Spring中如何自定义一个类似Controller注解呢？

今天接到一个特殊的需求，我们自定义一个类似@Controller注解，那么如何实现这一需求呢?下文笔者将一一道来，如下所示

自定义类似@Controller注解的实现思路

1.定义新注解
2.创建注解处理器
3.注册自定义handler
4.使用自定义注解

例:

1.定义自定义注解

定义`@CustomController`注解
 
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.TYPE) // 仅适用于类
@Retention(RetentionPolicy.Runtime) // 保留到运行时
public @interface CustomController {
    String value() default ""; // 可选属性
}

2.创建注解处理器

创建 `CustomRequestMappingHandlerMapping`
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;

import javax.annotation.PostConstruct;
import java.util.Map;

@Configuration
public class CustomRequestMappingHandlerMapping extends RequestMappingHandlerMapping {

    @Autowired
    private Map<String, Object> beanMap;

    @PostConstruct
    protected void initHandlerMethods() {
        super.initHandlerMethods();
        for (Map.Entry<String, Object> entry : beanMap.entrySet()) {
            Object bean = entry.getValue();
            if (bean.getClass().isAnnotationPresent(CustomController.class)) {
                detectHandlerMethods(bean);
            }
        }
    }
}

3.注册自定义`HandlerMapping`

 
确保自定义`HandlerMapping`
 被Spring容器识别和注册 

配置类
 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class WebConfig {

    @Bean
    public CustomRequestMappingHandlerMapping customRequestMappingHandlerMapping() {
        return new CustomRequestMappingHandlerMapping();
    }
}

4.使用自定义注解

使用`@CustomController`注解 

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@CustomController
public class MyCustomController {

    @GetMapping("/custom")
    @ResponseBody
    public String customEndpoint() {
        return "Hello from Custom Controller!";
    }
}

完整示例

自定义注解 `CustomController`
 
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.TYPE) // 仅适用于类
@Retention(RetentionPolicy.RUNTIME) // 保留到运行时
public @interface CustomController {
    String value() default ""; // 可选属性
}
 
自定义`HandlerMapping`

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;

import javax.annotation.PostConstruct;
import java.util.Map;

@Configuration
public class CustomRequestMappingHandlerMapping extends RequestMappingHandlerMapping {

    @Autowired
    private Map<String, Object> beanMap;

    @PostConstruct
    protected void initHandlerMethods() {
        super.initHandlerMethods();
        for (Map.Entry<String, Object> entry : beanMap.entrySet()) {
            Object bean = entry.getValue();
            if (bean.getClass().isAnnotationPresent(CustomController.class)) {
                detectHandlerMethods(bean);
            }
        }
    }
}

配置类

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class WebConfig {

    @Bean
    public CustomRequestMappingHandlerMapping customRequestMappingHandlerMapping() {
        return new CustomRequestMappingHandlerMapping();
    }
}
  
使用自定义注解的控制器

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@CustomController
public class MyCustomController {

    @GetMapping("/custom")
    @ResponseBody
    public String customEndpoint() {
        return "Hello from Custom Controller!";
    }
}

完整示例运行及测试

pring Boot 应用程序
 
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class CustomControllerApplication {

    public static void main(String[] args) {
        SpringApplication.run(CustomControllerApplication.class, args);
    }
}
    
启动应用程序后
访问 `http://localhost:8080/custom`
 浏览器将会返回 `Hello from Custom Controller!`