minify html and js in jersey Interceptor

Question

used jersey mvc and jsp, all requests to html or js files did through @Template or Viewable. example;

  @GET
  @Path(JS_URL + "{type}")
  @Template(name = "grid")
  @Produces("application/javascript")
  public Response buildJSGrid(@DefaultValue("") @PathParam("type") String type) {
     Grid grid = new Grid(type);
....
     return Response.ok(grid).build();
  }

where grid is grid.jsp file with pure javascript inside

<%@ page contentType="application/javascript;charset=UTF-8" language="java" %>

.....

also possible other variant with html and js, example;

@GET
  @Path(FORM_URL + "{type}")
  @Template(name = "form")
  @Produces(MediaType.TEXT_HTML)
  public Response buildAccountForm(@DefaultValue("") @PathParam("type") String type) {
     Form form = new Form(type);
....
     return Response.ok(form).build();
  }

where form is form.jsp with html and js inside <script>..</script>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

...

i need to minify result js and html/js before send to client, i try to use https://code.google.com/archive/p/htmlcompressor/ lib, but there need to pass String to htmlCompressor.compress(input);

tried use WriterInterceptor

public class MinifyJsInterceptor implements WriterInterceptor {
  @Override
  public void aroundWriteTo(WriterInterceptorContext context) throws IOException, WebApplicationException {
final OutputStream outputStream = context.getOutputStream();
// here need to convert outputStream to InputStream and after to String ?
// result string to htmlCompressor.compress(resultString);
// after that convert result minify string back to resultOutputStream and set to context ?
context.setOutputStream(new GZIPOutputStream(resultOutputStream));

is it correct way ? and i can`t converts that outputstream to string thanks

--update

answer to questions; html + js mean that in some jsp are html markup and js code

    <div id="form" style="width: 500px; display: none">
      <div class="w2ui-page page-0">
        <div class="w2ui-field">
    </div>....

    <script type="text/javascript">
      var uiElement = (function () {
        var config = {
            onOpen: function (event) {
      event.onComplete = function () {
        $('#formContainer').w2render('form');
      }
     ...
    }());
    </script>

on client that file requested by

         $('#tempContainer').load('that file name - also dynamic', function (data, status, xhr) {
           uiElement.init();
           w2ui[layout].content(layout_main, w2ui[uiElement.name]);
         });

And do you really return js-files in you resource methods?

        some js and html + js files are dynamic build, example;
        grid.jsp contains inside

<%@ page contentType="application/javascript;charset=UTF-8" language="java" %>

          var uiElement = (function () {
            var config = {
              grid: {
                name: ${it.name},
                listUrl:'${it.entityListUrl}',
                formUrl:'${it.entityFormUrl}',
                columns: ${it.columns},
                records: ${it.records},           
}}

there are ${it..} values from el expression and setting in resource method

@GET
      @Path(JS_URL + "{type}")
      @Template(name = "grid")
      @Produces("application/javascript")
      public Response buildJSGrid(@DefaultValue("") @PathParam("type") String type) {
         Grid grid = new Grid(type);
    ....
         return Response.ok(grid).build();
      }}

and from client that js 'file' called by

         $.getScript('dynamic js file name' - it is dynamic too).done(function (script, status, xhr) {
           //console.log(xhr.responseText);
           uiElement.init();
           w2ui[layout].content(layout_main, w2ui[uiElement.name]);
         });



       also some html blocks build dynamic


{ 
     <c:if test="${it.recid != 0}">
          <div class="w2ui-field">
            <label>active:</label>
            <div>
              <input name="active" type="checkbox"/>
            </div>
          </div>
            </c:if>
}

-- update description, grid builder;

one resource and one template for build any grid,

  @GET
  @Path(GRID + "{type}")
  @Template(name = W2UI_VIEW_PREFIX + "grid/grid")
  @Produces(MEDIA_TYPE_APPLICATION_JAVASCRIPT)
  public Response buildGrid(@DefaultValue("") @PathParam("type") String type) {
    for (W2UI ui : W2UI.values()) {
      if (type.equals(ui.getName())) {
        W2UIElement grid = ui.getUI();
        return Response.ok(grid).build();
      }
    }
    return Response.noContent().build();
  }

also possible different templates(jsp files) through Viewable(template, model)

somewhere in menu builder for menu.jsp template

List<MenuItem> items..
MenuItem item1 = new MenuItem(W2UI.TASK_GRID, W2UIService.GRID);
items.add(item1);

where

W2UIService.GRID is string url for client js request and for server method resource @Path() anno.

and

public enum W2UI {
  TASK_GRID("task_grid", "tasks", Type.SCRIPT){
    @Override
    public W2UIElement getUI() {
      return new TaskGrid(getName());
    }
  },
.....
}

TaskGrid is filled model for grid.jsp template with js code, so easy to add any type of grid with different sets of data and buttons.

type of component(Type.SCRIPT) processing on the client by $.getScript(), Type.HTML by $('#tempContainer').load()

---update factory and providers;

@Provider
@Priority(200)
@HtmlMinify
public class HtmlMinifyInterceptor implements WriterInterceptor {
  @Inject private HtmlCompressor compressor;

...

public class HtmlMinifierFactory implements Factory<HtmlCompressor> {
  private HtmlCompressor compressor;

  @Override
  public HtmlCompressor provide() {
    if (null == compressor) compressor = new HtmlCompressor();
    ClosureJavaScriptCompressor jsCompressor = new ClosureJavaScriptCompressor();
    jsCompressor.setCompilationLevel(CompilationLevel.SIMPLE_OPTIMIZATIONS);

..

@ApplicationPath("/")
public class MainRsConfig extends ResourceConfig {
  public MainRsConfig() {
..
    register(new AbstractBinder() {
      @Override
      protected void configure() {
        bindFactory(HtmlMinifierFactory.class).to(HtmlCompressor.class).in(Singleton.class);
      }
    });
..

Answer 1

You can use a custom implementation of a ByteArrayOutputStream as a wrapper to the OutputStream of the WriterInterceptorContext:

import com.googlecode.htmlcompressor.compressor.Compressor;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;

public class HtmlMinifyOutputStream extends ByteArrayOutputStream {

    private OutputStream origOut;
    private Compressor compressor;

    public HtmlMinifyOutputStream(OutputStream origOut, Compressor compressor) {
        this.origOut = origOut;
        this.compressor = compressor;
    }

    public void close() throws IOException {
        super.close();
        String compressedBody = compressor.compress(new String(this.buf));
        this.origOut.write(compressedBody.getBytes());
        this.origOut.close();
    }
}

The HtmlMinifyOutputStream can be used in the WriterInterceptor implementation. The HtmlCompressor instance is injected:

import com.googlecode.htmlcompressor.compressor.Compressor;
import javax.inject.Inject;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.ext.Provider;
import javax.ws.rs.ext.WriterInterceptor;
import javax.ws.rs.ext.WriterInterceptorContext;
import java.io.*;

@Provider
@HtmlMinify
public class MinifyHtmlInterceptor implements WriterInterceptor {

    @Inject
    private Compressor compressor;

    @Override
    public void aroundWriteTo(WriterInterceptorContext context) throws IOException, WebApplicationException {
        final OutputStream outputStream = context.getOutputStream();
        context.setOutputStream(new HtmlMinifyOutputStream(outputStream, compressor));
        context.proceed();
    }
}

@HtmlMinify is a NameBinding annotation, used to activate the MinifyHtmlInterceptor on specific resource methods. (see https://jersey.java.net/documentation/latest/filters-and-interceptors.html#d0e9988):

import javax.ws.rs.NameBinding;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@NameBinding
@Retention(value = RetentionPolicy.RUNTIME)
public @interface HtmlMinify {}

The HtmlCompressor can be created only once per application and used concurrently, because:

HtmlCompressor and XmlCompressor classes are considered thread safe* and can be used in multi-thread environment
(https://code.google.com/archive/p/htmlcompressor/)

Here is a HK2 factory (see: Implementing Custom Injection Provider) which creates the compressor instance and enables inline css and javascript compression:

import com.googlecode.htmlcompressor.compressor.Compressor;
import com.googlecode.htmlcompressor.compressor.HtmlCompressor;
import org.glassfish.hk2.api.Factory;

public class HtmlCompressorFactory implements Factory<Compressor> {

    private HtmlCompressor compressor;

    @Override
    public Compressor provide() {
        if(compressor == null) {
            compressor = new HtmlCompressor();
        }
        compressor.setCompressJavaScript(true);
        compressor.setCompressCss(true);
        return compressor;
    }

    @Override
    public void dispose(Compressor compressor) {}
}

The factory is registered with an AbstractBinder:

final ResourceConfig rc = new ResourceConfig().packages("com.example");
rc.register(new AbstractBinder() {
    @Override
    protected void configure() {
        bindFactory(HtmlCompressorFactory.class).to(Compressor.class).in(Singleton.class);
    }
});

If inline javascript or inline css compression is enabled:

HTML compressor with default settings doesn't require any dependencies.
Inline CSS compression requires YUI compressor library.
Inline JavaScript compression requires either YUI compressor library (by default) or Google Closure Compiler library.
(https://code.google.com/archive/p/htmlcompressor/)

I use maven, so I added this dependency to my pom.xml:

<dependency>
    <groupId>com.yahoo.platform.yui</groupId>
    <artifactId>yuicompressor</artifactId>
    <version>2.4.8</version>
</dependency>

If you want to use the Google Closure Compiler use this dependency:

<dependency>
    <groupId>com.google.javascript</groupId>
    <artifactId>closure-compiler</artifactId>
    <version>r2388</version>
</dependency>

and activate it:

compressor.setJavaScriptCompressor(new ClosureJavaScriptCompressor());
compressor.setCompressJavaScript(true);
compressor.setCssCompressor(new YuiCssCompressor());
compressor.setCompressCss(true);
return compressor;

If you want to compress pure JavaScript or CSS files, you cannot use the htmlcompressor. This library supports only HTML files with inline CSS/JS. But you could implement a MinifyJsInterceptor or MinifyCssInterceptor analog to the MinifyHtmlInterceptor, which uses the YUI-Compressor and/or Google Closure libraries directly.

For gzip compression you should implement another interceptor. So it is possible to configure the minification and compression separately. If you activate multiple interceptors, use javax.annotation.Priority to controll the order of execution. (see: https://jersey.java.net/documentation/latest/filters-and-interceptors.html#d0e9927)