persistenceexample2/PersistenceExample.java


package persistenceexample2;
import java.io.IOException;
import java.util.Vector;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import persistenceexample2.bean.TableViewBean;
import persistenceexample2.datafactory.ReadWriteEntities;

import com.sap.ip.me.api.logging.AbstractLogging;
import com.sap.ip.me.api.logging.AppLog;
import com.sap.ip.me.api.logging.Severities;
import com.sap.ip.me.api.runtime.jsp.AbstractMEHttpServlet;

// Uses the Peristence API to store and read data

public class PersistenceExample extends AbstractMEHttpServlet implements Constants {

    public static int idCounter;
    private TableViewBean tableViewBean;

    private String headLine;
    boolean listall;
    private int filter_index;
    private int sort_index;
    private boolean sort_ascending;
    private String buttontext;
    private String buttontextQuery;
    private String filter_string;
    /**
     * Must be overwritten - return the name of the application
     */
    public String getApplicationName() {
        return MI_APPLICATION_NAME;
    }

    /**
     * doIntialize - called when the servlet is activated the first time
     */
    public void doInitialize() throws ServletException {
        /* No resource bundle used    setResourceBundle("/NoResourceBundleUsed"); */

        idCounter = 0;

        // Setup and initialize the Persistence Runtime
        ReadWriteEntities.setupPersistenceRuntime();

        // We create initial entries with the Persistence API, so that we have not to display an emtpy table
        ReadWriteEntities.writeExampleEntries();

        // Set list parameter to list only main entries
        setListPartial();
        setFilterOff();

        // Set sorting variables.
        sort_index = 0;
        sort_ascending = true;

        //    Prepare a log output - Level DEBUG - Information about classloader
        ClassLoader cl = getClass().getClassLoader();
        AbstractLogging aLogger = AppLog.getInstance(MI_APPLICATION_NAME);
        aLogger.log(Severities.DEBUG, "MIClientInfo: Create MIClientInfoServlet.doInitialize with Classloader {0}", (cl == null ? "(null)" : cl.toString()));
    }

    /**
     * doHandleEvent - called any subsequent time when an event on the web client occurs.
     */

    public String doHandleEvent(String eventName, HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // Set the name of the JSP that has to be called when this method is finished.
        // INITIAL_JSP ist defined in the interface Constants.java and refers to welcome.jsp. This JSP displays a welcome message
        // and asks for your name. Welcome.jsp has a submit button which generates the event EVENT_NAME. When this event occurs,
        // the tableView.jsp is called and displays system information.
        // The welcome.jsp is called by default - if the servlet is called the first time or an unknown event occurs.

        // Set default JSP.
        String nextJSP = INITIAL_JSP;
        // Set default text for headline
        headLine = WELCOME_MESSAGE;

        // Get bean, if there is one, in the session context, otherwise create a new instance.
        getBeansFromContext(request);

        //
        // Events in menu.jsp

        if (eventName.equals(EVENT_LIST)) {
            // Toggle on listall (boolean) - if acutally true than set to false and vice versa
            if (listall == true) {
                setListPartial();
            } else {
                setListAll();
            }
        }

        if (eventName.equals(EVENT_ADDENTRY)) {
            // Event occurs when the ADD button in menu.jsp has been pressed.
            // We display add.jsp as next JSP.
            nextJSP = ADD_JSP;
        }

        if (eventName.equals(EVENT_QUERY)) {
            // Event occurs when the FILTER button in menu.jsp has been pressed.
            // We display query.jsp.
            nextJSP = QUERY_JSP;
        }

        if (eventName.equals(EVENT_DELENTRY)) {
            // Event occurs when the DELETE button in menu.jsp has been pressed.
            nextJSP = deleteEntry(request);
        }

        if (eventName.equals(EVENT_SAVE)) {
            // Event occurs when the SAVE button in menu.jsp has been pressed. 
            ReadWriteEntities.commit();
        }
        //
        // Events from add.jsp or delete.jsp (Cancel event - is handled the same for both JSP
        //
        if (eventName.equals(EVENT_ADDENTRYCANCEL)) {
            // Event occurs when the cancel button has been pressed on the ADD ENTRY JSP. No action. Show initial screen
            nextJSP = INITIAL_JSP;
        }

        //
        // Events in add.jsp
        //
        if (eventName.equals(EVENT_ADDENTRYSUBMIT)) {
            // Event occurs when the submit button has been pressed on the ADD ENTRY JSP
            nextJSP = addEntry(request);
        }

        //
        // Event in delete.jsp - is the OK button to acknowledge the information text
        //
        if (eventName.equals(EVENT_DELETEENTRYSUBMIT)) {
            nextJSP = INITIAL_JSP;
        }

        //
        // Event in query.jsp
        //
        if (eventName.equals(EVENT_QUERYCANCEL)) {
            // Event occurs when the cancel button has been pressed on the Cancel button. No action. Show initial screen
            nextJSP = INITIAL_JSP;
        }

        if (eventName.equals(EVENT_QUERYSUBMIT)) {
            // Event occurs when the OK button has been pressed. The Filter string is set for the Query.
            nextJSP = setFilter(request);
        }

        // Load bean with values from persistence layer
        loadBean(listall);

        // Put bean in the session context.
        putBeansIntoContext(request);

        // Exit with name of JSP.
        return nextJSP;
    }

    /**
     * Method deleteEntry - deletes an selected entry
     * @return String - next JSP to call.
     */
    private String deleteEntry(HttpServletRequest request) {
        String nextJSP = null;
        // We loop through all entries and check
        // which row has been selected. If we find a selected row we delete the entry.
        // We use the request.getParameter(valueOfCheckbox) method to find out which checkbox is clicked. The valueOfCheckbox
        // is stored in the first column of the databean.
        // If no row is selected we display a hint to select a row first.
        boolean aRowWasChecked = false;
        for (int i = 1; i < tableViewBean.getTableRows(); i++) {
            String check = (String) request.getParameter(tableViewBean.getTableContent(i, 0));
            if (check != null) {
                // Check Row has been found
                aRowWasChecked = true;
                String car = tableViewBean.getTableContent(i, 0);

                // Delete car. License is deleted also, because we use TreeOptionType.COMPLETE in the deleteEntity method
                if (car.length() > 0) {
                    ReadWriteEntities.deleteEntity(car);
                }
            }
        }

        nextJSP = INITIAL_JSP;
        if (aRowWasChecked == false) {
            // no row was checked - display an information message
            nextJSP = DELETE_JSP;
        }

        return nextJSP;
    }

    /**
     * Method addEntry. - Adds an Entry according to user input
     * @return String - next JSP to call
     */
    private String addEntry(HttpServletRequest request) {

        // We take the content of the inputfield in the JSP named CAR and LICENCE and store in via the Peristence API
        // As next JSP we set the INITIAL_JSP again.
        String make = (String) request.getParameter("MAKE");
        String model = (String) request.getParameter("MODEL");
        String engine = (String) request.getParameter("ENGINE");
        String cylinders = (String) request.getParameter("CYLINDERS");
        String valves = (String) request.getParameter("VALVES");
        String lic = (String) request.getParameter("LICENSE");

        ReadWriteEntities.addEntity(make, model, engine, cylinders, valves, lic);

        return INITIAL_JSP;
    }

    /**
     * Method setFilter - according to user input a filter string will be set up.
     * @param request
     * @return String - next JSP to call
     */
    private String setFilter(HttpServletRequest request) {

        filter_string = (String) request.getParameter("MAKE");
        if (filter_string.length() == 0) {
            setFilterOff();
        } else {
            // The filter_index has to match the "AttributeDescriptor" in ExamplePackagePersistenceMaster. I_MAKE is the
            // index for our output array, which has the entityKey at index 0. The "AttributeDescriptor" has no entityKey
            // and starts with "make" right away - so we subtract 1 from the I_MAKE index.
            setFilterOn(I_MAKE - 1, filter_string);
        }
        return INITIAL_JSP;
    }

    private void getBeansFromContext(HttpServletRequest request) {
        // Get table defintion bean from session context. There is a bean, when this servlet has already been called once.
        tableViewBean = (TableViewBean) request.getSession().getAttribute(CONTEXT_BEAN);
        // No bean in session context - create a new instance.
        if (tableViewBean == null)
            tableViewBean = new TableViewBean();
    }

    public void loadBean(boolean all) {
        //     Set headline
        tableViewBean.setString(headLine);
        //     Set button text for list button
        tableViewBean.setButton(buttontext);
        //     Set button text for query button
        tableViewBean.setButtonQuery(buttontextQuery);

        //     Read data from persistence layer according to filter settings.
        Vector ent = new Vector();

        // create header
        /* The "Make" and "Model" (index 1 and 2) headline can be clicked by the user to select which column is sorted by. That the event
            * of the link is passed on to this servlet and also tells us which link has been clicked, we use the ?event=
            * paramenter on the "href" tag. A image indiactes which column is active for sorting. The getMime... methods
            * return either a "nosort.gif" (this column is not used for sorting) or "ascending.gif" when the column is
            * used for sorting
            */
        Vector dataVec = new Vector();
        dataVec.addElement(" ");
        dataVec.addElement("Make");
        dataVec.addElement("Model");
        dataVec.addElement("License");
        dataVec.addElement("Engine");
        dataVec.addElement("C");
        dataVec.addElement("V");
        ent.addElement(dataVec);

        ent = ReadWriteEntities.readEntity(ent, filter_index, sort_index, sort_ascending, filter_string, all);

        tableViewBean.setTableContent(ent);
        tableViewBean.setTableRows(ent.size());
        tableViewBean.setTableColumns(7);
    }

    /**
     * Method getMimeModelFileName. - gets the apporiate filename to indicate sorting direction for model
     * @return String
     */
    private String getMimeMakeFileName() {
        String mime = "mimes/nosort.gif";
        if (sort_index == I_MAKE - 1) {
            mime = "mimes/ascending.gif";
            if (sort_ascending == false)
                mime = "mimes/descending.gif";
        }
        return mime;
    }

    private String getMimeModelFileName() {
        String mime = "mimes/nosort.gif";
        if (sort_index == I_MODEL - 1) {
            mime = "mimes/ascending.gif";
            if (sort_ascending == false)
                mime = "mimes/descending.gif";
        }
        return mime;
    }

    private void putBeansIntoContext(HttpServletRequest request) {
        // Put table definition bean in session context
        if (tableViewBean == null) {
            request.getSession().removeAttribute(CONTEXT_BEAN);
        } else {
            request.getSession().setAttribute(CONTEXT_BEAN, tableViewBean);
        }
    }

    public void setListPartial() {
        listall = false;
        buttontext = " List all ";
    }

    public void setListAll() {
        listall = true;
        buttontext = "Short List";
    }
    /**
     * Method setFilterOff - All Data without Filter are displayed.
     */
    private void setFilterOff() {
        filter_index = I_ALL;
        buttontextQuery = BUTTON_QUERY_TEXT;

    }

    private void setFilterOn(int Index, String filter_string) {
        buttontextQuery = "Filter: " + filter_string;
        filter_index = I_MAKE - 1;
    }

}