Spring过滤器和拦截器的区别
两者的作用
过滤器：
是在javaweb中，你传入的request、response提前过滤掉一些信息，或者提前设置一些参数，然后再传入servlet或者struts的action进行业务逻辑，比如过滤掉非法url（不是login.do的地址请求，如果用户没有登陆都过滤掉），或者在传入servlet或者 struts的action前统一设置字符集，或者去除掉一些非法字符.。
拦截器 ：
是在面向切面编程的就是在你的service或者一个方法，前调用一个方法，或者在方法后调用一个方法比如动态代理就是拦截器的简单实现，在你调用方法前打印出字符串（或者做其它业务逻辑的操作），也可以在你调用方法后打印出字符串，甚至在你抛出异常的时候做业务逻辑的操作。
从具体实现区分
1. 过滤器是servlet的
2. 拦截器是spring aop的
细节区别
①拦截器是基于Java的反射机制的，而过滤器是基于函数回调。
②拦截器不依赖于servlet容器，过滤器依赖于servlet容器。
③拦截器只能对action请求起作用，而过滤器则可以对几乎所有的请求起作用。
④拦截器可以访问action上下文、值栈里的对象，而过滤器不能访问。
⑤在action的生命周期中，拦截器可以多次被调用，而过滤器只能在容器初始化时被调用一次。
⑥拦截器可以获取IOC容器中的各个bean，而过滤器就不行，这点很重要，在拦截器里注入一个service，可以调用业务逻辑。
工作流程及顺序
应用场景
1. 对于一些不需要用到bean的request预处理和response后处理，可以过滤器，如：encoding，cors
2. 对于一些要用到用到bean，或者逻辑比较复杂，有特殊处理的，可以用拦截器
3. 不过不怕麻烦，也可以自己建AOP
代码实现
拦截器：
继承spring的HandlerInterceptorAdapter
package com.cherrypicks.hsbcpayme.api.interceptor;
import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.math.NumberUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
import com.cherrypicks.hsbcpayme.api.vo.UserSessionVO;
import com.cherrypicks.hsbcpayme.exception.InvalidArgumentException;
import com.cherrypicks.hsbcpayme.exception.InvalidUserSessionException;
import com.cherrypicks.hsbcpayme.service.UserSessionService;
import com.cherrypicks.hsbcpayme.util.Constants;
import com.cherrypicks.hsbcpayme.util.URLAnalysis;
public class SessionInterceptor extends HandlerInterceptorAdapter {
private static ThreadLocal<UserSessionVO> threadLocal = new ThreadLocal<UserSessionVO>();
private final Logger logger = LoggerFactory.getLogger(this.getClass());
@Autowired
private UserSessionService userSessionService;
@PostConstruct
public void init() {
logger.info("init");
}
@PreDestroy
public void destroy() {
logger.info("destroy");
}
@Override
public boolean preHandle(final HttpServletRequest request, final HttpServletResponse response, final Object handler) throws Exception {
logger.debug("SessionInterceptor.preHandle run....");
final URLAnalysis urlAnalysis = (URLAnalysis) request.getAttribute(Constants.URL_ANALYSIS);
final String userIdString = urlAnalysis.getParam(Constants.USERID);
final String accessToken = urlAnalysis.getParam(Constants.ACCESSTOKEN);
if (!StringUtils.isNotEmpty(userIdString)) {
throw new InvalidArgumentException("userId is required");
}
if (!StringUtils.isNotEmpty(accessToken)) {
throw new InvalidArgumentException("accessToken is required");
}
if (!NumberUtils.isNumber(userIdString)) {
throw new InvalidArgumentException("userId[" + userIdString + "] invalid");
}
final boolean result = userSessionService.checkLogin(Long.valueOf(userIdString), accessToken);
if (!result) {
throw new InvalidUserSessionException("Invalid accessToken[" + accessToken + "]");
}
final UserSessionVO userSessionVO = new UserSessionVO();
userSessionVO.setUserId(Long.valueOf(userIdString));
userSessionVO.setAccessToken(accessToken);
threadLocal.set(userSessionVO);
return result;
}
@Override
public void afterCompletion(final HttpServletRequest request, final HttpServletResponse response, final Object handler, final Exception ex) throws Exception {
logger.debug("SessionInterceptor.afterCompletion run....");
final UserSessionVO userSessionVO = threadLocal.get();
if (userSessionVO != null) {
// renewal session
userSessionService.renewalSessoin(userSessionVO.getUserId(), userSessionVO.getAccessToken());
}
threadLocal.remove();
}
}
过滤器：
继承java的Filter，其实现是servlet
package com.cherrypicks.hsbcpayme.api.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.http.HttpStatus;
import com.cherrypicks.hsbcpayme.util.Constants;
public class CorsFilter implements Filter {
// private final Log logger = LogFactory.getLog(this.getClass());
private final String allowedOrigins;
private final String allowCredentials;
public CorsFilter(final String allowedOrigins, final String allowCredentials) {
this.allowedOrigins = allowedOrigins;
this.allowCredentials = allowCredentials;
}
@Override
public void init(final FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(final ServletRequest req, final ServletResponse res, final FilterChain chain) throws IOException, ServletException {
final HttpServletRequest request = (HttpServletRequest) req;
final HttpServletResponse response = (HttpServletResponse) res;
final String method = request.getMethod();
// this origin value could just as easily have come from a database
response.setHeader("Access-Control-Allow-Origin", allowedOrigins);
response.setHeader("Access-Control-Allow-Methods", "GET, HEAD, POST, PUT, DELETE, OPTIONS");
response.setHeader("Access-Control-Max-Age", "3600");
response.setHeader("Access-Control-Allow-Credentials", allowCredentials);
// "Content-Type, X-Requested-With, accept, Origin, Access-Control-Request-Method, Access-Control-Request-Headers"
response.setHeader("Access-Control-Allow-Headers", "Origin,Accept,X-Requested-With,Content-Type,Access-Control-Request-Method,Access-Control-Request-Headers,Authorization," + Constants.SESSIONID + "," + Constants.CSRFTOKEN);
if ("OPTIONS".equals(method)) {
response.setStatus(HttpStatus.OK.value());
} else {
chain.doFilter(req, res);
}
}
@Override
public void destroy() {
}
}