HandlerMethodArgumentResolver

    1. 第一个方法用来判断是否需要进行参数解析
    2. 第二个方法返回值就是解析的参数值
    1. 方法分析
    2. 自定义解析器需要实现HandlerMethodArgumentResolver接口，HandlerMethodArgumentResolver接口包含两个接口：
    3. package org.springframework.web.method.support;
    5. import org.springframework.core.MethodParameter;
    6. import org.springframework.web.bind.WebDataBinder;
    7. import org.springframework.web.bind.support.WebDataBinderFactory;
    8. import org.springframework.web.context.request.NativeWebRequest;
    10. /**
    12. ●  Strategy interface for resolving method parameters into argument values in 
    13. ●  the context of a given request. 
    14. ● 
    15. ●  @author  Arjen Poutsma  
    16. ●  @since  3.1  
    17. ●  @see  HandlerMethodReturnValueHandler 
    18. */
    19. public interface HandlerMethodArgumentResolver {
    20. boolean supportsParameter(MethodParameter parameter);
    21. Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,
    22. NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception; 
    24. }
    25. 2.1 接口说明：
    27. supportsParameter：用于判定是否需要处理该参数分解，返回true为需要，并会去调用下面的方法resolveArgument。
    28. resolveArgument：真正用于处理参数分解的方法，返回的Object就是controller方法上的形参对象。
    1. 使用方法
    2. 3.1 自定义注解
    3. import java.lang.annotation.ElementType;
    4. import java.lang.annotation.Retention;
    5. import java.lang.annotation.RetentionPolicy;
    6. import java.lang.annotation.Target;
    8. /**
    10. ● 登录用户信息
    11. */
    12. @Target(ElementType.PARAMETER)
    13. @Retention(RetentionPolicy.RUNTIME)
    14. public @interface  LoginUser { 
    16. }
    1. 3.2 自定义参数解析器，实现HandlerMethodArgumentResolver接口
    3. package io.renren.modules.app.resolver;
    5. import io.renren.modules.app.annotation.LoginUser;
    6. import io.renren.modules.app.entity.UserEntity;
    7. import io.renren.modules.app.interceptor.AuthorizationInterceptor;
    8. import io.renren.modules.app.service.UserService;
    9. import org.springframework.beans.factory.annotation.Autowired;
    10. import org.springframework.core.MethodParameter;
    11. import org.springframework.stereotype.Component;
    12. import org.springframework.web.bind.support.WebDataBinderFactory;
    13. import org.springframework.web.context.request.NativeWebRequest;
    14. import org.springframework.web.context.request.RequestAttributes;
    15. import org.springframework.web.method.support.HandlerMethodArgumentResolver;
    16. import org.springframework.web.method.support.ModelAndViewContainer;
    18. /**
    20. ●  有@LoginUser注解的方法参数，注入当前登录用户
    21. */
    22. @Component  
    23. public class LoginUserHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver {
    24. @Autowired  
    25. private UserService userService;
    26. @Override  
    27. public boolean supportsParameter(MethodParameter parameter) {
    28. return parameter.getParameterType().isAssignableFrom(UserEntity.class) && parameter.hasParameterAnnotation(LoginUser.class);
    29. }
    30. @Override  
    31. public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer container,
    32. NativeWebRequest request, WebDataBinderFactory factory) throws Exception {
    33. //获取用户ID
    34. Object object = request.getAttribute(AuthorizationInterceptor.USER_KEY, RequestAttributes.SCOPE_REQUEST);
    35. if(object == null){
    36. return null;
    37. }
    38. //获取用户信息
    39. UserEntity user = userService.selectById((Long)object);
    40. return user;
    41. }
    42. }
    1. 3.3 注册自定义参数解析器
    2. Springboot中使用方法： 
    4. import java.util.List;
    6. /**
    8. ●  MVC配置
    9. */
    10. @Configuration  
    11. public class WebMvcConfig extends WebMvcConfigurerAdapter {
    12. @Autowired  
    13. private AuthorizationInterceptor authorizationInterceptor;
    14. @Autowired  
    15. private LoginUserHandlerMethodArgumentResolver loginUserHandlerMethodArgumentResolver;
    16. @Override  
    17. public void addInterceptors(InterceptorRegistry registry) {
    18. registry.addInterceptor(authorizationInterceptor).addPathPatterns("/api/**");
    19. }
    20. @Override  
    21. public void addArgumentResolvers(List argumentResolvers) {
    22. argumentResolvers.add(loginUserHandlerMethodArgumentResolver);
    23. }
    24. } 
    26. 3.4 Controller使用自定义注解
    28. @GetMapping("info")
    29. public UserEntity userInfo(@LoginUser UserEntity user){
    30.     return user;
    31. }
    32. 。