第二十六讲-ControlerAdvice之@ModelAttribute

第二十六讲-ControlerAdvice之@ModelAttribute

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我们首先来了解一下@ModelAttribute注解的用法：

• 第一种是加在方法参数上
• 第二种是加在方法上

这两种我们在上一讲已经讲过。我们来看一下上讲的代码:

@Configuration
public class WebConfig {

    @ControllerAdvice
    static class MyControllerAdvice {
        @ModelAttribute("a")
        public String aa() {
            return "aa";
        }
    }

    @Controller
    static class Controller1 {
        @ModelAttribute("b")
        public String aa() {
            return "bb";
        }

        @ResponseStatus(HttpStatus.OK)
        public ModelAndView foo(@ModelAttribute("u") User user) {
            System.out.println("foo");
            return null;
        }
    }

    static class User {
        private String name;

        public void setName(String name) {
            this.name = name;
        }

        public String getName() {

            return name;
        }

        @Override
        public String toString() {
            return "User{" +
                   "name='" + name + '\'' +
                   '}';
        }
    }
}

public class A26 {

    public static void main(String[] args) throws Exception {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(WebConfig.class);

        RequestMappingHandlerAdapter adapter = new RequestMappingHandlerAdapter();
        adapter.setApplicationContext(context);
        adapter.afterPropertiesSet();

        MockHttpServletRequest request = new MockHttpServletRequest();
        request.setParameter("name", "张三");
        /*
            现在可以通过 ServletInvocableHandlerMethod 把这些整合在一起, 并完成控制器方法的调用, 如下
         */
        ServletInvocableHandlerMethod handlerMethod = new ServletInvocableHandlerMethod(
                new WebConfig.Controller1(), WebConfig.Controller1.class.getMethod("foo", WebConfig.User.class));

        // 添加处理绑定工厂
        ServletRequestDataBinderFactory factory = new ServletRequestDataBinderFactory(null, null);
        // 为handlerMethod设置数据绑定工厂
        handlerMethod.setDataBinderFactory(factory);
        // 为handlerMethod设置参数名解析器
        handlerMethod.setParameterNameDiscoverer(new DefaultParameterNameDiscoverer());
        // 为handlerMethod设置方法参数名解析器组合器
        handlerMethod.setHandlerMethodArgumentResolvers(getArgumentResolvers(context));
        // 创建一个存储中间数据的容器ModelAndViewContainer
        ModelAndViewContainer container = new ModelAndViewContainer();

        // 获取模型工厂方法
        Method getModelFactory = RequestMappingHandlerAdapter.class.getDeclaredMethod("getModelFactory", HandlerMethod.class, WebDataBinderFactory.class);
        getModelFactory.setAccessible(true);
        // 调用模型工厂中的invoke()方法初始化模型方法
        ModelFactory modelFactory = (ModelFactory) getModelFactory.invoke(adapter, handlerMethod, factory);

        // 初始化模型数据
        modelFactory.initModel(new ServletWebRequest(request), container, handlerMethod);

        // 反射调用该控制器
        handlerMethod.invokeAndHandle(new ServletWebRequest(request), container);

        System.out.println(container.getModel());

        context.close();

        /*
            学到了什么
                a. 控制器方法是如何调用的
                b. 模型数据如何产生
                c. advice 之二, @ModelAttribute 补充模型数据
         */
    }

    // 方法参数名解析器组合器(包含常见的方法参数解析器)
    public static HandlerMethodArgumentResolverComposite getArgumentResolvers(AnnotationConfigApplicationContext context) {
        HandlerMethodArgumentResolverComposite composite = new HandlerMethodArgumentResolverComposite();
        composite.addResolvers(
                new RequestParamMethodArgumentResolver(context.getDefaultListableBeanFactory(), false),
                new PathVariableMethodArgumentResolver(),
                new RequestHeaderMethodArgumentResolver(context.getDefaultListableBeanFactory()),
                new ServletCookieValueMethodArgumentResolver(context.getDefaultListableBeanFactory()),
                new ExpressionValueMethodArgumentResolver(context.getDefaultListableBeanFactory()),
                new ServletRequestMethodArgumentResolver(),
                new ServletModelAttributeMethodProcessor(false),
                new RequestResponseBodyMethodProcessor(List.of(new MappingJackson2HttpMessageConverter())),
                new ServletModelAttributeMethodProcessor(true),
                new RequestParamMethodArgumentResolver(context.getDefaultListableBeanFactory(), true)
        );
        return composite;
    }
}