动态注册controller

• 动态注册controller
  • 动态注册controller
    • 步骤概述
    • 代码示例

动态注册controller

步骤概述

• 第一步：利用org.springframework.beans.factory.support.DefaultListableBeanFactory#registerBeanDefinition将类注册为spring bean
• 第二步：利用org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#detectHandlerMethods(java.lang.Object)，将spring-bean解析为controller

代码示例

• 工具类SpringRegister

  import lombok.extern.slf4j.Slf4j;
  import org.springframework.beans.factory.config.BeanDefinition;
  import org.springframework.beans.factory.support.BeanDefinitionBuilder;
  import org.springframework.beans.factory.support.DefaultListableBeanFactory;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.ConfigurableApplicationContext;
  import org.springframework.util.StringUtils;
  import org.springframework.web.servlet.handler.AbstractHandlerMethodMapping;
  import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
  
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  
  /**
   * spring 注册器
   *
   * @author <font size = "20" color = "#3CAA3C"><a href="https://gitee.com/JustryDeng">JustryDeng</a></font> <img src="https://gitee.com/JustryDeng/shared-files/raw/master/JustryDeng/avatar.jpg" />
   * @since 2022/6/28 13:31
   */
  @Slf4j
  public final class SpringRegister {
      
      private SpringRegister() {
          throw new UnsupportedOperationException("non-support create SpringRegister instance.");
      }
      
      /**
       * 注册spring bean
       *
       * @see SpringRegister#registerBean(ApplicationContext, Class, String, String)
       */
      public static String registerBean(ApplicationContext applicationContext, Class<?> clazz) {
          String beanName = StringUtils.uncapitalize(clazz.getSimpleName());
          beanName = StringUtils.uncapitalize(beanName);
          return registerBean(applicationContext, clazz, beanName, "singleton");
      }
      
      /**
       * 注册spring bean
       *
       * @see SpringRegister#registerBean(ApplicationContext, Class, String, String)
       */
      public static String registerBean(ApplicationContext applicationContext, Class<?> clazz, String beanName) {
          return registerBean(applicationContext, clazz, beanName, "singleton");
      }
      
      /**
       * 注册spring bean
       *
       * @param applicationContext
       *         spring上下文
       * @param clazz
       *         要注册的class
       * @param beanName
       *         bean name
       * @param scope
       *         作用域
       *
       * @return bean name
       */
      public static String registerBean(ApplicationContext applicationContext, Class<?> clazz, String beanName,
                                        String scope) {
          Object bean = null;
          try {
              bean = applicationContext.getBean(beanName);
          } catch (Exception e) {
              // ignore
          }
          
          BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(clazz);
          BeanDefinition beanDefinition = beanDefinitionBuilder.getRawBeanDefinition();
          // 设置当前bean的作用域
          beanDefinition.setScope(scope);
          // 将applicationContext转换为ConfigurableApplicationContext
          ConfigurableApplicationContext configurableApplicationContext =
                  (ConfigurableApplicationContext) applicationContext;
          // 获取bean工厂并转换为DefaultListableBeanFactory
          DefaultListableBeanFactory defaultListableBeanFactory =
                  (DefaultListableBeanFactory) configurableApplicationContext.getBeanFactory();
          if (bean != null) {
              log.warn("A bean with name '" + beanName + "' has already been defined. It is '" + bean + "'. We try to "
                      + "overriding it with bean '" + beanDefinition + "'.");
          }
          defaultListableBeanFactory.registerBeanDefinition(beanName, beanDefinition);
          log.debug("register bean '" + beanName + "' success.");
          return beanName;
      }
      
      /**
       * 将指定bean解析controller bean
       * <br>
       * 核心是利用{@link AbstractHandlerMethodMapping#detectHandlerMethods(java.lang.Object)}，将spring-bean解析为controller
       *
       * @param applicationContext
       *         spring上下文
       * @param beanName
       *         要解析的spring bean
       */
      public static void registerController(ApplicationContext applicationContext, String beanName) {
          // step1. 检查beanName存在
          Object bean = null;
          try {
              bean = applicationContext.getBean(beanName);
          } catch (Exception e) {
              // ignore
          }
          if (bean == null) {
              throw new RuntimeException("non-exist spring bean whose name  is [" + beanName + "]. Please register it "
                      + "first.");
          }
          
          // step2. 将beanName解析为controller
          try {
              RequestMappingHandlerMapping requestMappingHandlerMapping =
                      applicationContext.getBean(RequestMappingHandlerMapping.class);
              Method method =
                      requestMappingHandlerMapping.getClass().getSuperclass().getSuperclass().getDeclaredMethod(
                              "detectHandlerMethods", Object.class);
              boolean accessible = method.isAccessible();
              method.setAccessible(true);
              method.invoke(requestMappingHandlerMapping, beanName);
              method.setAccessible(accessible);
          } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) {
              throw new RuntimeException("registerController occur exception.", e);
          }
          log.debug("register controller-bean '" + beanName + "' success.");
      }
  }

• 要动态注册的controller

  import org.springframework.http.MediaType;
  import org.springframework.http.ResponseEntity;
  import org.springframework.web.bind.annotation.GetMapping;
  import org.springframework.web.bind.annotation.RequestParam;
  
  import java.util.HashMap;
  import java.util.Map;
  
  public class NormalController {
      
      
      @GetMapping("/fa")
      public ResponseEntity<Map<String, Object>> methodAbc(@RequestParam("name") String name,
                                                           @RequestParam("age") Integer age) {
          Map<String, Object> data = new HashMap<>(4);
          data.put("name", name);
          data.put("age", age);
          return ResponseEntity.ok().contentType(MediaType.APPLICATION_JSON).body(data);
      }
      
  }

• 进行注册

  import com.example.registercontroller.register.NormalController;
  import com.example.registercontroller.register.SpringRegister;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.boot.ApplicationArguments;
  import org.springframework.boot.ApplicationRunner;
  import org.springframework.boot.SpringApplication;
  import org.springframework.boot.autoconfigure.SpringBootApplication;
  import org.springframework.context.ApplicationContext;
  
  @SpringBootApplication
  public class RegisterControllerApplication implements ApplicationRunner {
      
      @Autowired
      ApplicationContext applicationContext;
      
      public static void main(String[] args) {
          SpringApplication.run(RegisterControllerApplication.class, args);
      }
      
      @Override
      public void run(ApplicationArguments args) throws Exception {
          // 第一步：利用`org.springframework.beans.factory.support.DefaultListableBeanFactory#registerBeanDefinition`将类注册为spring bean
          String beanName = SpringRegister.registerBean(applicationContext, NormalController.class);
          // 第二步：利用`org.springframework.web.servlet.handler.AbstractHandlerMethodMapping#detectHandlerMethods(java.lang.Object)`，将spring-bean解析为controller
          SpringRegister.registerController(applicationContext, beanName);
      }
  }

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