項目中調用service層方法

使用的工具類

package com.fltd.tourism.util;

import java.util.Locale;
import java.util.Map;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.stereotype.Component;

@Component
public class SpringContextUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext = null;

    public void setApplicationContext(ApplicationContext context) throws BeansException {
        applicationContext = context;
    }

    /**
     * 獲取applicationContext對象
     * 
     * @return
     */
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name) {
        return (T) applicationContext.getBean(name);
    }

    public static <T> T getBean(Class<T> clazz) {
        System.out.println(applicationContext);
        return applicationContext.getBean(clazz);
    }

    /**
     * 根據bean的id來查找對�?
     * 
     * @param id
     * @return
     */

    @SuppressWarnings("unchecked")
    public static <T> T getBeanById(String id) {
        return (T) applicationContext.getBean(id);
    }

    /**
     * 根據bean的class來查找對�?
     * 
     * @param c
     * @return
     */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static <T> T getBeanByClass(Class c) {
        return (T) applicationContext.getBean(c);
    }

    /**
     * 根據bean的class來查找所有的對象(包括子類)
     * 
     * @param c
     * @return
     */
    @SuppressWarnings({ "unchecked", "rawtypes" })
    public static Map getBeansByClass(Class c) {
        return applicationContext.getBeansOfType(c);
    }

    public static String getMessage(String key) {
        return applicationContext.getMessage(key, null, Locale.getDefault());
    }

}

使用方法：

SpringContextUtil.getBean(xxxService.class).xxxmethod();

或者使用

在項目中遇到一個問題，在 Filter中注入 Serivce失敗，注入的service始終為null。如下所示：

 1 public class WeiXinFilter implements Filter{
 2     
 3     @Autowired
 4     private UsersService usersService;
 5 
 6     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
 7         HttpServletRequest req = (HttpServletRequest)request;
 8         HttpServletResponse resp = (HttpServletResponse)response;
 9 　　　　 Users users = this.usersService.queryByOpenid(openid);
10 }

上面的 usersService 會報空指針異常。

解決方法一：

 1 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
 2         HttpServletRequest req = (HttpServletRequest)request;
 3         HttpServletResponse resp = (HttpServletResponse)response;
 4         ServletContext sc = req.getSession().getServletContext();
 5         XmlWebApplicationContext cxt = (XmlWebApplicationContext)WebApplicationContextUtils.getWebApplicationContext(sc);
 6         
 7         if(cxt != null && cxt.getBean("usersService") != null && usersService == null)
 8             usersService = (UsersService) cxt.getBean("usersService");
 9         
10         Users users = this.usersService.queryByOpenid(openid);

解決方法二：

public class WeiXinFilter implements Filter{
    
    private UsersService usersService;
    
    public void init(FilterConfig fConfig) throws ServletException {
        ServletContext sc = fConfig.getServletContext(); 
        XmlWebApplicationContext cxt = (XmlWebApplicationContext)WebApplicationContextUtils.getWebApplicationContext(sc);
        
        if(cxt != null && cxt.getBean("usersService") != null && usersService == null)
            usersService = (UsersService) cxt.getBean("usersService");        
    }

相關原理：

1. 如何獲取 ServletContext：

1）在javax.servlet.Filter中直接獲取 
ServletContext context = config.getServletContext(); 

2）在HttpServlet中直接獲取 
this.getServletContext() 

3）在其他方法中，通過HttpServletRequest獲得 
request.getSession().getServletContext();

2. WebApplicationContext 與 ServletContext (轉自：http://blessht.iteye.com/blog/2121845)：

Spring的 ContextLoaderListener是一個實現了ServletContextListener接口的監聽器，在啟動項目時會觸發contextInitialized方法（該方法主要完成ApplicationContext對象的創建），在關閉項目時會觸發contextDestroyed方法（該方法會執行ApplicationContext清理操作）。

ConextLoaderListener加載Spring上下文的過程

①啟動項目時觸發contextInitialized方法，該方法就做一件事：通過父類contextLoader的initWebApplicationContext方法創建Spring上下文對象。

②initWebApplicationContext方法做了三件事：創建 WebApplicationContext；加載對應的Spring文件創建里面的Bean實例；將WebApplicationContext放入 ServletContext（就是Java Web的全局變量）中。

③createWebApplicationContext創建上下文對象，支持用戶自定義的上下文對象，但必須繼承自ConfigurableWebApplicationContext，而Spring MVC默認使用ConfigurableWebApplicationContext作為ApplicationContext（它僅僅是一個接口）的實 現。

④configureAndRefreshWebApplicationContext方法用 於封裝ApplicationContext數據並且初始化所有相關Bean對象。它會從web.xml中讀取名為 contextConfigLocation的配置，這就是spring xml數據源設置，然后放到ApplicationContext中，最后調用傳說中的refresh方法執行所有Java對象的創建。

⑤完成ApplicationContext創建之后就是將其放入ServletContext中，注意它存儲的key值常量。

解決方法三：

直接使用spring mvc中的HandlerInterceptor或者HandlerInterceptorAdapter 來替換Filter:

public class WeiXinInterceptor implements HandlerInterceptor {
    @Autowired
    private UsersService usersService;   
    
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        // TODO Auto-generated method stub
        return false;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
            throws Exception {
        // TODO Auto-generated method stub
        
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        // TODO Auto-generated method stub
        
    }
}

配置攔截路徑：

    <mvc:interceptors>
        <mvc:interceptor>
            <mvc:mapping path="/**" />
            <bean class="net.xxxx.interceptor.WeiXinInterceptor" />
        </mvc:interceptor>     
    </mvc:interceptors>

Filter 中注入 Service 的示例：

 1 public class WeiXinFilter implements Filter{    
 2     private UsersService usersService;    
 3     public void init(FilterConfig fConfig) throws ServletException {}
 4     public WeiXinFilter() {}
 5     public void destroy() {}
 6 
 7     public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
 8         HttpServletRequest req = (HttpServletRequest)request;
 9         HttpServletResponse resp = (HttpServletResponse)response;
10         
11         String userAgent = req.getHeader("user-agent");
12         if(userAgent != null && userAgent.toLowerCase().indexOf("micromessenger") != -1){    // 微信瀏覽器
13             String servletPath = req.getServletPath();
14             String requestURL = req.getRequestURL().toString();
15             String queryString = req.getQueryString();
16  
17             if(queryString != null){
18                 if(requestURL.indexOf("mtzs.html") !=-1 && queryString.indexOf("LLFlag")!=-1){
19                     req.getSession().setAttribute("LLFlag", "1");
20                     chain.doFilter(request, response);
21                     return;
22                 }
23             }
24             
25             String openidDES = CookieUtil.getValueByName("openid", req);
26             String openid = null;
27             if(StringUtils.isNotBlank(openidDES)){
28                 try {
29                     openid = DesUtil.decrypt(openidDES, "rxxxxxxxxxde");    // 解密獲得openid
30                 } catch (Exception e) {
31                     e.printStackTrace();
32                 }    
33             }
34             // ... ...
35             String[] pathArray = {"/weixin/enterAppFromWeiXin.json", "/weixin/getWeiXinUserInfo.json",
36                                     "/weixin/getAccessTokenAndOpenid.json", "/sendRegCode.json", "/register.json", 
37                                     "/login.json", "/logon.json", "/dump.json", "/queryInfo.json"};
38             List<String> pathList = Arrays.asList(pathArray);
39             
40             String loginSuccessUrl = req.getParameter("path");
41             String fullLoginSuccessUrl = "http://www.axxxxxxx.cn/pc/";
42             if(requestURL.indexOf("weixin_gate.html") != -1){
43                 req.getSession().setAttribute("loginSuccessUrl", loginSuccessUrl);
44 　　　　　　　　　　// ... ...
45             }
46             ServletContext sc = req.getSession().getServletContext();
47 XmlWebApplicationContext cxt = (XmlWebApplicationContext)WebApplicationContextUtils.getWebApplicationContext(sc);
48         
49             if(cxt != null && cxt.getBean("usersService") != null && usersService == null)
50                usersService = (UsersService) cxt.getBean("usersService");
51         
52             Users users = this.usersService.queryByOpenid(openid);
53             // ... ...
54             if(pathList.contains(servletPath)){    // pathList 中的訪問路徑直接 pass 
55                 chain.doFilter(request, response);
56                 return;
57             }else{
58                 if(req.getSession().getAttribute(CommonConstants.SESSION_KEY_USER) == null){ // 未登錄
59                     String llFlag = (String) req.getSession().getAttribute("LLFlag");
60                     if(llFlag != null && llFlag.equals("1")){    // 處理游客瀏覽
61                         chain.doFilter(request, response);
62                         return;
63                     }                  
64                     // ... ...// 3. 從騰訊服務器去獲得微信的 openid ,
65                     req.getRequestDispatcher("/weixin_gate.html").forward(request, response);
66                     return;
67                 }else{    // 已經登錄
68                     // 4. 已經登錄時的處理                    
69                     chain.doFilter(request, response); 
70                     return;
71                 }
72             }            
73         }else{    // 非微信瀏覽器
74             chain.doFilter(request, response);
75         }
76     }
77 
78 }