桥接模式
亦称： Bridge
1. 简介
桥接模式是一种结构型设计模式，可将一个大类或一系列紧密相关的类拆分为抽象和实现两个独立的层次结构, 从而能在开发时分别使用。桥接模式的主要作用就是通过将抽象部分与实现部分分离，把多种可匹配的使用进行组合。说白了核心实现也就是在A类中含有B类接口，通过构造函数传递B类的实现，这个B类就是设计的桥。
2. 模拟场景
需要实现多支付与多模式的融合使用，如果给每一个支付都实现一次不同的模式，即使是继承类也需要开发好多。而且随着后面接入了更多的支付服务或者支付方式，就会呈爆炸似的扩展。因为在这些组合中如果每一个类都实现不同的服务可能会出现笛卡尔积，而使用桥接模式就可以非常简单。
3. 解决方案
3.1 桥接模式模型结构
3.2 支付类型桥接抽象类
java
public abstract class Pay {
protected Logger logger = LoggerFactory.getLogger(Pay.class);
protected IPayMode payMode;
public Pay(IPayMode payMode) {
this.payMode = payMode;
}
public abstract String transfer(String uId, String tradeId, BigDecimal amount);
}在这个类中定义了支付方式的需要实现的划账接口：transfer，以及桥接接口：IPayMode，并在构造函数中用户方自行选择支付方式。如果没有接触过此类实现，可以重点关注IPayMode payMode，这部分是桥接的核心。
java
public class WxPay extends Pay {
public WxPay(IPayMode payMode) {
super(payMode);
}
public String transfer(String uId, String tradeId, BigDecimal amount) {
logger.info("模拟微信渠道支付划账开始。uId：{} tradeId：{} amount：{}", uId, tradeId, amount);
boolean security = payMode.security(uId);
logger.info("模拟微信渠道支付风控校验。uId：{} tradeId：{} security：{}", uId, tradeId, security);
if (!security) {
logger.info("模拟微信渠道支付划账拦截。uId：{} tradeId：{} amount：{}", uId, tradeId, amount);
return "0001";
}
logger.info("模拟微信渠道支付划账成功。uId：{} tradeId：{} amount：{}", uId, tradeId, amount);
return "0000";
}
}
java
public class ZfbPay extends Pay {
public ZfbPay(IPayMode payMode) {
super(payMode);
}
public String transfer(String uId, String tradeId, BigDecimal amount) {
logger.info("模拟支付宝渠道支付划账开始。uId：{} tradeId：{} amount：{}", uId, tradeId, amount);
boolean security = payMode.security(uId);
logger.info("模拟支付宝渠道支付风控校验。uId：{} tradeId：{} security：{}", uId, tradeId, security);
if (!security) {
logger.info("模拟支付宝渠道支付划账拦截。uId：{} tradeId：{} amount：{}", uId, tradeId, amount);
return "0001";
}
logger.info("模拟支付宝渠道支付划账成功。uId：{} tradeId：{} amount：{}", uId, tradeId, amount);
return "0000";
}
}
boolean security(String uId);
}
txt
任何一个支付模式：刷脸、指纹、密码，都会过不同程度的安全风控，这里定义一个安全校验接口。
### 3.4 三种支付模式风控(刷脸、指纹、密码)
<div class="vp-code-group"><div class="tabs"><input type="radio" name="cg48" id="cg48-0" checked><label for="cg48-0">刷脸</label><input type="radio" name="cg48" id="cg48-1"><label for="cg48-1">指纹</label><input type="radio" name="cg48" id="cg48-2"><label for="cg48-2">密码</label></div><div class="blocks"><div class="language-java vp-adaptive-theme"><span class="lang">java</span><pre class="shiki language-java"><code><span class="line"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title class_">PayFaceMode</span> <span class="hljs-keyword">implements</span> <span class="hljs-title class_">IPayMode</span>{
</span>
<span class="line">
</span>
<span class="line"> <span class="hljs-keyword">protected</span> <span class="hljs-type">Logger</span> <span class="hljs-variable">logger</span> <span class="hljs-operator">=</span> LoggerFactory.getLogger(PayCypher.class);
</span>
<span class="line">
</span>
<span class="line"> <span class="hljs-keyword">public</span> <span class="hljs-type">boolean</span> <span class="hljs-title function_">security</span><span class="hljs-params">(String uId)</span> {
</span>
<span class="line"> logger.info(<span class="hljs-string">"人脸支付，风控校验脸部识别"</span>);
</span>
<span class="line"> <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
</span>
<span class="line"> }
</span>
<span class="line">}
</span></code></pre></div><div class="language-java vp-adaptive-theme"><span class="lang">java</span><pre class="shiki language-java"><code><span class="line"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title class_">PayFingerprintMode</span> <span class="hljs-keyword">implements</span> <span class="hljs-title class_">IPayMode</span>{
</span>
<span class="line">
</span>
<span class="line"> <span class="hljs-keyword">protected</span> <span class="hljs-type">Logger</span> <span class="hljs-variable">logger</span> <span class="hljs-operator">=</span> LoggerFactory.getLogger(PayCypher.class);
</span>
<span class="line">
</span>
<span class="line"> <span class="hljs-keyword">public</span> <span class="hljs-type">boolean</span> <span class="hljs-title function_">security</span><span class="hljs-params">(String uId)</span> {
</span>
<span class="line"> logger.info(<span class="hljs-string">"指纹支付，风控校验指纹信息"</span>);
</span>
<span class="line"> <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
</span>
<span class="line"> }
</span>
<span class="line">}
</span></code></pre></div><div class="language-java vp-adaptive-theme"><span class="lang">java</span><pre class="shiki language-java"><code><span class="line"><span class="hljs-keyword">public</span> <span class="hljs-keyword">class</span> <span class="hljs-title class_">PayCypher</span> <span class="hljs-keyword">implements</span> <span class="hljs-title class_">IPayMode</span>{
</span>
<span class="line">
</span>
<span class="line"> <span class="hljs-keyword">protected</span> <span class="hljs-type">Logger</span> <span class="hljs-variable">logger</span> <span class="hljs-operator">=</span> LoggerFactory.getLogger(PayCypher.class);
</span>
<span class="line">
</span>
<span class="line"> <span class="hljs-keyword">public</span> <span class="hljs-type">boolean</span> <span class="hljs-title function_">security</span><span class="hljs-params">(String uId)</span> {
</span>
<span class="line"> logger.info(<span class="hljs-string">"密码支付，风控校验环境安全"</span>);
</span>
<span class="line"> <span class="hljs-keyword">return</span> <span class="hljs-literal">true</span>;
</span>
<span class="line"> }
</span>
<span class="line">}
</span></code></pre></div></div></div>
### 3.5 编写测试类验证
```java
@Test
public void test_pay() {
System.out.println("\r\n模拟测试场景：微信支付、人脸方式。");
Pay wxPay = new WxPay(new PayFaceMode());
wxPay.transfer("weixin_1092033111", "100000109893", new BigDecimal(100));
System.out.println("\r\n模拟测试场景：支付宝支付、指纹方式。");
Pay zfbPay = new ZfbPay(new PayFingerprintMode());
zfbPay.transfer("jlu19dlxo111","100000109894",new BigDecimal(100));
}
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