de.xore.util.servlets.LayoutServlet Maven / Gradle / Ivy

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package de.xore.util.servlets;

import de.xore.util.SessionContext;
import de.xore.util.XoreException;
import de.xore.util.velocity.XoreVelocityFormatter;
import org.apache.velocity.Template;
import org.apache.velocity.context.Context;
import org.apache.velocity.servlet.VelocityServlet;
import org.jetbrains.annotations.NonNls;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Enumeration;

/*
 * Created by XoreSystems (Johannes Schneider).
 * User: Johannes
 * Date: 20.12.2003
 * Time: 16:55:59
 *
 */

/**
 * 
 * Date: 20.12.2003
 Time: 16:55:59

 *
 * @author Johannes Schneider - Xore
 *         Systems
 */
public abstract class LayoutServlet extends VelocityServlet {
  @NonNls
  public static final String CONTENT_TEMPLATE_NAME = "contentTemplateName";
  @NonNls
  private static final String EXCEPTION = "exception";
  @NonNls
  private static final String SESSION_CONTEXT = "context";
  @NonNls
  private static final String FORMATTER = "format";
  @NonNls
  protected static final String REDIRECT_URL = "REDIRECT_URL";

  protected boolean isStringEmpty( String string ) {
    return string == null || string.length() == 0;
  }

  @Override
  protected void error( @NotNull HttpServletRequest request, @NotNull HttpServletResponse response, @NotNull Exception cause ) throws ServletException, IOException {
    StringBuilder html = new StringBuilder();

    html.append( "" );
    html.append( "" );
    html.append( "
Fehler" );
    html.append( "" );
    html.append( cause );
    html.append( "
" );

    StringWriter sw = new StringWriter();
    cause.printStackTrace( new PrintWriter( sw ) );

    html.append( sw.toString() );
    html.append( "" );

    Enumeration attributeNames = request.getSession().getAttributeNames();
    while ( attributeNames.hasMoreElements() ) {
      String name = ( String ) attributeNames.nextElement();
      html.append( "" );
      html.append( name );
      html.append( ':' );
      html.append( request.getSession().getAttribute( name ) );
      html.append( "" );
    }

    html.append( "" );
    html.append( "" );
    response.getOutputStream().print( html.toString() );
  }

  @Override
  protected Template handleRequest( @NotNull HttpServletRequest request, @NotNull HttpServletResponse response, @NotNull Context ctx ) throws Exception {
    HttpSession session = request.getSession();
    SessionContext sessionContext = getSessionContext( session );
    refreshSessionContext( sessionContext );
    checkSecurity( sessionContext );

    ctx.put( SESSION_CONTEXT, sessionContext );
    ctx.remove( FORMATTER );
    ctx.put( FORMATTER, new XoreVelocityFormatter( ctx, request, response, sessionContext ) );
    try {
      //Diese Methode wird in der Sub-Klasse implementiert.
      handle( request, response, ctx, session, sessionContext );
    } catch ( XoreException e ) {
      postProcessingContext( request, response, ctx );
      ctx.put( EXCEPTION, e );
      ctx.put( CONTENT_TEMPLATE_NAME, "error.vm" );
      return getLayoutTemplate();
    }

    ctx.put( CONTENT_TEMPLATE_NAME, getContentTemplateName( request ) );
    postProcessingContext( request, response, ctx );

    if ( redirectUrl( request ) ) {
      response.sendRedirect( response.encodeRedirectURL( sessionContext.getRoot() + '/' + getRedirectUrl( request ) ) );
    }
    return getLayoutTemplate();
  }

  @Nullable @NonNls
  private String getRedirectUrl( @NotNull HttpServletRequest request ) {
    if ( getRedirectUrl() != null ) {
      return getRedirectUrl();
    }
    return ( String ) request.getAttribute( REDIRECT_URL );
  }

  private boolean redirectUrl( @NotNull HttpServletRequest request ) {
    return getRedirectUrl( request ) != null;
  }

  @Nullable @NonNls
  protected String getRedirectUrl() {
    return null;
  }

  /**
   * Nach Ablauf von handle() wird diese Methode durchgefuehrt. Dient z.B. zum Einhaengen von Standard-Werten in den
   * Context
   * 
   * Z.B. einhaengen des SessioNContext
   * @param ctx the context
   * @param request the request
   * @param response the response
   */
  protected abstract void postProcessingContext( @NotNull HttpServletRequest request, @NotNull HttpServletResponse response, @NotNull Context ctx );

  /**
   * Sicherheits-Ueberpruefungen (statisch bzw. deklarativ) koennen hier stattfinden. Wird direkt nach
   * refreshSessionContext und vor handle() aufgerufen.
   * @param sessionContext thhe session context
   * @throws XoreException the exception
   */
  public abstract void checkSecurity( @NotNull SessionContext sessionContext ) throws XoreException;

  /**
   * Vor dem Aufruf von handle() werden hier alle persistenten Objekte (Hibernate) aktualisiert.
   */
  public abstract void refreshSessionContext( @NotNull SessionContext sessionContext );

  /**
   * Liefert den SessionContext zu einer bestimmten Session bzw. legt ihn neu an
   */
  public abstract SessionContext getSessionContext( @NotNull HttpSession session );

  /**
   * Wird vom einzelnen Servlet ueberschrieben
   */
  protected abstract String getContentTemplateName( @NotNull HttpServletRequest request );

  /**
   * Liefert das "Haupt-Template", welches entsprechend das von getContentTemplateName zurückgegebene Template
   * inkludiert
   */
  public abstract Template getLayoutTemplate() throws Exception;

  protected abstract void handle( @NotNull HttpServletRequest request, @NotNull HttpServletResponse response, @NotNull Context ctx, @NotNull HttpSession session, @NotNull SessionContext sessionContext ) throws Exception;
}