package info.evansweb.spring.examples.flash;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

/**
 * Copyright 2007 Jon Evans, jon@springyweb.com
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 * 
 * This class implements a Flash object for Spring MVC, inspired by the flash
 * object available to views in Rails (rubyonrails.org)
 *
 * @author Jon Evans, jon@springyweb.com
 *
 */
public class Flash {
  private static final String NOTICE = "notice";
  private static final String ERROR = "error";
  
  private Map<String, FlashEntry> data = new HashMap<String, FlashEntry>();
  
  public void clear() {
    this.data.clear();
  }
  
  public void decr() {
    Iterator<FlashEntry> it = data.values().iterator();
    while (it.hasNext()) {
      FlashEntry entry = it.next();
      int ttl = entry.decr();
      if (ttl <= 0) {
        it.remove();
      }
    }
  }

  /** Set an arbitrary key / value / ttl message */
  public void set(String key, String value, int ttl) {
    data.put(key, new FlashEntry(value, ttl));
  }
  /** Set an key / value message with default ttl message */
  public void set(String key, String value) {
    data.put(key, new FlashEntry(value));
  }
  /** Set a NOTICE message */
  public void set(String value) {
    data.put(NOTICE, new FlashEntry(value));
  }

  /** Set a message for the current request only */
  public void setCurrent(String key, String value) {
    data.put(key, new FlashEntry(value, 1));
  }
  /** Set a NOTICE message for the current request only */
  public void setCurrent(String value) {
    data.put(NOTICE, new FlashEntry(value, 1));
  }

  /** Set a NOTICE message with a ttl */
  public void setNotice(String value, int ttl) {
    data.put(NOTICE, new FlashEntry(value, ttl));
  }
  /** Set a NOTICE message with default ttl */
  public void setNotice(String value) {
    data.put(NOTICE, new FlashEntry(value));
  }
  /** Set an ERROR message with a ttl */
  public void setError(String value, int ttl) {
    data.put(ERROR, new FlashEntry(value, ttl));
  }
  /** Set an ERROR message with default ttl */
  public void setError(String value) {
    data.put(ERROR, new FlashEntry(value));
  }

  public String getValue(String key) {
    if (data.containsKey(key)) {
      return data.get(key).getValue();
    } else {
      return null;
    }
  }
  public String getNotice() {
    return getValue(NOTICE);
  }
  public String getError() {
    return getValue(ERROR);
  }

  public class FlashEntry {
    private String value;
    
    // Default ttl is 2, this request, and the following request
    private int ttl = 2;
    
    public FlashEntry(String value) {
      this.value = value;
    }
    
    public FlashEntry(String value, int ttl) {
      this(value);
      this.ttl = ttl;
    }
    
    public int getTTL() {
      return ttl;
    }
    public void setTTL(int ttl) {
      this.ttl = ttl;
    }

    public int decr() {
      return --ttl;
    }
    
    public String getValue() {
      return value;
    }
  }
  
  public String toString() {
    return "Flash [" + data.size() + " message(s)]";
  }
}

package info.evansweb.spring.examples.flash;

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

import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

/**
 * Copyright 2007 Jon Evans, jon@springyweb.com
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 * 
 * @author Jon Evans, jon@springyweb.com
 *
 */
public class FlashDecrementer extends HandlerInterceptorAdapter {

  private Flash flash;

  public void setFlash(Flash flash) {
    this.flash = flash;
  }

  public void decr() {
    if (flash!=null) {
      flash.decr();
    }
  }

  public void afterCompletion(HttpServletRequest request,
      HttpServletResponse response, Object handler, Exception exception)
      throws Exception {
    decr();
  }
}

  @Autowired
  private Flash flash;

  @RequestMapping("/login.do")
  public ModelAndView login() {
    // Do your login stuff here...
    flash.setNotice("Welcome back!");

    ModelAndView mav = new ModelAndView("redirect:/home.do");
    return mav;
  }