利用反射简化代码

pom.xml

@@ -109,6 +109,10 @@
             <groupId>org.apache.httpcomponents</groupId>
             <artifactId>httpclient</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.apache.httpcomponents</groupId>
+            <artifactId>fluent-hc</artifactId>
+        </dependency>
 
         <dependency>
             <groupId>cglib</groupId>

src/main/java/com/example/demo_test/reflect/design/AbstractAPI.java

@@ -0,0 +1,5 @@
+package com.example.demo_test.reflect.design;
+
+public abstract class AbstractAPI {
+
+}

src/main/java/com/example/demo_test/reflect/design/BankAPI.java

@@ -0,0 +1,13 @@
+package com.example.demo_test.reflect.design;
+
+import java.lang.annotation.*;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.TYPE)
+@Documented
+@Inherited
+public @interface BankAPI {
+    String desc() default "";
+
+    String url() default "";
+}

src/main/java/com/example/demo_test/reflect/design/BankAPIField.java

@@ -0,0 +1,15 @@
+package com.example.demo_test.reflect.design;
+
+import java.lang.annotation.*;
+
+@Retention(RetentionPolicy.RUNTIME)
+@Target(ElementType.FIELD)
+@Documented
+@Inherited
+public @interface BankAPIField {
+    int order() default -1;
+
+    int length() default -1;
+
+    String type() default "";
+}

src/main/java/com/example/demo_test/reflect/design/BetterBankService.java

@@ -0,0 +1,84 @@
+package com.example.demo_test.reflect.design;
+
+import lombok.extern.slf4j.Slf4j;
+import org.apache.http.client.fluent.Request;
+import org.apache.commons.codec.digest.DigestUtils;
+import org.apache.http.entity.ContentType;
+
+import java.io.IOException;
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import java.util.Arrays;
+import java.util.Comparator;
+
+
+@Slf4j
+public class BetterBankService {
+
+    public static String createUser(String name, String identity, String mobile, int age) throws IOException {
+        CreateUserAPI createUserAPI = new CreateUserAPI();
+        createUserAPI.setName(name);
+        createUserAPI.setIdentity(identity);
+        createUserAPI.setAge(age);
+        createUserAPI.setMobile(mobile);
+        return remoteCall(createUserAPI);
+    }
+
+    public static String pay(long userId, BigDecimal amount) throws IOException {
+        PayAPI payAPI = new PayAPI();
+        payAPI.setUserId(userId);
+        payAPI.setAmount(amount);
+        return remoteCall(payAPI);
+    }
+
+    private static String remoteCall(AbstractAPI api) throws IOException {
+        //从BankAPI注解获取请求地址
+        BankAPI bankAPI = api.getClass().getAnnotation(BankAPI.class);
+        bankAPI.url();
+        StringBuilder stringBuilder = new StringBuilder();
+        Arrays.stream(api.getClass().getDeclaredFields()) //获得所有字段
+                .filter(field -> field.isAnnotationPresent(BankAPIField.class)) //查找标记了注解的字段
+                .sorted(Comparator.comparingInt(a -> a.getAnnotation(BankAPIField.class).order())) //根据注解中的order对字段排序
+                .peek(field -> field.setAccessible(true)) //设置可以访问私有字段
+                .forEach(field -> {
+                    //获得注解
+                    BankAPIField bankAPIField = field.getAnnotation(BankAPIField.class);
+                    Object value = "";
+                    try {
+                        //反射获取字段值
+                        value = field.get(api);
+                    } catch (IllegalAccessException e) {
+                        e.printStackTrace();
+                    }
+                    //根据字段类型以正确的填充方式格式化字符串
+                    switch (bankAPIField.type()) {
+                        case "S": {
+                            stringBuilder.append(String.format("%-" + bankAPIField.length() + "s", value.toString()).replace(' ', '_'));
+                            break;
+                        }
+                        case "N": {
+                            stringBuilder.append(String.format("%" + bankAPIField.length() + "s", value.toString()).replace(' ', '0'));
+                            break;
+                        }
+                        case "M": {
+                            if (!(value instanceof BigDecimal))
+                                throw new RuntimeException(String.format("{} 的 {} 必须是BigDecimal", api, field));
+                            stringBuilder.append(String.format("%0" + bankAPIField.length() + "d", ((BigDecimal) value).setScale(2, RoundingMode.DOWN).multiply(new BigDecimal("100")).longValue()));
+                            break;
+                        }
+                        default:
+                            break;
+                    }
+                });
+        //签名逻辑
+        stringBuilder.append(DigestUtils.md2Hex(stringBuilder.toString()));
+        String param = stringBuilder.toString();
+        long begin = System.currentTimeMillis();
+        //发请求
+        String result = Request.Post("http://localhost:45678/reflection" + bankAPI.url())
+                .bodyString(param, ContentType.APPLICATION_JSON)
+                .execute().returnContent().asString();
+        log.info("调用银行API {} url:{} 参数:{} 耗时:{}ms", bankAPI.desc(), bankAPI.url(), param, System.currentTimeMillis() - begin);
+        return result;
+    }
+}

src/main/java/com/example/demo_test/reflect/design/CreateUserAPI.java

@@ -0,0 +1,16 @@
+package com.example.demo_test.reflect.design;
+
+import lombok.Data;
+
+@BankAPI(url = "/bank/createUser", desc = "创建用户接口")
+@Data
+public class CreateUserAPI extends AbstractAPI {
+    @BankAPIField(order = 1, type = "S", length = 10)
+    private String name;
+    @BankAPIField(order = 2, type = "S", length = 18)
+    private String identity;
+    @BankAPIField(order = 4, type = "S", length = 11)
+    private String mobile;
+    @BankAPIField(order = 3, type = "N", length = 5)
+    private int age;
+}

src/main/java/com/example/demo_test/reflect/design/PayAPI.java

@@ -0,0 +1,14 @@
+package com.example.demo_test.reflect.design;
+
+import lombok.Data;
+
+import java.math.BigDecimal;
+
+@BankAPI(url = "/bank/pay", desc = "支付接口")
+@Data
+public class PayAPI extends AbstractAPI {
+    @BankAPIField(order = 1, type = "N", length = 20)
+    private long userId;
+    @BankAPIField(order = 2, type = "M", length = 10)
+    private BigDecimal amount;
+}