputStream();
    }

    /**
     * @return the string buffer containing the wrapped responses output
     */
    public StringBuffer getBuffer() {
        return outstream.getBuffer();
    }

    /** @{inheritDoc} */
    public ServletOutputStream getOutputStream() throws IOException {
        return outstream;
    }
    /** @{inheritDoc} */
    public PrintWriter getWriter() throws IOException {
        return new PrintWriter(outstream);
    }
    /** @{inheritDoc} */
    public String toString() {
        return outstream.toString();
    }
    /**
     * Override to always have the original content type.
     */
    public void setContentType(final String arg0) {
    }
}

You'd use the classes something like the following:

Map renderModel;
HttpServletRequest request;
HttpServletResponse response;
View someview;

ContentAdapterResponseWrapper proxyResponse = new ContentAdapterResponseWrapper(response);
proxyResponse.setContentType("application/xhtml+xml");

view.render(renderModel, request, proxyResponse);
String output = proxyResponse.getBuffer().toString();