Invoking a Java Method in JSP

Question

Setup Mac OSX 10.6.8, Apache Tomcat 6.0.16, Java1.6.0_29, Eclipse IDE Indigo.

I asked a similar question to this before at How to execute and include a Java API from a Web App project but the set up has since changed in that i now have the Java code in the WebAp

I am trying to invoke a Java Method from a JSP page and return the results. I have looked at a lot of posts but I’m afraid my lack of experience with either language is the main problem.

I have a JSP WebAp that searches an XML database and returns content to the user. I have been asked to integrate additional java code that searches predefined Websites and returns content.

I’ve played around with similar code to the below but I think I’m looking for something else

<%@ include file="/Applications/Tomcat/apache-tomcat-6.0.16/webapps/myWebApp/program.java" %>

Can anyone give me a better idea of what I’m looking for?

Also do you know if I have to edit anything else in the WebAp to connect the two files? The class files in the WebINF folder?

Any help is very much appreciated

Deepend

---

package sliceClient;

import java.util.List;


public class Run {

@Inject
private SliceSearcher sliceSearcher;

@Inject
private SliceCreator sliceCreator;

/**
 * @param args
 */
public static void main(String[] args) {
    Injector injector = Guice.createInjector(new GuiceInjector());
    Run r = injector.getInstance(Run.class);
    r.runSliceConsumer();
}

private void setSlicepediaProductionMode(boolean productionMode){
    sliceSearcher.setProductionMode(productionMode);
    sliceCreator.setProductionMode(productionMode);
}

public void runSliceConsumer() {
    System.out.println("Starting Slice Consumer");

    //Remove this line if the real slicepedia server is to be used
    setSlicepediaProductionMode(true);

    List<SliceHit> sliceHits = searchForSlices();
    if (sliceHits == null) {
        System.err.println("Timeout occurred while fetching slices");
        return;
    }
    if (!sliceHits.isEmpty()) {
        System.out.println("Found some slices Yuhuuuu ! :-) ");
        String sliceContent = createSlices(sliceHits);
        System.out.println("Slice content:");
        System.out.println(sliceContent);
    } else {
        System.out.println("No Slices were found for this query");
    }
    System.out.println("Slice Consumer stopped activity");
}

private String createSlices(List<SliceHit> sliceHits) {
    sliceCreator.setSliceHits(sliceHits);
    if (sliceCreator.run()) {
        SlicePackage slicePackage = sliceCreator.getNextSlicePackage();
        return slicePackage.getSliceContent();
    } else {
        return sliceCreator.getErrorMessage();
    }
}

private List<SliceHit> searchForSlices() {
    SlicepediaQuery sliceQuery = new SlicepediaQuery();


    sliceQuery.paramANNOTATION_READING_DIFFICULTY(new Double(30), "<");
    //Works
//      String dbConcept = "http://dbpedia.org/resource/human_rights";
//      sliceQuery.paramANNOTATION_CONCEPT_FEATURE_HAS_DBPEDIA(dbConcept,0.5, ">");
//      sliceQuery.paramHAS_NBR_OF_PARAGRAPHS(1,">");
//      sliceQuery.paramIsAnOpenSlice(true);
//      sliceQuery.paramHasNumberOfToken(80, ">");

    sliceSearcher.setSliceQuery(sliceQuery);
    if (sliceSearcher.run()) {
        return sliceSearcher.getSliceHits();

    } else {
        return null;

    }
}

}

Answer 1

First, the ugly way (maybe because so similar to php?):

<%= com.example.MyUtility.getSomething() %>

It is called a scriptlet and is considred a bad practice. In fact this is so wrong that I am ashamed of even writing this. What you should do instead is to have a front controller (a simple servlet will do the trick), place results in the request attributes and forward to a JSP, which in turns uses jstl or jsp el for output. Much more work, but better by an order of magnitude:

In Servlet:

request.setAttribute("someData", MyUtility.getSomething())
RequestDispatcher dispatcher = request.getRequestDispatcher("page.jsp");
dispatcher.forward(request, response);  

In page.jsp:

${someData}

There are various frameworks that can reduce the amount of boilerplate (spring-mvc is a simple example).