springboot RequestBodyAdvice说明

系统管理员 2022-09-03 14:17 139阅读 0赞

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## springboot RequestBodyAdvice说明 ##

**应用：处理控制器请求参数@RequestBody**

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**相关类与接口**

**RequestBodyAdvice**

public interface RequestBodyAdvice {
        boolean supports(MethodParameter var1, Type var2, Class<? extends HttpMessageConverter<?>> var3);
                //var1：方法参数，@RequestBody标注的参数
                //var2：方法参数类型
                //var3：使用的参数转换器（HttpMessageConverter）
                //beforeBodyRead、afterBodyRead在执行之前都会调用supports
                //返回true则执行，返回false不执行
    
        HttpInputMessage beforeBodyRead(HttpInputMessage var1, MethodParameter var2, Type var3, Class<? extends HttpMessageConverter<?>> var4) throws IOException;
    
        Object afterBodyRead(Object var1, HttpInputMessage var2, MethodParameter var3, Type var4, Class<? extends HttpMessageConverter<?>> var5);
    
        @Nullable
        Object handleEmptyBody(@Nullable Object var1, HttpInputMessage var2, MethodParameter var3, Type var4, Class<? extends HttpMessageConverter<?>> var5);
                //请求体为空时调用
    }

**RequestBodyAdviceAdapter**

public abstract class RequestBodyAdviceAdapter implements RequestBodyAdvice {
        public RequestBodyAdviceAdapter() {
        }
    
        public HttpInputMessage beforeBodyRead(HttpInputMessage inputMessage, MethodParameter parameter, Type targetType, Class<? extends HttpMessageConverter<?>> converterType) throws IOException {
            return inputMessage;
        }
    
        public Object afterBodyRead(Object body, HttpInputMessage inputMessage, MethodParameter parameter, Type targetType, Class<? extends HttpMessageConverter<?>> converterType) {
            return body;
        }
    
        @Nullable
        public Object handleEmptyBody(@Nullable Object body, HttpInputMessage inputMessage, MethodParameter parameter, Type targetType, Class<? extends HttpMessageConverter<?>> converterType) {
            return body;
        }
    }

**HttpInputMessage**

public interface HttpInputMessage extends HttpMessage {
        InputStream getBody() throws IOException;
    }

**MethodParameter**

public class MethodParameter {
        private static final Annotation[] EMPTY_ANNOTATION_ARRAY = new Annotation[0];
        private final Executable executable;
        private final int parameterIndex;
        @Nullable
        private volatile Parameter parameter;
        private int nestingLevel;
        @Nullable
        Map<Integer, Integer> typeIndexesPerLevel;
        @Nullable
        private volatile Class<?> containingClass;
        @Nullable
        private volatile Class<?> parameterType;        //参数类型
        @Nullable
        private volatile Type genericParameterType;
        @Nullable
        private volatile Annotation[] parameterAnnotations;
        @Nullable
        private volatile ParameterNameDiscoverer parameterNameDiscoverer;
        @Nullable
        private volatile String parameterName;
        @Nullable
        private volatile MethodParameter nestedMethodParameter;

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**示例**

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**pojo 层**

**Person**

@Data
    public class Person {
    
        private String name;
        private Integer age;
    }

**Student**

@Data
    public class Student {
    
        private String name;
        private Integer age;
    }

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**advice 层**

**CustomRequestBodyAdvice**

@ControllerAdvice(basePackages = {"com.example.demo.controller"})
    public class CustomRequestBodyAdvice extends RequestBodyAdviceAdapter {
    
        @Override
        public boolean supports(MethodParameter methodParameter, Type type, Class<? extends HttpMessageConverter<?>> aClass) {
            System.out.println("supports methodParameter "+methodParameter.getParameter().getName());
            System.out.println("supports methodParameter "+methodParameter.getParameter().getType().getName());
            System.out.println("supports type "+type.getTypeName());
    
            if (methodParameter.getParameter().getType().getSimpleName().equals("Person")){
                return true;
            }
    
            return false;
        }
    
        @Override
        public HttpInputMessage beforeBodyRead(HttpInputMessage inputMessage, MethodParameter parameter, Type targetType, Class<? extends HttpMessageConverter<?>> converterType) throws IOException {
            System.out.println("\nbeforeBodyRead ");
    
            byte[] bytes=new byte[inputMessage.getBody().available()];
            inputMessage.getBody().read(bytes);
    
            String s=new String(bytes);
            System.out.println(s+"\n");
    
            return new HttpInputMessage() {
                @Override
                public InputStream getBody() throws IOException {
                    return new ByteArrayInputStream(s.getBytes());
                }
    
                @Override
                public HttpHeaders getHeaders() {
                    return inputMessage.getHeaders();
                }
            };
        }
    
        @Override
        public Object afterBodyRead(Object body, HttpInputMessage inputMessage, MethodParameter parameter, Type targetType, Class<? extends HttpMessageConverter<?>> converterType) {
            System.out.println("afterBodyRead "+body);
    
            return super.afterBodyRead(body, inputMessage, parameter, targetType, converterType);
        }
    
        @Override
        public Object handleEmptyBody(Object body, HttpInputMessage inputMessage, MethodParameter parameter, Type targetType, Class<? extends HttpMessageConverter<?>> converterType) {
            System.out.println("handleEmptyBody "+body);
    
            Person person=new Person();
            person.setName("火影忍者");
            person.setAge(20);
    
            return person;
        }
    }

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**controller 层**

**HelloController**

@RestController
    public class HelloController {
    
        @RequestMapping("/hello")
        public Person hello(String name, Integer age){
            Person person=new Person();
            person.setName(name);
            person.setAge(age);
            System.out.println(person);
    
            return person;
        }
    
        @RequestMapping("/hello2")
        public Person hello2(@RequestBody Person person){
            System.out.println(person);
    
            return person;
        }
    
        @RequestMapping("/hello3")
        public Student hello3(@RequestBody Student student){
            System.out.println(student);
    
            return student;
        }
    }

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**测试输出**

**localhost:8080/hello?name=瓜田李下&age=20，控制台输出：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkzMTYyNQ_size_16_color_FFFFFF_t_70][]

2021-08-08 18:37:43.099  INFO 17136 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
    2021-08-08 18:37:43.099  INFO 17136 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet        : Completed initialization in 0 ms
    Person(name=瓜田李下, age=20)

**说明：****方法上没有注解@RequestBody，不会调用CustomRequestBodyAdvice**

**localhost:8080/hello2，控制台输出：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkzMTYyNQ_size_16_color_FFFFFF_t_70 1][]

supports methodParameter person
    supports methodParameter com.example.demo.pojo.Person
    supports type com.example.demo.pojo.Person
    
    beforeBodyRead 
    {
        "name":"瓜田李下",
        "age": 20
    }
    #beforeBodyRead执行之前调用supports，判断是否执行beforeBodyRead方法
    
    
    supports methodParameter person
    supports methodParameter com.example.demo.pojo.Person
    supports type com.example.demo.pojo.Person
    afterBodyRead Person(name=瓜田李下, age=20)
    #afterBodyRead执行之前调用supports，判断是否执行afterBodyRead方法
    
    Person(name=瓜田李下, age=20)

**localhost:8080/hello3，控制台输出：**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkzMTYyNQ_size_16_color_FFFFFF_t_70 2][]

supports methodParameter student
    supports methodParameter com.example.demo.pojo.Student
    supports type com.example.demo.pojo.Student
    supports methodParameter student
    supports methodParameter com.example.demo.pojo.Student
    supports type com.example.demo.pojo.Student
    Student(name=海贼王, age=20)

**说明：supports 返回的均为false，beforeBodyRead、afterBodyRead不会调用**

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzkzMTYyNQ_size_16_color_FFFFFF_t_70 1]: /images/20220829/40229a40c24147bdbb0dd3dc8f7c8a0e.png
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