datasourcefield_engine.java

java 写的一个新闻发布系统

//
//                                   ____.
//                       __/\ ______|    |__/\.     _______
//            __   .____|    |       \   |    +----+       \
//    _______|  /--|    |    |    -   \  _    |    :    -   \_________
//   \\______: :---|    :    :           |    :    |         \________>
//           |__\---\_____________:______:    :____|____:_____\
//                                      /_____|
//
//                 . . . i n   j a h i a   w e   t r u s t . . .
//

//
//  DataSourceField_Engine
//  EV      04.12.2000
//
//  getInstance()
//  authoriseRender()
//  renderLink()
//  needsJahiaData()
//  handleActions()
//

package org.jahia.engines.datasourcefield;

import java.io.*;                       // PrintWriter
import java.util.*;                     // Enumeration
import java.net.*;                      // URLEncoder

import org.jahia.utils.*;           // JahiaConsole
import org.jahia.data.*;            // JahiaData
import org.jahia.data.fields.*;     // JahiaField
import org.jahia.params.*;          // ParamBean
import org.jahia.engines.*;         // JahiaEngine interface, EngineParams
import org.jahia.registries.*;      // ServicesRegistry
import org.jahia.exceptions.JahiaException;


public class DataSourceField_Engine implements JahiaEngine {

    private static  DataSourceField_Engine  theObject   = null;
    private         String                  engineName  = "datasourcefield";



    /***
        * constructor
        * EV    04.12.2000
        *
        */
    private DataSourceField_Engine()
    {
        // JahiaConsole.println( "Engine", "***** Starting DataSourceField Engine *****" );
    } // end constructor



    /***
        * getInstance
        * EV    04.12.2000
        *
        */
    public static synchronized DataSourceField_Engine getInstance()
    {
        if (theObject == null) {
            theObject = new DataSourceField_Engine();
        }
        return theObject;
    } // end getInstance



    /***
        * authoriseRender
        * EV    04.12.2000
        *
        */
    public boolean authoriseRender( ParamBean jParams )
    {
        return (jParams.getOperationMode() == jParams.EDIT);
    } // end authoriseRender



    /***
        * renderLink
        * EV    04.12.2000
        * to be changed... normally, won't need a link
        *
        */
    public String renderLink( ParamBean jParams, Object theObj )
    throws JahiaException
    {
        JahiaField   theField    = (JahiaField) theObj;
        String params = "";
//        params += "&mode=displaywindow";
        params += "?mode=displaywindow";
        params += "&fid=" + theField.getID();
        return jParams.composeEngineUrl( engineName, params );
    } // end renderLink



    /***
        * needsJahiaData
        * EV    04.12.2000
        * it doesn't need JahiaData !!
        *
        */
    public boolean needsJahiaData( ParamBean jParams )
    {
        return false;
    } // end needsJahiaData



    /***
        * handleActions
        * EV    04.12.2000
        *
        */
    public void handleActions( ParamBean jParams, JahiaData jData )
    throws JahiaException
    {
        String  mode     = jParams.getRequest().getParameter( "mode" );
        String  ipAddr   = jParams.getRequest().getRemoteAddr();
        int     fid      = jParams.getFieldID();
        if (mode != null) {
            if (mode.equals("displaydata")) {
                JahiaConsole.println( "DataSourceField_Engine", ipAddr + " is accessing DataSourceField " + fid );
                handleFieldData( jParams );
            }
        }
    } // end handleAction



    /***
        * handleFieldData()
        * EV    04.12.2000
        *
        */
    public void handleFieldData( ParamBean jParams )
    throws JahiaException
    {
        String html         = "";
        String theValue     = "";

        int fieldID         = jParams.getFieldID();
        JahiaField theField = ServicesRegistry.getInstance().getJahiaFieldService().loadField( fieldID, jParams );
        if (theField != null) {
            theValue = theField.getValue();
        } else {
            theValue = "- error in retrieving field -";
        }
        sendFieldData( jParams, theValue );
    }
    // end handleFieldData



    /***
        * sendFieldData()
        * EV    04.12.2000
        *
        */
    public void sendFieldData( ParamBean jParams, String fieldValue )
    throws JahiaException
    {
        try {
            PrintWriter out = jParams.getResponse().getWriter();
            jParams.getResponse().setContentType( "text/html" );
            out.println( fieldValue );
        } catch (IOException ie) {
            String errorMsg = "Error while returning a datasource field : " + ie.getMessage() + " -> BAILING OUT";
            JahiaConsole.println( "DataSourceField_Engine", errorMsg );
            throw new JahiaException(   "Cannot retrieve remote data",
                                        errorMsg, JahiaException.DATA_ERROR, JahiaException.CRITICAL );
        }

    }
    // end sendFieldData


} // end DataSourceField_Engine