1：责任链模式概述
《设计模式》中给它的定义如下：使多个对象都有机会处理请求，从而避免请求的发送者和接收者之间的耦合关系，将这些对象连成一条链，并沿着这条链来传递请求，直到有一个对象处理它为止。
从定义上可以看出，责任链模式的提出是为了“解耦”，以应变系统需求的变更和不明确性。
2：代码实现部分
2.1 Request类 代表一个请求类
package com.bjsxt.filter;
public class Request {
private String requestStr;
public String getRequestStr() {
return requestStr;
}
public void setRequestStr(String requestStr) {
this.requestStr = requestStr;
}
}
2.2 Response类 代表一个回复类
package com.bjsxt.filter;
public class Response {
private String responseStr;
public String getResponseStr() {
return responseStr;
}
public void setResponseStr(String responseStr) {
this.responseStr = responseStr;
}
}
2.3 Filter接口 代表一个请求处理接口
package com.bjsxt.filter;
public interface Filter {
public void doFilter(Request request, Response response, FilterChain chain);
}
2.4 HTMLFilter类 代表一个HTML的请求处理类
package com.bjsxt.filter;
public class HTMLFilter implements Filter {
@Override
public void doFilter(Request request, Response response, FilterChain chain) {
String requestStr = request.getRequestStr();
requestStr += "---HTMLFilter()";
request.setRequestStr(requestStr);
chain.doFilter(request, response, chain);
String responseStr = response.getResponseStr();
responseStr += "--HTMLFilterResponse";
response.setResponseStr(responseStr);
}
}
2.5 SesitiveFilter类 代表另外一个请求的处理类
package com.bjsxt.filter;
public class SesitiveFilter implements Filter {
@Override
public void doFilter(Request request, Response response, FilterChain chain) {
String requestStr = request.getRequestStr();
requestStr += "---SesitiveFilter()";
request.setRequestStr(requestStr);
chain.doFilter(request, response, chain);
String responseStr = response.getResponseStr();
responseStr += "--SesitiveFilterResponse";
response.setResponseStr(responseStr);
}
}
2.6 FilterChain类 代表一个Filter的链式容器类
package com.bjsxt.filter;
import java.util.ArrayList;
import java.util.List;
public class FilterChain implements Filter {
private List<Filter> filters = new ArrayList<Filter>();
private int index = 0;
public FilterChain addFilter(Filter filter) {
this.filters.add(filter);
return this;
}
@Override
public void doFilter(Request request, Response response, FilterChain chain) {
if(index == filters.size()) {
return ;
}
Filter filter = filters.get(this.index);
this.index++;
filter.doFilter(request, response, chain);
}
}
2.7 Main类 测试类
package com.bjsxt.filter;
public class Main {
public static void main(String[] args) {
Request request = new Request();
request.setRequestStr("request");
Response response = new Response();
response.setResponseStr("response");
FilterChain chain = new FilterChain();
chain.addFilter(new HTMLFilter()).addFilter(new SesitiveFilter());
chain.doFilter(request, response, chain);
System.out.println(request.getRequestStr());
System.out.println(response.getResponseStr());
}
}
2.8 输出结果
request---HTMLFilter()---SesitiveFilter()
response--SesitiveFilterResponse--HTMLFilterResponse