Suggestions for Java email templating? [closed]

we have an application that needs to send out various different types of template email. The current code is very cumbersome and not very flexible. Does any one konw of a library to help with this type of work... We are looking for some kind of templating library for email.

StringTemplate is also a very nice template engine.

Perhaps Apache Velocity could work for you?

Jack Leow said he wrote a custom HttpServletResponse so that he could re-use JSPs for generating email templates, I just did the same and would like to share my code sample / prototype for those not sure where to begin:

Usually when serving a JSP page, you'd do something like this:

res.setContentType("text/html");
RequestDispatcher jsp = req.getRequestDispatcher("/WEB-INF/templates/" + template);
res.setStatus(200);
jsp.forward(req, res);

Now instead of doing that jsp.forward to an HttpServletResponse, do a jsp.forward to your custom Servlet Response:

EmailServletResponse res2 = new EmailServletResponse();
jsp.forward(req, res2);
System.out.println(res2.toString()); <<-- email gets printed here

Your EmailServlet response will simply be a class that implements HttpServletResponse, fill in the blanks and use an underlying StringWriter to accomplish the toString conversion:

public class EmailServletResponse implements HttpServletResponse {

private int status;
private StringWriter sw = new StringWriter();

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

@Override
public int getBufferSize() {
    return 1024;
}

@Override
public String getCharacterEncoding() {
    return "UTF-8";
}

@Override
public String getContentType() {
    return "text/html";
}

@Override
public Locale getLocale() {
    return Locale.getDefault();
}

@Override
public ServletOutputStream getOutputStream() throws IOException {
    return new ServletOutputStream() {
        @Override
        public void write(int b) throws IOException {
            sw.write(b);
        }
    };
}

@Override
public PrintWriter getWriter() throws IOException {
    PrintWriter pw = new PrintWriter(sw);
    return pw;
}

@Override
public boolean isCommitted() {
    return false;
}

@Override
public void reset() {       
}

@Override
public void resetBuffer() {
}

@Override
public void setBufferSize(int arg0) {
}

@Override
public void setCharacterEncoding(String arg0) {
}

@Override
public void setContentLength(int arg0) {
}

@Override
public void setContentType(String arg0) {
}

@Override
public void setLocale(Locale arg0) {
}

@Override
public void addCookie(Cookie arg0) {
}

@Override
public void addDateHeader(String arg0, long arg1) {
}

@Override
public void addHeader(String arg0, String arg1) {
}

@Override
public void addIntHeader(String arg0, int arg1) {
}

@Override
public boolean containsHeader(String arg0) {
    return false;
}

@Override
public String encodeRedirectURL(String arg0) {
    return "";
}

@Override
public String encodeRedirectUrl(String arg0) {
    return "";
}

@Override
public String encodeURL(String arg0) {
    return "";
}

@Override
public String encodeUrl(String arg0) {
    return "";
}

@Override
public void sendError(int arg0) throws IOException {

}

@Override
public void sendError(int arg0, String arg1) throws IOException {

}

@Override
public void sendRedirect(String arg0) throws IOException {

}

@Override
public void setDateHeader(String arg0, long arg1) {

}

@Override
public void setHeader(String arg0, String arg1) {


}

@Override
public void setIntHeader(String arg0, int arg1) {

}

@Override
public void setStatus(int status) {
    this.status = status;
}

@Override
public void setStatus(int status, String message) {
    setStatus(status);
}

public String toString(){
    return sw.getBuffer().toString();
}
}

Feel free to improve on the code where needed, this was a quick prototyping session :)

I ran into a similar problem about a year ago. In our case, our front end developers were all familiar with JSP, and I really did not want to throw another templating engine into the mix. I wanted something that relied on the servlet container's JSP processor to generate e-mail content for me.

It's fairly straightforward:

1. I had to have a JSP page in my application (you can put it in /WEB-INF if you don't want it externally accessible).
2. I wrote a custom HttpServletResponse and ServletOutputStream that captures content written by the servlet container and turns it into a String, and relied on RequestDispatcher.include(...) to make a "request" to the template JSP (I also wrote a custom HttpServletRequest to isolate the original request from mutation).
3. Because this is a bit of a hack, and not the way the servlet API was intended to be used, I encapsulated all this in a utility class, so that all the client code has to do is pass in the path to the JSP template, and get back the processed content.

I prefer Freemarker, here over Velocity; imo, Freemarker much simpler in this case.

If you are using Spring, then you may be interested in, Freemarker in Spring MVC.