SpringMVC 学习（三）——映射请求参数 & 请求参数

请求处理方法签名

•Spring MVC 通过分析处理方法的签名，将 HTTP 请求信 息绑定到处理方法的相应人参中。

•Spring MVC 对控制器处理方法签名的限制是很宽松的， 几乎可以按喜欢的任何方式对方法进行签名。

•必要时可以对方法及方法入参标注相应的注解（

@PathVariable

、@RequestParam、@RequestHeader 等）、Spring

MVC 框架会将 HTTP 请求的信息绑定到相应的方法入参 中，并根据方法的返回值类型做出相应的后续处理。

 

 

使用 @RequestParam 绑定请求参数值

•在处理方法入参处使用 @RequestParam 可以把请求参 数传递给请求方法

–value：参数名

–required：是否必须。默认为 true, 表示请求参数中必须包含对应 的参数，若不存在，将抛出异常

 

使用 @RequestHeader 绑定请求报头的属性值

•请求头包含了若干个属性，服务器可据此获知客户端的信 息，通过 @RequestHeader 即可将请求头中的属性值绑 定到处理方法的入参中

 

 

使用 @CookieValue 绑定请求中的 Cookie 值

•@CookieValue 可让处理方法入参绑定某个 Cookie 值

 

 

使用 POJO 对象绑定请求参数值

•Spring MVC 会按请求参数名和 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。

如：dept.deptId、dept.address.tel 等

 

 

使用 Servlet API 作为入参

 

MVC 的 Handler 方法可以接受哪些 ServletAPI 类型的参数

•HttpServletRequest

•HttpServletResponse

•HttpSession

•java.security.Principal

•Locale

•InputStream

•OutputStream

•Reader

•Writer

代码示例：

address.java

package com.xuehj.springmvc.entity;

/**
 * @program: SpringMVC-1
 * @description: TODO
 * @author: Mr.Xue
 * @create: 2018-12-24 19:13
 **/
public class Address {
    private String province;
    private String city;

    public String getProvince() {
        return province;
    }

    public void setProvince(String 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 + "]";
    }
}

user.java

package com.xuehj.springmvc.entity;

/**
 * @program: SpringMVC-1
 * @description: TODO
 * @author: Mr.Xue
 * @create: 2018-12-24 19:13
 **/
public class User {
    private Integer id;

    private String username;
    private String password;

    private String email;
    private int age;

    private Address address;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    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{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", email='" + email + '\'' +
                ", age=" + age +
                ", address=" + address +
                '}';
    }
}

test.java

package com.xuehj.springmvc.handler;

import com.xuehj.springmvc.entity.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.CookieValue;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.Writer;

/**
 * @program: SpringMVC
 * @description: TODO
 * @author: Mr.Xue
 * @create: 2018-12-24 09:36
 **/
@Controller
@RequestMapping("/view")
public class HelloWorld {

    /**
     * @RequestParam 来映射请求参数.
     * value 值即请求参数的参数名
     * required 该参数是否必须. 默认为 true
     * defaultValue 请求参数的默认值
     * int age 改成 Integer 比较好，有 null 值
     */
    @RequestMapping(value = "/testRequestParam")
    public String testRequestParam(
            @RequestParam(value = "username") String un,
            @RequestParam(value = "age", required = false, defaultValue = "0") int age) {
        System.out.println("testRequestParam, username: " + un + ", age: "
                + age);
        return "success.jsp";
    }

    /**
     * 了解:
     * 映射请求头信息 用法同 @RequestParam
     */
    @RequestMapping("/testRequestHeader")
    public String testRequestHeader(
            @RequestHeader(value = "Accept-Language") String al) {
        System.out.println("testRequestHeader, Accept-Language: " + al);
        return "success.jsp";
    }

    /**
     * 了解:
     *
     * @CookieValue: 映射一个 Cookie 值. 属性同 @RequestParam
     */
    @RequestMapping("/testCookieValue")
    public String testCookieValue(@CookieValue("JSESSIONID") String sessionId) {
        System.out.println("testCookieValue: sessionId: " + sessionId);
        return "success.jsp";
    }

    /**
     * Spring MVC 会按请求参数名和 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。
     * 如：dept.deptId、dept.address.tel 等
     */
    @RequestMapping("/testPojo")
    public String testPojo(User user) {
        System.out.println("testPojo: " + user);
        return "success.jsp";
    }

    /**
     * 可以使用 Serlvet 原生的 API 作为目标方法的参数 具体支持以下类型
     * <p>
     * HttpServletRequest
     * HttpServletResponse
     * HttpSession
     * java.security.Principal
     * Locale InputStream
     * OutputStream
     * Reader
     * Writer
     *
     * @throws IOException
     */
    @RequestMapping("/testServletAPI")
    public void testServletAPI(HttpServletRequest request,
                               HttpServletResponse response, Writer out) throws IOException {
        System.out.println("testServletAPI, " + request + ", " + response);
        out.write("hello springmvc");
        //return "success.jsp";
    }
}

index.jsp

<%--
  Created by IntelliJ IDEA.
  User: 薛恒杰
  Date: 2018/12/24
  Time: 9:21
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
    <head>
        <title>$Title$</title>
    </head>
    <body>
        <a href="view/testRequestParam?username=Xue&age=20">Test RequestParam</a>
        <br><br>

        <a href="view/testRequestHeader">Test RequestHeader</a>
        <br><br>

        <a href="view/testCookieValue">Test CookieValue</a>
        <br><br>

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

        <a href="view/testServletAPI">Test ServletAPI</a>
        <br><br>
    </body>
</html>