3 形参注解_牛客博客

1、@PathVariable

@PathVariable：映射URL绑定的占位符。
适用REST。

  package com.xianhuii;

  import org.springframework.stereotype.Controller;
  import org.springframework.web.bind.annotation.PathVariable;
  import org.springframework.web.bind.annotation.RequestMapping;
  import org.springframework.web.bind.annotation.RequestMethod;

  @Controller
  @RequestMapping("/springmvc")
  public class RequestMappingTest01 {
      private static final String SUCCESS = "success";

      @RequestMapping("/testPathVariable/{id}")
      public String testPathVariable(@PathVariable("id") Integer id) {
          System.out.println(id);
          return SUCCESS;
      }

  }

2、REST

REST（Representational State Transfer）：（资源）表现层状态转化。
资源（Resources）：网络上的一个实体，每种资源对应一个特定的URI。
表现层（Representation）：把资源具体呈现出来的形式。
状态转化（State Transfer）：每发出一个请求，就代表了客户端和服务器的一次交互过程。HTTP协议是一种无状态的协议，所有的状态都保存在服务器端。因此，如果客户端想要操作服务器，就必须通过某种手段，让服务器端发生“转台转化”（State Transfer）。具体来说，就是HTTP协议里面，四个表示操作方式的动词：GET、POST、PUT、DELETE。它们分别敌营四种基本操作：GET用来获取资源，POST用来新建资源，PUT用来更新资源，DELETE用来删除资源。
```
/order/1 GET：获取id=1的order
/order/1 DELETE：删除id=1的order
/order/1 PUT：更新id=1的order
/order POST：新增order
```

3、HiddenHttpMethodFilter过滤器

HiddenHttpMethodFilter：将POST请求转为DELETE、PUT请求。

源码：

package org.springframework.web.filter;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Locale;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import org.springframework.http.HttpMethod;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

public class HiddenHttpMethodFilter extends OncePerRequestFilter {
    private static final List<String> ALLOWED_METHODS;
    public static final String DEFAULT_METHOD_PARAM = "_method";
    private String methodParam = "_method";

    public HiddenHttpMethodFilter() {
    }

    public void setMethodParam(String methodParam) {
        Assert.hasText(methodParam, "'methodParam' must not be empty");
        this.methodParam = methodParam;
    }

    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
        HttpServletRequest requestToUse = request;
        if ("POST".equals(request.getMethod()) && request.getAttribute("javax.servlet.error.exception") == null) {
            String paramValue = request.getParameter(this.methodParam);
            if (StringUtils.hasLength(paramValue)) {
                String method = paramValue.toUpperCase(Locale.ENGLISH);
                if (ALLOWED_METHODS.contains(method)) {
                    requestToUse = new HiddenHttpMethodFilter.HttpMethodRequestWrapper(request, method);
                }
            }
        }

        filterChain.doFilter((ServletRequest)requestToUse, response);
    }

    static {
        ALLOWED_METHODS = Collections.unmodifiableList(Arrays.asList(HttpMethod.PUT.name(), HttpMethod.DELETE.name(), HttpMethod.PATCH.name()));
    }

    private static class HttpMethodRequestWrapper extends HttpServletRequestWrapper {
        private final String method;

        public HttpMethodRequestWrapper(HttpServletRequest request, String method) {
            super(request);
            this.method = method;
        }

        public String getMethod() {
            return this.method;
        }
    }

}

配置（web.xml）：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">

    <!--配置HidenHttpMethodFilter：将POST请求转为DELETE、PUT请求-->
    <filter>
        <filter-name>hiddenHttpMethodFilter</filter-name>
        <filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>hiddenHttpMethodFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

</web-app>

前端：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>

  <head>
    <title>$Title$</title>
  </head>

  <body>
  <%--GET--%>
  <a href="/springmvc/testRest/1">testRest1</a><br>
  <%--POST--%>

  <form action="/springmvc/testRest" method="post">
    <input type="submit" value="testRest POST">
  </form>

  <%--DELETE--%>

  <form action="/springmvc/testRest/1" method="post">
    <input type="hidden" name="_method" value="DELETE">
    <input type="submit" value="testRest DELETE">
  </form>

  <%--PUT--%>

  <form action="/springmvc/testRest/1" method="post">
    <input type="hidden" name="_method" value="PUT">
    <input type="submit" value="testRest PUT">
  </form>

  </body>
</html>

Controller：

package com.xianhuii;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
@RequestMapping("/springmvc")
public class RequestMappingTest01 {
    private static final String SUCCESS = "success";

    @RequestMapping(value = "/testRest/{id}", method = RequestMethod.GET)
    public String testRestGet(@PathVariable("id") Integer id) {
        System.out.println("get" + id);
        return SUCCESS;
    }

    @RequestMapping(value = "/testRest/", method = RequestMethod.POST)
    public String testRestPost() {
        System.out.println("POST");
        return SUCCESS;
    }

    @RequestMapping(value = "/testRest/{id}", method = RequestMethod.DELETE)
        //@ResponseBody
    public String testRestDelete(@PathVariable("id") Integer id) {
        System.out.println("DELETE" + id);
        return SUCCESS;
    }

    @RequestMapping(value = "/testRest/{id}", method = RequestMethod.PUT)
        //@ResponseBody
    public String testRestPut(@PathVariable("id") Integer id) {
        System.out.println("PUT" + id);
        return SUCCESS;
    }

}

4、@RequestParam

SpringMVC通过分析处理方法的签名，将HTTP请求信息绑定到处理方法相应的形参中。
SpringMVC对控制器处理方法签名的限制是很宽松的，几乎可以按照喜欢的任何方法对方法进行签名。
必要是可以对方法、方法形参标注相应的注解：@PathVariable、@RequestParam、@RequestHeader等。SpringMVC会将HTTP请求的信息绑定到相应的方法形参中，并根据方法的返回值类型作出相应的后续处理。

  package com.xianhuii;

  import org.springframework.stereotype.Controller;
  import org.springframework.web.bind.annotation.*;

  @Controller
  @RequestMapping("/springmvc")
  public class RequestMappingTest01 {
      private static final String SUCCESS = "success";

      /**
       * @RequestParam映射请求参数：
       *      value：请求参数的参数名
       *      required：该参数是否必须，默认为true
       *      defaultValue：请求参数的默认值
       * @param name
       * @param age
       * @return
       */
      @RequestMapping("/testRequestParam")
      public String testRequestParam(
              @RequestParam(value = "username", required = false) String name, 
              @RequestParam(value = "age", required = false, defaultValue = "0") int age) {
          System.out.println("username: " + name + ", age: " + age);
          return SUCCESS;
      }

  }

5、@RequestHeader

映射请求头信息。

package com.xianhuii;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

@Controller
@RequestMapping("/springmvc")
public class RequestMappingTest01 {
    private static final String SUCCESS = "success";

    @RequestMapping("/testRequestHeader")
    public String testRequestHeader(@RequestHeader("Accept-Language") String val) {
        System.out.println("testRequestHeader: " + val);
        return SUCCESS;
    }

}

6、@CookieValue

绑定请求中的Cookie值。

package com.xianhuii;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

@Controller
@RequestMapping("/springmvc")
public class RequestMappingTest01 {
    private static final String SUCCESS = "success";

    /**
     * @CookieValue：映射一个Cookie值。
     * @param sessionId
     * @return
     */
    @RequestMapping("testCookieValue")
    public String testCookieValue(@CookieValue("JSESSIONID") String sessionId) {
        System.out.println("testCookieValue: " + sessionId);
        return SUCCESS;
    }

}

7、使用POJO对象绑定请求参数值

SpringMVC会按照请求参数名和POJO属性名进行自动匹配，自动为该对象填充属性值。支持级联属性。

POJO（User）：

package com.xianhuii.entities;

public class User {
    private String username;
    private String password;
    private String email;
    private int age;
    private Address address;

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public int getAge() {
        return age;
    }

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

    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

    @Override
    public String toString() {
        return "User{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", email='" + email + '\'' +
                ", age=" + age +
                ", address=" + address +
                '}';
    }

}

POJO（Address）：

package com.xianhuii.entities;

public class Address {
    private String province;
    private String city;

    public String getProvince() {
        return province;
    }

    public void setProv***ring province) {
        this.province = province;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    @Override
    public String toString() {
        return "Address{" +
                "province='" + province + '\'' +
                ", city='" + city + '\'' +
                '}';
    }

}

前端：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>

  <head>
    <title>$Title$</title>
  </head>

  <body>

  <form action="/springmvc/testPOJO" method="post">
    <p>username: <input type="text" name="username"></p>
    <p>password: <input type="password" name="password"></p>
    <p>email: <input type="text" name="email"></p>
    <p>age: <input type="text" name="age"></p>
    <p>city: <input type="text" name="address.city"></p>
    <p>province: <input type="text" name="address.province"></p>
    <p><input type="submit" value="Submit"></p>
  </form>

  </body>
</html>

Controller：

package com.xianhuii;

import com.xianhuii.entities.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;

@Controller
@RequestMapping("/springmvc")
public class RequestMappingTest01 {
    private static final String SUCCESS = "success";

    @RequestMapping("/testPOJO")
    public String testPojo(User user) {
        System.out.println(user);
        return SUCCESS;
    }

}

8、使用Servlet API作为形参

  package com.xianhuii;

  import com.xianhuii.entities.User;
  import org.springframework.stereotype.Controller;
  import org.springframework.web.bind.annotation.*;

  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;

  @Controller
  @RequestMapping("/springmvc")
  public class RequestMappingTest01 {
      private static final String SUCCESS = "success";

      /**
       * 可以使用Servlet原生API作为目标方法的参数：
       *      HttpServletRequest
       *      HttpServletResponse
       *      HttpSession
       *      java.security.Principal
       *      Locale
       *      InputStream
       *      OutputStream
       *      Reader
       *      Writer
       * @param request
       * @param response
       * @return
       */
      @RequestMapping("/testServletAPI")
      public String testServletAPI(HttpServletRequest request,
                                   HttpServletResponse response) {
          return SUCCESS;
      }
  }