java Spring MVC 自定义作用域 bean

Spring MVC custom scope bean

提问by danny.lesnik

I would like to create my own custom scope bean which will use HTTP session (kind of Flash scope).

我想创建我自己的自定义范围 bean，它将使用 HTTP 会话（一种 Flash 范围）。

According to Spring Manual I need to implement org.springframework.beans.factory.config.Scope interface

根据 Spring Manual 我需要实现 org.springframework.beans.factory.config.Scope 接口

public class CustomScope implements Scope {

    @Override
    public Object get(String arg0, ObjectFactory<?> arg1) {
        // TODO Auto-generated method stub
        return null;
    }
    @Override
    public String getConversationId() {
        // TODO Auto-generated method stub
        return null;
    }
    @Override
    public void registerDestructionCallback(String arg0, Runnable arg1) {
        // TODO Auto-generated method stub
    }
    @Override
    public Object remove(String arg0) {
        // TODO Auto-generated method stub
        return null;
    }
    @Override
    public Object resolveContextualObject(String arg0) {
        // TODO Auto-generated method stub
        return null;
    }
}

My question is how can I obtain HTTP session inside of this bean? I understand that if I was creating bean in ServletContext scope I would implement ServletContextAware interface.

我的问题是如何在这个 bean 中获取 HTTP 会话？我知道如果我在 ServletContext 范围内创建 bean，我将实现 ServletContextAware 接口。

Please help :)

请帮忙 ：）

回答by danny.lesnik

I hope it will be useful for someone in the future, so I would like to share it.

我希望它对未来的某人有用，所以我想分享它。

I made some reserch on it and have found that unfortunately, it is impossible to get HTTP Session for Spring MVC.

我对它进行了一些研究，发现不幸的是，无法获得 Spring MVC 的 HTTP Session。

My purpose was Flash Scope implementation for my Spring MVC Controller using PRG pattern.

我的目的是使用 PRG 模式为我的 Spring MVC 控制器实现 Flash Scope。

Making more research in Spring Forum I've found the way to do it using HandlerInterceptor.

在 Spring Forum 中进行了更多研究，我找到了使用 HandlerInterceptor 完成它的方法。

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

import java.util.*;
import java.util.Map.Entry;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class FlashScopeInterceptor implements HandlerInterceptor {

    public static final String DEFAULT_ATTRIBUTE_NAME = "flashScope";
    public static final String DEFAULT_SESSION_ATTRIBUTE_NAME = FlashScopeInterceptor.class.getName();
    public static final int DEFAULT_RETENTION_COUNT = 2;

    private String sessionAttributeName = DEFAULT_SESSION_ATTRIBUTE_NAME;
    private String attributeName = DEFAULT_ATTRIBUTE_NAME;
    private int retentionCount = DEFAULT_RETENTION_COUNT;

    /**
     * Unbinds current flashScope from session. Rolls request's flashScope to
     * the next scope. Binds request's flashScope, if not empty, to the session.
     * 
     */

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        if (request.getSession( false ) != null)
        {
            request.getSession().removeAttribute( this.sessionAttributeName );
        }
        Object requestAttribute = request.getAttribute( this.attributeName );
        if (requestAttribute instanceof MultiScopeModelMap)
        {
            MultiScopeModelMap attributes = (MultiScopeModelMap) requestAttribute;
            if (!attributes.isEmpty())
            {
                attributes.next();
                if (!attributes.isEmpty())
                {
                    request.getSession( true ).setAttribute( this.sessionAttributeName, attributes );
                }
            }
        }
    }

    /**
     * merge modelAndView.model['flashScope'] to current flashScope
     */
    @Override
    public void postHandle( HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        if (modelAndView != null)
        {
            Map<String, Object> modelFlashScopeMap = null;
            for (Iterator<Entry<String, Object>> iterator = ((Map<String, Object>) modelAndView.getModel()).entrySet()
                    .iterator(); iterator.hasNext();)
            {
                Entry<String, Object> entry = iterator.next();
                if (this.attributeName.equals( entry.getKey() ) && entry.getValue() instanceof Map)
                {
                    if (modelFlashScopeMap == null)
                    {
                        modelFlashScopeMap = (Map) entry.getValue();
                    }
                    else
                    {
                        modelFlashScopeMap.putAll( (Map) entry.getValue() );
                    }
                    iterator.remove();
                }
                else if (entry.getKey().startsWith( this.attributeName + "." ))
                {
                    String key = entry.getKey().substring( this.attributeName.length() + 1 );
                    if (modelFlashScopeMap == null)
                    {
                        modelFlashScopeMap = new HashMap<String, Object>();
                    }
                    modelFlashScopeMap.put( key, entry.getValue() );
                    iterator.remove();
                }
            }
            if (modelFlashScopeMap != null)
            {
                MultiScopeModelMap flashScopeMap;
                if (request.getAttribute( this.attributeName ) instanceof MultiScopeModelMap)
                {
                    flashScopeMap = (MultiScopeModelMap) request.getAttribute( this.attributeName );
                }
                else
                {
                    flashScopeMap = new MultiScopeModelMap( this.retentionCount );
                }
                flashScopeMap.putAll( modelFlashScopeMap );
                request.setAttribute( this.attributeName, flashScopeMap );
            }
        }
    }

    /**
     * binds session flashScope to current session, if not empty. Otherwise cleans up empty
     * flashScope
     */
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        HttpSession session = request.getSession( false );
        if (session != null)
        {
            Object sessionAttribute = session.getAttribute( this.sessionAttributeName );
            if (sessionAttribute instanceof MultiScopeModelMap)
            {
                MultiScopeModelMap flashScope = (MultiScopeModelMap) sessionAttribute;
                if (flashScope.isEmpty())
                {
                    session.removeAttribute( this.sessionAttributeName );
                }
                else
                {
                    request.setAttribute( this.attributeName, flashScope );
                }
            }
        }
        return true;
    }
}

Now MultiScopeModelMap.java

现在 MultiScopeModelMap.java

import java.io.Serializable;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Set;

import org.apache.commons.collections.map.CompositeMap;
import org.apache.commons.collections.map.CompositeMap.MapMutator;

public class MultiScopeModelMap extends CompositeMap implements Serializable, MapMutator
{
    public MultiScopeModelMap(int num)
    {
        super();
        setMutator( this );
        for(int i = 0; i < num; ++i)
        {
            addComposited( new HashMap() );
        }
    }

    /** Shadows composite map. */
    private final LinkedList<Map> maps = new LinkedList<Map>();

    @Override
    public synchronized void addComposited( Map map ) throws IllegalArgumentException
    {
        super.addComposited( map );
        this.maps.addLast( map );
    }



    @Override
    public synchronized Map removeComposited( Map map )
    {
        Map removed = super.removeComposited( map );
        this.maps.remove( map );
        return removed;
    }



    /** 
     * Starts a new scope. 
     * All items added in the session before the previous session are removed.
     * All items added in the previous scope are still retrievable and removable.
     */ 
    public void next()
    {
        removeComposited( this.maps.getFirst() );
        addComposited( new HashMap() );
    }

    public Object put( CompositeMap map, Map[] composited, Object key, Object value )
    {
        if(composited.length < 1)
        {
            throw new UnsupportedOperationException("No composites to add elements to");
        }
        Object result = map.get( key );
        if(result != null)
        {
            map.remove( key );
        }
        composited[composited.length-1].put( key, value );
        return result;
    }

    public void putAll( CompositeMap map, Map[] composited, Map mapToAdd )
    {
        for(Entry entry: (Set<Entry>)mapToAdd.entrySet())
        {
            put(map, composited, entry.getKey(), entry.getValue());
        }
    }

    public void resolveCollision( CompositeMap composite, Map existing, Map added, Collection intersect )
    {
        existing.keySet().removeAll( intersect );       
    }

    @Override
    public String toString()
    {
        return new HashMap(this).toString();
    }


}

Usage:

用法：

@RequestMapping(value="/login.do", method=RequestMethod.POST)
    public ModelAndView login(@Valid User user){
        ModelAndView mv = new ModelAndView("redirect:result.html");
        if (authService.authenticate(user.getUserName(), user.getPassword()))
            mv.addObject("flashScope.message", "Success");
        //else
            mv.addObject("flashScope.message", "Login Failed");
        return mv;
    }

@RequestMapping(value ="/result.html", method=RequestMethod.GET)
    public ModelAndView result(){
        ModelAndView mv = new ModelAndView("login/loginAction");
        return mv;
    }

In JSP the usage is very simple:

在 JSP 中，用法非常简单：

${flashScope.message}

In addition you need to configure FlashScopeInterceptor class as interceptor.

此外，您需要将 FlashScopeInterceptor 类配置为拦截器。

<bean id="flashScopeInterceptor" class="x.y.z.FlashScopeInterceptor" />
<bean id="handlerMapping" class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
  <property name="interceptors">
    <list><ref bean="flashScopeInterceptor"/></list>
  </property>
</bean> 

回答by Ralph

I recommend to have a look at the source code of org.springframework.web.context.request.SessionScope. This scope must have solved the same problem some how.

我建议查看org.springframework.web.context.request.SessionScope的源代码。这个范围一定以某种方式解决了同样的问题。

It looks like that they use: RequestContextHolder.currentRequestAttributes().getSessionId()

看起来他们使用： RequestContextHolder.currentRequestAttributes().getSessionId()

回答by Kostya Osipov

You can get access to session attributes using the next code within your scope class methods in Spring MVC (works in 3.2):

您可以使用 Spring MVC 中作用域类方法中的下一个代码访问会话属性（适用于 3.2）：

RequestAttributes attributes = RequestContextHolder.currentRequestAttributes();
attributes.getAttribute("some key", NativeWebRequest.SCOPE_SESSION);
attributes.setAttribute("some key", YouObject, NativeWebRequest.SCOPE_SESSION);

RequestAttributes implementation (ServletRequestAttributes) internally will call set/getAttribute() methods on current session object.

RequestAttributes 实现 (ServletRequestAttributes) 将在内部调用当前会话对象上的 set/getAttribute() 方法。