一. 前期准备

1.1 标记邮箱种类的接口

import java.lang.annotation.*;

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD})
public @interface MailCategoryAnnotation {

    String mailCode();
}

1.2 邮箱类型区分类

考虑到之后可能会有其他类型的区分，因此使用了内部class

public final class CategoryKbn {

    // 邮件种类
    public final class MailCategory {
        public final static String Mail_163 = "1";
        public final static String Mail_QQ = "2";
        public final static String Mail_G = "3";
        public final static String Mail_OutLook = "4";
    }
	// 其他种类。。。
}

1.3 入参Form实体类

import lombok.Data;

@Data
public class Test27Form {
	
	// 用于标记邮箱的种类
    private String category;
}

二. 邮件发送的业务聚合类

自定义的注解作用在Method上，用来标记邮件发送方法的类型

import org.springframework.stereotype.Component;

import java.util.Map;

@Component
public class SendMailService {
	
    @MailCategoryAnnotation(mailCode = CategoryKbn.MailCategory.Mail_QQ)
    public void sendQQMail(Map<String, String> mailInfoMap) {
        System.out.println("QQ邮箱发送邮件。。。");
        System.out.println(mailInfoMap);
    }

    @MailCategoryAnnotation(mailCode = CategoryKbn.MailCategory.Mail_163)
    public void send163Mail(Map<String, String> mailInfoMap) {
        System.out.println("163邮箱发送邮件。。。");
        System.out.println(mailInfoMap);
    }

    @MailCategoryAnnotation(mailCode = CategoryKbn.MailCategory.Mail_G)
    public void sendGMail(Map<String, String> mailInfoMap) {
        System.out.println("GMail邮箱发送邮件。。。");
        System.out.println(mailInfoMap);
    }

    @MailCategoryAnnotation(mailCode = CategoryKbn.MailCategory.Mail_OutLook)
    public void sendOutLookMail(Map<String, String> mailInfoMap) {
        System.out.println("OutLook邮箱发送邮件。。。");
        System.out.println(mailInfoMap);
    }
}

三. 定义函数式接口，创建邮件发送的Map

import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

@Service
public class Test27Service implements InitializingBean {

    @Autowired
    private SendMailService mailService;
	
	/*
		邮件种类code和发送邮件方法的映射Map
	*/
    private final Map<String, MailFunction<Map<String, String>>> strategySendMailMap = new HashMap<>();


    // 标记此接口为函数式编程接口
    @FunctionalInterface
    interface MailFunction<T> {
    	// 不知道参数会是什么类型,就使用了泛型
        void sendMail(T mailInfo) throws Exception;
    }
    
    @Override
    public void afterPropertiesSet() throws Exception {

        for (Method mailSendMethod : Arrays.asList(mailService.getClass().getMethods())) {			
        	// 如果该方法上没有被标记MailCategoryAnnotation自定义注解就跳过
            if (!mailSendMethod.isAnnotationPresent(MailCategoryAnnotation.class)) {
                continue;
            }
			
			// 获取Method上被标记的MailCategoryAnnotation注解上的mailCode
            String mailCode = mailSendMethod.getAnnotation(MailCategoryAnnotation.class).mailCode();
            
            // 将mailcode和发送邮件的方法添加到Map中
            strategySendMailMap.put(mailCode, (T) -> mailSendMethod.invoke(mailService, T));
        }
    }


    public void execute(String category) throws Exception {
    	
    	// 发送邮件时所需要的参数
    	Map<String, String> mailInfoMap = new HashMap<>() {
            {
                put("id", "110120");
                put("name", "jiafeitian");
            }
        };
        
        // 根据category获取邮件的发送方法,并执行
        MailFunction<Map<String, String>> sendMailFunction = strategySendMailMap.get(category);
        sendMailFunction.sendMail(mailInfoMap);
    }
}

四. 效果

⏹前台

const jsonData = {
    category: '2'
};

$.ajax({
    url: "/test27/test1",
    type: 'POST',
    data: JSON.stringify(jsonData),
    contentType: 'application/json;charset=utf-8',
    success: function (data, status, xhr) {
        console.log(data);
    }
});

⏹后台

import org.springframework.web.bind.annotation.*;
import org.springframework.http.ResponseEntity;

@PostMapping("/test1")
public ResponseEntity<Void> test1(@RequestBody Test27Form form) throws Exception {

    service.execute(form.getCategory());
    return ResponseEntity.noContent().build();
}