SpringMVC系列（四）使用 POJO 對象綁定請求參數值

在實際開發中如果參數太多就不能使用@RequestParam去一個一個的映射了，需要定義一個實體參數對象(POJO)來映射請求參數。Spring MVC 會按請求參數名和 POJO 屬性名進行自動匹配，自動為該對象填充屬性值。支持級聯屬性。如：address.province、address.city等。

具體步驟如下：

1.定義需要的請求參數的實體

User.java

package com.study.springmvc.model;

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 + "]";
    }

}

Address.java

package com.study.springmvc.model;

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 + "]";
    }
    
}

2. 在index.jsp頁面編寫傳參的表單

<!--POJO測試 begin  --> 
<br>
<form action="pojoTest/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>
<!--POJO測試 end  --> 

3.編寫handler

PojoTest.java

package com.study.springmvc.handlers;

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

import com.study.springmvc.model.User;

@RequestMapping("/pojoTest")
@Controller
public class PojoTest {

    public static final String SUCCESS="success";
    
    /**
     * Spring MVC 會按請求參數名和 POJO 屬性名進行自動匹配，
     * 自動為該對象填充屬性值。支持級聯屬性。
     * 如：address.province、address.city等。
     */
    @RequestMapping("/testPojo")
    public String testPojo(User user) {
        System.out.println("testPojo: " + user);
        return SUCCESS;
    }
}