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【Spring高级】ControllerAdvice

作者：笔触狂放9 | 2024-03-28 08:28:01

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【Spring高级】ControllerAdvice

目录


@ControllerAdvice是Spring框架提供的一个注解，用于对控制器提供一些增强功能，主要用于处理全局的异常、数据的绑定以及预处理请求参数等。

具体用法参考：@ControllerAdvice与@RestControllerAdvice

除了上面文章说到了用法，这里再补充下@InitBinder和@ResponseBodyAdvice

InitBinder

@InitBinder 的来源有两个：

  • @ControllerAdvice 中 @InitBinder 标注的方法，由 RequestMappingHandlerAdapter 在初始化时解析并记录
  • @Controller 中 @InitBinder 标注的方法，由 RequestMappingHandlerAdapter 会在控制器方法首次执行时解析并记录

所以，在RequestMappingHandlerAdapter执行控制器方法前，肯定要全部解析好@InitBinder，因为要对控制器方法进行增强。

看下RequestMappingHandlerAdapter源码有如下两个属性

private final Map<Class<?>, Set<Method>> initBinderCache = new ConcurrentHashMap<>(64);

private final Map<ControllerAdviceBean, Set<Method>> initBinderAdviceCache = new LinkedHashMap<>();

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  • initBinderCache：就是用来存储@Controller 中 @InitBinder 标注的方法
  • initBinderAdviceCache：用来存储@Controller 中 @InitBinder 标注的方法

当解析一个@InitBinder 时，就加到这两个缓存里，后面再遇到，直接从这两个缓存里找即可，不用每次解析了。

下面看一个实例，体会下两种@InitBinder用法的区别

首先沿用上一章的MyDateFormatter：

package com.cys.spring.chapter12;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.format.Formatter;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;


public class MyDateFormatter implements Formatter<Date> {
    private static final Logger log = LoggerFactory.getLogger(MyDateFormatter.class);
    private final String desc;

    public MyDateFormatter(String desc) {
        this.desc = desc;
    }

    @Override
    public String print(Date date, Locale locale) {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy|MM|dd");
        return sdf.format(date);
    }

    @Override
    public Date parse(String text, Locale locale) throws ParseException {
        log.debug(">>>>>> 进入了: {}", desc);
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy|MM|dd");
        return sdf.parse(text);
    }

}

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创建一个WebConfig

package com.cys.spring.chapter12;

import com.cys.spring.chapter12.MyDateFormatter;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.InitBinder;

@Configuration
public class WebConfig {

    @ControllerAdvice
    static class MyControllerAdvice {
        @InitBinder
        public void binder3(WebDataBinder webDataBinder) {
            webDataBinder.addCustomFormatter(new MyDateFormatter("binder3 转换器"));
        }
    }

    @Controller
    static class Controller1 {
        @InitBinder
        public void binder1(WebDataBinder webDataBinder) {
            webDataBinder.addCustomFormatter(new MyDateFormatter("binder1 转换器"));
        }

        public void foo() {

        }
    }

    @Controller
    static class Controller2 {
        @InitBinder
        public void binder21(WebDataBinder webDataBinder) {
            webDataBinder.addCustomFormatter(new MyDateFormatter("binder21 转换器"));
        }

        @InitBinder
        public void binder22(WebDataBinder webDataBinder) {
            webDataBinder.addCustomFormatter(new MyDateFormatter("binder22 转换器"));
        }

        public void bar() {

        }
    }

}

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测试类：

package com.cys.spring.chapter12;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.web.method.ControllerAdviceBean;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;


public class TestControllerAdvice {

    private static final Logger log = LoggerFactory.getLogger(TestControllerAdvice.class);

    public static void main(String[] args) throws Exception {

        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(WebConfig.class);

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

        log.debug("1. 刚开始...");
        showBindMethods(handlerAdapter);

        Method getDataBinderFactory = RequestMappingHandlerAdapter.class.getDeclaredMethod("getDataBinderFactory", HandlerMethod.class);
        getDataBinderFactory.setAccessible(true);

        log.debug("2. 模拟调用 Controller1 的 foo 方法时 ...");
        getDataBinderFactory.invoke(handlerAdapter, new HandlerMethod(new WebConfig.Controller1(), WebConfig.Controller1.class.getMethod("foo")));
        showBindMethods(handlerAdapter);

        log.debug("3. 模拟调用 Controller2 的 bar 方法时 ...");
        getDataBinderFactory.invoke(handlerAdapter, new HandlerMethod(new WebConfig.Controller2(), WebConfig.Controller2.class.getMethod("bar")));
        showBindMethods(handlerAdapter);

        context.close();
    }

    @SuppressWarnings("all")
    private static void showBindMethods(RequestMappingHandlerAdapter handlerAdapter) throws NoSuchFieldException, IllegalAccessException {
        Field initBinderAdviceCache = RequestMappingHandlerAdapter.class.getDeclaredField("initBinderAdviceCache");
        initBinderAdviceCache.setAccessible(true);
        Map<ControllerAdviceBean, Set<Method>> globalMap = (Map<ControllerAdviceBean, Set<Method>>) initBinderAdviceCache.get(handlerAdapter);
        log.debug("全局的 @InitBinder 方法 {}",
                globalMap.values().stream()
                        .flatMap(ms -> ms.stream().map(m -> m.getName()))
                        .collect(Collectors.toList())
        );

        Field initBinderCache = RequestMappingHandlerAdapter.class.getDeclaredField("initBinderCache");
        initBinderCache.setAccessible(true);
        Map<Class<?>, Set<Method>> controllerMap = (Map<Class<?>, Set<Method>>) initBinderCache.get(handlerAdapter);
        log.debug("控制器的 @InitBinder 方法 {}",
                controllerMap.entrySet().stream()
                        .flatMap(e -> e.getValue().stream().map(v -> e.getKey().getSimpleName() + "." + v.getName()))
                        .collect(Collectors.toList())
        );
    }
}

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运行结果如下：

12:00:31.528 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 1. 刚开始...
12:00:31.531 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 全局的 @InitBinder 方法 [binder3]
12:00:31.533 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 控制器的 @InitBinder 方法 []
12:00:31.534 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 2. 模拟调用 Controller1 的 foo 方法时 ...
12:00:31.540 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 全局的 @InitBinder 方法 [binder3]
12:00:31.541 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 控制器的 @InitBinder 方法 [Controller1.binder1]
12:00:31.541 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 3. 模拟调用 Controller2 的 bar 方法时 ...
12:00:31.542 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 全局的 @InitBinder 方法 [binder3]
12:00:31.542 [main] DEBUG com.cys.spring.chapter12.TestControllerAdvice - 控制器的 @InitBinder 方法 [Controller2.binder21, Controller2.binder22, Controller1.binder1]


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ResponseBodyAdvice

ResponseBodyAdvice 是 Spring Framework 提供的一个接口，用于在控制器方法返回响应体之前，对响应体进行自定义处理。通过实现这个接口，你可以拦截并修改响应体的内容，或者添加额外的逻辑，比如加密、序列化、添加日志等。

ResponseBodyAdvice 接口定义了两个方法：

  1. boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType): 这个方法用于判断当前的 ResponseBodyAdvice 是否支持处理给定的返回类型和转换器类型。如果返回 true，则 beforeBodyWrite 方法将会被调用；如果返回 false，则不会调用。
  2. Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response): 这个方法在实际写入响应体之前被调用，你可以在这里对响应体 body 进行处理，并返回处理后的结果。

示例：

假如我们有一个统一的返回类型Result<T>，那么我们想在控制器返回值做检查，如果返回的不是Result类型，我们就注定包装一层。

Result：

package com.cys.spring.chapter12;


import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;

@JsonInclude(JsonInclude.Include.NON_NULL)
public class Result {
    private int code;
    private String msg;
    private Object data;

    public int getCode() {
        return code;
    }

    public void setCode(int code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }

    public Object getData() {
        return data;
    }

    public void setData(Object data) {
        this.data = data;
    }

    @JsonCreator
    private Result(@JsonProperty("code") int code, @JsonProperty("data") Object data) {
        this.code = code;
        this.data = data;
    }

    private Result(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    public static Result ok() {
        return new Result(200, null);
    }

    public static Result ok(Object data) {
        return new Result(200, data);
    }

    public static Result error(String msg) {
        return new Result(500, "服务器内部错误:" + msg);
    }
}

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创建一个控制器：

package com.cys.spring.chapter12;

import org.springframework.context.annotation.Configuration;
import org.springframework.core.MethodParameter;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.mvc.method.annotation.ResponseBodyAdvice;

@Configuration
public class WebConfig2 {

    @ControllerAdvice
    static class MyControllerAdvice implements ResponseBodyAdvice<Object> {
        // 满足条件才转换
        @Override
        public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
					  // 先写死返回true
            return true;
        }

        // 将 User 或其它类型统一为 Result 类型
        @Override
        public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
            System.out.println("开始返回值包装");
            if (body instanceof Result) {
                return body;
            }
            return Result.ok(body);
        }
    }


    @Controller
    public static class MyController {
        @ResponseBody
        public User user() {
            return new User("王五", 18);
        }
    }

    public static class User {
        private String name;
        private int age;

        public User(String name, int age) {
            this.name = name;
            this.age = age;
        }

        public String getName() {
            return name;
        }

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

        public int getAge() {
            return age;
        }

        public void setAge(int age) {
            this.age = age;
        }
    }
}

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测试类：

package com.cys.spring.chapter12;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.core.DefaultParameterNameDiscoverer;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.mock.web.MockHttpServletRequest;
import org.springframework.mock.web.MockHttpServletResponse;
import org.springframework.web.context.request.ServletWebRequest;
import org.springframework.web.method.ControllerAdviceBean;
import org.springframework.web.method.annotation.ExpressionValueMethodArgumentResolver;
import org.springframework.web.method.annotation.RequestHeaderMethodArgumentResolver;
import org.springframework.web.method.annotation.RequestParamMethodArgumentResolver;
import org.springframework.web.method.support.HandlerMethodArgumentResolverComposite;
import org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite;
import org.springframework.web.method.support.ModelAndViewContainer;
import org.springframework.web.servlet.mvc.method.annotation.*;

import java.nio.charset.StandardCharsets;
import java.util.Collections;
import java.util.List;
import java.util.stream.Collectors;

public class TestResponseBodyAdvice {

    // {"name":"王五","age":18}
    // {"code":xx, "msg":xx, data: {"name":"王五","age":18} }
    public static void main(String[] args) throws Exception {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(WebConfig2.class);

        ServletInvocableHandlerMethod handlerMethod = new ServletInvocableHandlerMethod(
                context.getBean(WebConfig2.MyController.class),
                WebConfig2.MyController.class.getMethod("user")
        );
        handlerMethod.setDataBinderFactory(new ServletRequestDataBinderFactory(Collections.emptyList(), null));
        handlerMethod.setParameterNameDiscoverer(new DefaultParameterNameDiscoverer());
        handlerMethod.setHandlerMethodArgumentResolvers(getArgumentResolvers(context));
        handlerMethod.setHandlerMethodReturnValueHandlers(getReturnValueHandlers(context));

        MockHttpServletRequest request = new MockHttpServletRequest();
        MockHttpServletResponse response = new MockHttpServletResponse();
        ModelAndViewContainer container = new ModelAndViewContainer();
        handlerMethod.invokeAndHandle(new ServletWebRequest(request, response), container);

        System.out.println(new String(response.getContentAsByteArray(), StandardCharsets.UTF_8));

    }

    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(Collections.singletonList(new MappingJackson2HttpMessageConverter())),
                new ServletModelAttributeMethodProcessor(true),
                new RequestParamMethodArgumentResolver(context.getDefaultListableBeanFactory(), true)
        );
        return composite;
    }

    public static HandlerMethodReturnValueHandlerComposite getReturnValueHandlers(AnnotationConfigApplicationContext context) {
        // 添加 advice
        List<ControllerAdviceBean> annotatedBeans = ControllerAdviceBean.findAnnotatedBeans(context);
        List<Object> collect = annotatedBeans.stream().filter(b -> ResponseBodyAdvice.class.isAssignableFrom(b.getBeanType()))
                .collect(Collectors.toList());

        HandlerMethodReturnValueHandlerComposite composite = new HandlerMethodReturnValueHandlerComposite();
        composite.addHandler(new ModelAndViewMethodReturnValueHandler());
        composite.addHandler(new ViewNameMethodReturnValueHandler());
        composite.addHandler(new ServletModelAttributeMethodProcessor(false));
        composite.addHandler(new HttpEntityMethodProcessor(Collections.singletonList((new MappingJackson2HttpMessageConverter()))));
        composite.addHandler(new HttpHeadersReturnValueHandler());
        composite.addHandler(new RequestResponseBodyMethodProcessor(Collections.singletonList((new MappingJackson2HttpMessageConverter())), collect));
        composite.addHandler(new ServletModelAttributeMethodProcessor(true));
        return composite;
    }
}

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运行结果如下：

开始返回值包装
{"code":200,"data":{"name":"王五","age":18}}

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可以看到成功包装了一层，结果成为Result。

下面优化一下，让他只有加了@ResponseBody，才去包装，修改判断方法。

修改MyControllerAdvice如下：

@ControllerAdvice
    static class MyControllerAdvice implements ResponseBodyAdvice<Object> {
        // 满足条件才转换
        @Override
        public boolean supports(MethodParameter returnType, Class<? extends HttpMessageConverter<?>> converterType) {
            // ResponseBody注解加载方法上或类上，或者有RestController注解，都返回true
            // 使用 AnnotationUtil工具类
            if (returnType.getMethodAnnotation(ResponseBody.class) != null ||
                    AnnotationUtils.findAnnotation(returnType.getContainingClass(), ResponseBody.class) != null) {
//                returnType.getContainingClass().isAnnotationPresent(ResponseBody.class)) {
                return true;
            }
            return false;
        }

        // 将 User 或其它类型统一为 Result 类型
        @Override
        public Object beforeBodyWrite(Object body, MethodParameter returnType, MediaType selectedContentType, Class<? extends HttpMessageConverter<?>> selectedConverterType, ServerHttpRequest request, ServerHttpResponse response) {
            System.out.println("开始返回值包装");
            if (body instanceof Result) {
                return body;
            }
            return Result.ok(body);
        }
    }

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