项目应用：web项目从拦截请求获取用户

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
*/
@Override
public boolean supportsParameter(MethodParameter parameter) {
return parameter.getParameterAnnotation(UserVo.class) != null;
}

@Override
public 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.xx.xx.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>