责任链模式的两个简单demo

文章目录

过滤字符手写HttpServletFilter 责任链模式的核心是：过滤器链【注意：递归算法的运用】

过滤字符

当不满足条件时，则停止过滤

/** * @author LiuWei * @date 2020/10/5 * @description */ public class MainDemo { public static void main(String[] args) { Msg msg = new Msg(); msg.setMsg("我喜欢<font color='red'>体育、代码、美食、美女等</font>"); FirstFilter firstFilter = new FirstFilter(); SecondFilter secondFilter = new SecondFilter(); ThirdFilter thirdFilter = new ThirdFilter(); FourthFilter fourthFilter = new FourthFilter(); ChainFilter chainFilter1 = new ChainFilter(); ChainFilter chainFilter2 = new ChainFilter(); chainFilter1.add(firstFilter).add(secondFilter); chainFilter2.add(thirdFilter).add(fourthFilter); //把过滤器链2放入过滤器链1 chainFilter1.add(chainFilter2); chainFilter1.doFilter(msg); System.out.println(msg.getMsg()); } } class Msg { private Integer id; private String msg; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getMsg() { return msg; } public void setMsg(String msg) { this.msg = msg; } @Override public String toString() { return JSONObject.toJSONString(this); } } interface Filter { boolean doFilter(Msg msg); } /** * 过滤链 * 亮点1：过滤器链实现Filter接口时，当两个过滤器链组合放到一个数组，执行doFilter会发生递归调用 * 亮点2：当doFilter返回false时，停止往下执行，直接返回，这里也存在递归 */ class ChainFilter implements Filter { List<Filter> filters = new ArrayList<>(); public ChainFilter add(Filter filter) { filters.add(filter); return this; } @Override public boolean doFilter(Msg msg) { for (Filter filter : filters) { if (!filter.doFilter(msg)) { return false; } } return true; } } class FirstFilter implements Filter { @Override public boolean doFilter(Msg msg) { System.out.println(this.getClass().getSimpleName()); msg.setMsg(msg.getMsg().replace("<", "[").replace(">", "]")); return true; } } class SecondFilter implements Filter { @Override public boolean doFilter(Msg msg) { System.out.println(this.getClass().getSimpleName()); if (msg.getMsg().contains("编程")) { return false; } return true; } } class ThirdFilter implements Filter { @Override public boolean doFilter(Msg msg) { System.out.println(this.getClass().getSimpleName()); msg.setMsg(msg.getMsg().replace("美女", "女神")); return true; } } class FourthFilter implements Filter { @Override public boolean doFilter(Msg msg) { System.out.println(this.getClass().getSimpleName()); msg.setMsg(msg.getMsg().replace("体育", "运动")); return true; } }

手写HttpServletFilter

需求：请求时按顺序先后进过FirstFilter，SecondFilter ，响应时再按顺序先后经过SecondFilter、FirstFilter，请求经过任何一个过滤器中如果不满足条件，则返回响应对象，此响应对象也会进过已经进过的过滤器

/** * @author LiuWei * @date 2020/10/5 * @description */ public class mainDemo { public static void main(String[] args) { Request request = new Request(); request.setStr("用户请求："); Response response = new Response(); response.setStr("响应结果："); FirstFilter firstFilter = new FirstFilter(); SecondFilter secondFilter = new SecondFilter(); FilterChain filterChain = new FilterChain(); filterChain.add(firstFilter).add(secondFilter); filterChain.doFilter(request, response); System.out.println(request.getStr()); System.out.println(response.getStr()); } } /** * 因为这里模拟了响应对象，因此doFilter方法不需要返回值，响应结果直接保存在响应对象中 */ interface Filter { void doFilter(Request request, Response response, FilterChain filterChain); } /** * 责任链模式的核心是：过滤器链对递归的运用 */ class FilterChain { private List<Filter> filters = new ArrayList<>(); private Iterator<Filter> iterator; public FilterChain add(Filter filter) { filters.add(filter); return this; } /** * 请求每进入过滤器执行doFilter时，都会通过FilterChain过滤器判断是否是最后一个过滤器， * 如果还有过滤器，则调用下一个过滤器继续过滤请求，直到没有过滤器,直接返回。 * 当最后一个过滤器过滤完请求，通过FilterChain判断没有过滤器了，才会开始一层一层的过滤响应 * 一个Filter的doFilter方法的实现逻辑：过滤请求的代码--》过滤器链的代码--》过绿请求的代码 * 过滤器链调用doFilter方法实际上是一种递归算法 */ public void doFilter(Request request, Response response) { if (iterator == null) { iterator = filters.iterator(); } while (iterator.hasNext()) { Filter filter = iterator.next(); filter.doFilter(request, response, this); } } } class FirstFilter implements Filter { @Override public void doFilter(Request request, Response response, FilterChain filterChain) { request.setStr(request.getStr() + "--request经过FirstFilter"); if (!request.getStr().contains("用户")) { response.setStr(response.getStr() + "--FirstFilter没有找到相应的字符：用户"); } filterChain.doFilter(request, response); response.setStr(response.getStr() + "--response经过FirstFilter"); } } class SecondFilter implements Filter { @Override public void doFilter(Request request, Response response, FilterChain filterChain) { request.setStr(request.getStr() + "--request经过SecondFilter"); if (!request.getStr().contains("请求")) { response.setStr(response.getStr() + "--SecondFilter没有找到相应的字符：请求"); return; } filterChain.doFilter(request, response); response.setStr(response.getStr() + "--response经过SecondFilter"); } } class Request { private String str; public String getStr() { return str; } public void setStr(String str) { this.str = str; } @Override public String toString() { return JSONObject.toJSONString(this); } } class Response { private String str; public String getStr() { return str; } public void setStr(String str) { this.str = str; } @Override public String toString() { return JSONObject.toJSONString(this); } }