请求参数的绑定说明

1.绑定机制

只需要在方法中的参数写上变量名与参数名相同的形参，即可自动获取。
底层实现：通过反射获取形参的名字，再如servlet那样通过request获取参数。

2.支持的数据类型

基本数据类型和字符串类型
实体类型(JavaBean)
集合数据类型(List、map集合等)

封装JavaBean

Account类(其中包含User类)

package com.czy.domain;

import java.io.Serializable;

public class Account implements Serializable {
    private String username;
    private String password;
    private Double money;

    private User user;

    public User getUser() {
        return user;
    }

    @Override
    public String toString() {
        return "Account{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", money=" + money +
                ", user=" + user +
                '}';
    }

    public void setUser(User user) {
        this.user = user;
    }

    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 Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }
}

User类

package com.czy.domain;

import java.io.Serializable;

public class User implements Serializable {
    private String uname;
    private Integer age;

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

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    public Integer getAge() {
        return age;
    }

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

表单(注意user的项目)

    <form method="post" action="param/saveAccount">
        <label for="username">姓名:</label>
        <input id="username" name="username"><br>
        <label for="password">密码:</label>
        <input type="password" name="password" id="password"><br>
        <label for="money">金额:</label>
        <input type="text" id="money" name="money"><br>
        <label for="uname">用户姓名:</label>
        <input id="uname" name="user.uname"><br>  <!--user.uname封装进user中-->
        <label for="age">用户年龄:</label>  <!--同上-->
        <input id="age" name="user.age"><br>
        <input type="submit" value="提交">
    </form>

Controller接收自动封装

    @RequestMapping("/saveAccount")
    public String saveAccount(Account account){
        System.out.println(account);
        return "success";
    }

集合数据封装

Account类

package com.czy.domain;

import java.io.Serializable;
import java.util.List;
import java.util.Map;

public class Account implements Serializable {
    private String username;
    private String password;
    private Double money;

    private List<User> users;

    private Map<String,User> map;

    public Map<String, User> getMap() {
        return map;
    }

    public void setMap(Map<String, User> map) {
        this.map = map;
    }

    public List<User> getUsers() {
        return users;
    }

    public void setUsers(List<User> users) {
        this.users = users;
    }

    @Override
    public String toString() {
        return "Account{" +
                "username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", money=" + money +
                ", users=" + users +
                ", map=" + map +
                '}';
    }


    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 Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }
}

前台表单

    <form method="post" action="param/saveAccount">
        <label for="username">姓名:</label>
        <input id="username" name="username"><br>
        <label for="password">密码:</label>
        <input type="password" name="password" id="password"><br>
        <label for="money">金额:</label>
        <input type="text" id="money" name="money"><br>

        <label for="uname1">用户姓名:</label>
        <input id="uname1" name="users[0].uname"><br>
        <label for="age1">用户年龄:</label>
        <input id="age1" name="users[0].age"><br>

        <label for="uname2">用户姓名:</label>
        <input id="uname2" name="map['one'].uname"><br>
        <label for="age2">用户年龄:</label>
        <input id="age2" name="map['one'].age"><br>

        <input type="submit" value="提交">
    </form>

3.过滤器解决中文乱码

web.xml中配置过滤器

  <filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

特殊情况——自定义类型转换器

我们从前台的数据提交上来的都是String，MVC通过内置的类型转换器帮我们转换成对应的类型，存入JavaBean/参数中。但是有时某些形式的数据，会导致存储失败，比如说：日期形式2020/2/2可以存储，而2020-2-2无法存储或前台表单type=date也无法存储。
故我们需要自定义类型转换器解决该问题

步骤一：实现Converter接口

package com.czy.utils;

import org.springframework.core.convert.converter.Converter;

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

/**
 * 把字符串转换为日期
 */
public class StringToDateConverter implements Converter<String, Date> {
    @Override
    public Date convert(String s) {
        if(s == null){
            throw new RuntimeException("传参为空");
        }
        DateFormat format = new SimpleDateFormat("yyyy-MM-dd");
        try {
            return format.parse(s);
        } catch (ParseException exception) {
            throw new RuntimeException("数据类型转换错误");
        }
    }
}

步骤二:注册自定义类型转换器

在springmvc.xml配置文件中配置

    <!--开启SpringMVC框架注解的支持-->
    <mvc:annotation-driven conversion-service="factoryBean"></mvc:annotation-driven>

    <!--配置自定义类型转换器-->
    <bean id="factoryBean" class="org.springframework.context.support.ConversionServiceFactoryBean">
        <property name="converters">
            <set>
                <bean class="com.czy.utils.StringToDateConverter"></bean>
            </set>
        </property>
    </bean>