项目应用：建立解释器完成对用户的获取

首选说下要求背景，用户通过网站登录后会将用户的基本信息记录在session，而当有请求需要用到用户信息的时候，每个方法都需要自己从session中拉取用户信息，而获取不到时还需要去处理跳转登录的操作，十分麻烦。因此考虑到开发的方便性，希望可以用到注解的方式直接将用户信息封装好，作为参数传递给各个请求。

首先有个用户的Vo类

public class UserVO {  private int id=0;private String ticket=""; //唯一证书private String username=""; //用户名private String nickname="";//昵称private String avatar="";//头像private int gender=0;// 性别private String phone="";//电话private String  email="";//邮箱private int  role=0;//用户权限//认证信息private String access_token="";private String refresh_token=""; private Integer expires_in=0;public String getUsername() {return username;}public void setUsername(String username) {this.username = username;} public String getNickname() {return nickname;}public void setNickname(String nickname) {this.nickname = nickname;}public String getAvatar() {return avatar;}public void setAvatar(String avatar) {this.avatar = avatar;}public int getGender() {return gender;}public void setGender(int gender) {this.gender = gender;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}        public String getTicket() {                return ticket;        }        public void setTicket(String ticket) {                this.ticket = ticket;        }public int getId() {return id;}public void setId(int id) {this.id = id;} public String getAccess_token() {return access_token;}public void setAccess_token(String access_token) {this.access_token = access_token;}public String getRefresh_token() {return refresh_token;}public void setRefresh_token(String refresh_token) {this.refresh_token = refresh_token;}public Integer getExpires_in() {return expires_in;}public void setExpires_in(Integer expires_in) {this.expires_in = expires_in;}public int getRole() {return role;}public void setRole(int role) {this.role = role;} }

建立个参数级的注解，用于注入用户信息

@Target({ElementType.PARAMETER})  @Retention(RetentionPolicy.RUNTIME)  @Documented  public @interface UserVo {/** * The URI template variable to bind to. */String value() default "";}

建立解释器从session中获得用户

public class UserArgumentResolver implements HandlerMethodArgumentResolver{/** * 定义解释器支持解析的参数 */@Overridepublic boolean supportsParameter(MethodParameter parameter) {return parameter.getParameterAnnotation(UserVo.class) != null;  }@Overridepublic UserVO resolveArgument(MethodParameter parameter,        ModelAndViewContainer mavContainer, NativeWebRequest webRequest,        WebDataBinderFactory binderFactory) throws Exception {        HttpServletRequest request= (HttpServletRequest) webRequest.getNativeRequest();        //从session中获取用户信息        UserVO userInfo=(UserVO)request.getSession().getAttribute("userInfo");        return userInfo;    }}

最后在xml中加入解释器

    <mvc:annotation-driven>        <mvc:argument-resolvers>            <!-- 自定义标签获得UserVO-->             <bean class="com.xiaoma.universe.common.interceptor.UserArgumentResolver" />        </mvc:argument-resolvers>  </mvc:annotation-driven>

配合拦截器一起使用，当请求发生的时候先进入拦截器判断session中的用户信息是否为null，不为空进入解释器获取，为空直接进入登录页面

定义拦截器：

public class UserInterceptor implements HandlerInterceptor{  @Override  public void afterCompletion(HttpServletRequest request,  HttpServletResponse response, Object obj, Exception err)  throws Exception {  }  @Override  public void postHandle(HttpServletRequest request, HttpServletResponse response,  Object obj, ModelAndView mav) throws Exception {  }  @Override  public boolean preHandle(HttpServletRequest request, HttpServletResponse response,  Object obj) throws Exception {  HttpSession session = request.getSession();UserVO userInfo = (UserVO) session.getAttribute("userInfo");String url = request.getRequestURI();if((userInfo==null){//不符合条件的，跳转到登录界面 response.sendRedirect("/login");return false;  }request.setAttribute("userInfo", userInfo);return true;  }  }  

xml中配置拦截规则

<mvc:interceptors><mvc:interceptor><mvc:mapping path="/*"/><bean class="xx.xx.xx.UserInterceptor"></bean></mvc:interceptor></mvc:interceptors>