当我们想要对应用程序的请求或响应进行一些预处理/后处理时,使用拦截过滤器设计模式.在将请求传递给实际目标应用程序之前,会在请求上定义和应用过滤器.过滤器可以执行身份验证/授权/记录或跟踪请求,然后将请求传递给相应的处理程序.以下是此类设计模式的实体.
过滤器 - 将执行的过滤器请求处理程序执行请求之前或之后的某个任务.
过滤器链 - 过滤器链带有多个过滤器并帮助执行它们按目标定义的顺序.
目标 - 目标对象是请求处理程序
过滤器管理器 - 过滤器管理器管理过滤器和过滤器链.
客户端 - 客户是向Target对象发送请求的对象.
我们将创建一个 FilterChain , FilterManager ,目标,客户端作为代表我们实体的各种对象. AuthenticationFilter 和 DebugFilter 代表具体的过滤器.
InterceptingFilterDemo ,我们的演示类,将使用 Client 展示拦截过滤器设计模式.
创建过滤器界面.
Filter.java
public interface Filter { public void execute(String request); }
创建具体过滤器.
AuthenticationFilter.java
public class AuthenticationFilter implements Filter { public void execute(String request){ System.out.println("Authenticating request: " + request); } }
DebugFilter.java
public class DebugFilter implements Filter { public void execute(String request){ System.out.println("request log: " + request); } }
创建目标
Target.java
public class Target { public void execute(String request){ System.out.println("Executing request: " + request); } }
创建过滤器链
FilterChain.java
import java.util.ArrayList; import java.util.List; public class FilterChain { private List<Filter> filters = new ArrayList<Filter>(); private Target target; public void addFilter(Filter filter){ filters.add(filter); } public void execute(String request){ for (Filter filter : filters) { filter.execute(request); } target.execute(request); } public void setTarget(Target target){ this.target = target; } }
创建过滤器管理器
FilterManager.java
public class FilterManager { FilterChain filterChain; public FilterManager(Target target){ filterChain = new FilterChain(); filterChain.setTarget(target); } public void setFilter(Filter filter){ filterChain.addFilter(filter); } public void filterRequest(String request){ filterChain.execute(request); } }
创建客户
Client.java
public class Client { FilterManager filterManager; public void setFilterManager(FilterManager filterManager){ this.filterManager = filterManager; } public void sendRequest(String request){ filterManager.filterRequest(request); } }
使用客户端演示拦截过滤器设计模式.
InterceptingFilterDemo.java
public class InterceptingFilterDemo { public static void main(String[] args) { FilterManager filterManager = new FilterManager(new Target()); filterManager.setFilter(new AuthenticationFilter()); filterManager.setFilter(new DebugFilter()); Client client = new Client(); client.setFilterManager(filterManager); client.sendRequest("HOME"); } }
验证输出.
Authenticating request: HOME request log: HOME Executing request: HOME