攔截過濾器模式
攔截過濾器模式（Intercepting Filter Pattern）用于對應(yīng)用程序的請求或響應(yīng)做一些預(yù)處理/后處理。定義過濾器，并在把請求傳給實(shí)際目標(biāo)應(yīng)用程序之前應(yīng)用在請求上。過濾器可以做認(rèn)證/授權(quán)/記錄日志，或者跟蹤請求，然后把請求傳給相應(yīng)的處理程序。以下是這種設(shè)計(jì)模式的實(shí)體。
- 過濾器（Filter） - 過濾器在請求處理程序執(zhí)行請求之前或之后，執(zhí)行某些任務(wù)。
- 過濾器鏈（Filter Chain） - 過濾器鏈帶有多個(gè)過濾器，并在 Target 上按照定義的順序執(zhí)行這些過濾器。
- Target - Target 對象是請求處理程序。
- 過濾管理器（Filter Manager） - 過濾管理器管理過濾器和過濾器鏈。
- 客戶端（Client） - Client 是向 Target 對象發(fā)送請求的對象。
實(shí)現(xiàn)
我們將創(chuàng)建 FilterChain、FilterManager、Target、Client 作為表示實(shí)體的各種對象。AuthenticationFilter 和 DebugFilter 表示實(shí)體過濾器。
InterceptingFilterDemo，我們的演示類使用 Client 來演示攔截過濾器設(shè)計(jì)模式。
步驟 1
創(chuàng)建過濾器接口 Filter。
Filter.java
<pre class="prettyprint" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">public interface Filter {
public void execute(String request);
}
</pre>
步驟 2
創(chuàng)建實(shí)體過濾器。
AuthenticationFilter.java
<pre class="prettyprint" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">public class AuthenticationFilter implements Filter {
public void execute(String request){
System.out.println("Authenticating request: " + request);
}
}
</pre>
DebugFilter.java
<pre class="prettyprint" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">public class DebugFilter implements Filter {
public void execute(String request){
System.out.println("request log: " + request);
}
}
</pre>
步驟 3
創(chuàng)建 Target。
Target.java
<pre class="prettyprint" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">public class Target {
public void execute(String request){
System.out.println("Executing request: " + request);
}
}
</pre>
步驟 4
創(chuàng)建過濾器鏈。
FilterChain.java
<pre class="prettyprint" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">import java.util.ArrayList;
import java.util.List;
public class FilterChain {
private List filters = new ArrayList();
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;
}
}
</pre>
步驟 5
創(chuàng)建過濾管理器。
FilterManager.java
<pre class="prettyprint" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">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);
}
}
</pre>
步驟 6
創(chuàng)建客戶端 Client。
Client.java
<pre class="prettyprint" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">public class Client {
FilterManager filterManager;
public void setFilterManager(FilterManager filterManager){
this.filterManager = filterManager;
}
public void sendRequest(String request){
filterManager.filterRequest(request);
}
}
</pre>
步驟 7
使用 Client 來演示攔截過濾器設(shè)計(jì)模式。
InterceptingFilterDemo.java
<pre class="prettyprint" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">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");
}
}
</pre>
步驟 8
驗(yàn)證輸出。
<pre class="result" style="margin: 15px 0px; padding: 10px 5px; position: relative; width: auto; max-width: 700px; box-sizing: border-box; display: block; line-height: 1.7; background: rgb(239, 239, 239); border-radius: 3px; font-size: 14px; font-family: Consolas, "Courier New", Courier, monospace; overflow-x: auto; border: 1px solid rgb(221, 221, 221); overflow-wrap: break-word !important; white-space: pre-wrap !important; color: rgb(51, 51, 51); font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration-style: initial; text-decoration-color: initial;">Authenticating request: HOME
request log: HOME
Executing request: HOME</pre>
