动态代理实现分库

src/main/java/top/fjy8018/designpattern/pattern/structural/proxy/dynamic/OrderServiceDynamicProxy.java

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+package top.fjy8018.designpattern.pattern.structural.proxy.dynamic;
+
+import lombok.extern.slf4j.Slf4j;
+import top.fjy8018.designpattern.pattern.structural.proxy.Order;
+import top.fjy8018.designpattern.pattern.structural.proxy.db.DataSourceContextHolder;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+
+/**
+ * 动态代理实现分库
+ * 动态代理适用场景更加广泛，可以实现通用分库逻辑
+ *
+ * @author F嘉阳
+ * @date 2020/3/3 11:00
+ */
+@Slf4j
+public class OrderServiceDynamicProxy implements InvocationHandler {
+
+    private Object target;
+
+    private static final String DB = "db";
+
+    public OrderServiceDynamicProxy(Object target) {
+        this.target = target;
+    }
+
+    /**
+     * 绑定目标对象
+     *
+     * @return
+     */
+    public Object bind() {
+        Class clazz = target.getClass();
+        return Proxy.newProxyInstance(clazz.getClassLoader(), clazz.getInterfaces(), this);
+    }
+
+    /**
+     * 代理
+     *
+     * @param proxy  代理对象，一般不调用该参数
+     * @param method 要被增强的方法对象
+     * @param args   方法参数
+     * @return
+     * @throws Throwable
+     */
+    @Override
+    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
+        // 参数传递
+        Object argObject = args[0];
+        beforeMethod(argObject);
+        // object是要被增强的方法的返回值
+        Object object = method.invoke(target, args);
+        afterMethod();
+        return object;
+    }
+
+    /**
+     * 前置增强方法
+     *
+     * @param args 方法参数
+     */
+    private void beforeMethod(Object args) {
+        int userId = 0;
+        // 对参数取模
+        log.info("动态代理，before code");
+        if (args instanceof Order) {
+            Order order = (Order) args;
+            userId = order.getUserId();
+        }
+        int dbRouter = userId % 2;
+        log.info("动态代理分配到【db{}】处理数据", dbRouter);
+
+        // 设置DataSource
+        DataSourceContextHolder.setDBType(DB + dbRouter);
+    }
+
+    private void afterMethod() {
+        log.info("动态代理after code");
+    }
+}

src/test/java/top/fjy8018/designpattern/pattern/structural/proxy/dynamic/OrderServiceDynamicProxyTest.java

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+package top.fjy8018.designpattern.pattern.structural.proxy.dynamic;
+
+import lombok.extern.slf4j.Slf4j;
+import org.junit.jupiter.api.Test;
+import top.fjy8018.designpattern.pattern.structural.proxy.IOrderService;
+import top.fjy8018.designpattern.pattern.structural.proxy.IOrderServiceImpl;
+import top.fjy8018.designpattern.pattern.structural.proxy.Order;
+
+/**
+ * @author F嘉阳
+ * @date 2020/3/3 15:54
+ */
+@Slf4j
+class OrderServiceDynamicProxyTest {
+
+    @Test
+    void invoke() {
+        Order order1 = new Order();
+        order1.setUserId(1);
+        Order order2 = new Order();
+        order2.setUserId(2);
+
+        // 动态代理直接代理接口
+        IOrderService proxy = (IOrderService) new OrderServiceDynamicProxy(new IOrderServiceImpl()).bind();
+        proxy.save(order1);
+        proxy.save(order2);
+    }
+}