今天我们将谈谈前端form表单参数如何透过@RequestMapping与后台的Java Bean (POJO)绑定。
本文以前面两篇博客《Spring boot （一）：快速构建Spring Boot 1.5.8 maven Web 项目》《Spring boot（二）：HTTPS之自签名证书配置》为基础，代码基于SpringBootBase工程。
首先来写个简单的登录界面表单代码index.html，界面非常简单，两个输入框，一个登录按钮：
<!DOCTYPE html>
<html lang="zh-cn">
<head>
<meta charset="utf-8"/>
<title>Login</title>
<link rel="stylesheet" href="/SpringBootBase/css/bootstrap.min.css"/>
<link rel="stylesheet" href="/SpringBootBase/css/customer/login.css"/>
</head>
<body>
<div class="container">
<form class="form-signin" action="./login" method="post">
<h2 class="form-signin-heading">请 登 录</h2>
<input type="text" class="form-control" placeholder="账号" name="username"/>
<input type="password" class="form-control" placeholder="密码" name="password"/>
<button class="btn btn-lg btn-primary btn-block" type="submit">登录</button>
</form>
</div>
</body>
</html>
再来写个POJO视图对象UserVO
public class UserVO {
public String username;
public String password;
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;
}
@Override
public String toString() {
return "username: " + username + ", password: " + password;
}
}
再写个controller
@Controller
public class LoginController {
@RequestMapping(value = "login", method = RequestMethod.POST)
public String login(UserVO user){
System.out.println("POJO: " + user.getClass().getName() +
", hash code: " + user.hashCode() + ", " + user.toString());
return "redirect:/";
}
}
启动Tomcat service，在地址栏输入https://localhost:8443/SpringBootBase/ 显示如下界面，
图1
输入账号admin及密码123456，在控制台可见输出如下log
POJO: tech.onroad.springbootbase.bean.UserVO, hash code: 1036686981, username: admin, password: 123456
说明前端表单传过来的两个参数username, password会自动绑定到UserVO这个POJO上。其实这都是Spring @RequestMapping这个注解的功劳，它会自动扫描形参的POJO，并创建对象，如果前端传进来的参数与POJO成员变量名相同，会通过POJO的setter方法传给该对象。
Q & A
1. 匹配参数里是否会忽略对象成员变量的大小写？
我们将UserVO的成员变量username改写为userName,即
public class UserVO {
private String userName;
private String password;
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;
}
@Override
public String toString() {
return "userName: " + userName + ", password: " + password;
}
}
Controller代码不变
再次运行一下，同样输入账号admin及密码123456，得到的log为：
POJO: tech.onroad.springbootbase.bean.UserVO, hash code: 1762238496, userName: null, password: 123456
userName的值为空，很显然在匹配过程中是区分大小写的。
2. 如果形参有两个POJO对象，它们刚好都有一个username的成员变量，那又会如何匹配呢？
同样我们通过代码来验证一下：
首先，我们增加一个StudentVO POJO, 该对象有一个成员变量也叫username,
public class StudentVO {
private String username;
private int age;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "username: " + username + ", age: " + age;
}
}
controller login方法更改为
@Controller
public class LoginController {
@RequestMapping(value = "login", method = RequestMethod.POST)
public String login(UserVO user, StudentVO student){
System.out.println("POJO: " + user.getClass().getName() +
", hash code: " + user.hashCode() + ", " + user.toString());
System.out.println("POJO: " + student.getClass().getName() +
", hash code: " + student.hashCode() + ", " + student.toString());
return "redirect:/";
}
}
运行， 同样输入账号admin及密码12345，得到如下log
POJO: tech.onroad.springbootbase.bean.UserVO, hash code: 1260683413, userame: admin, password: 123456
POJO: tech.onroad.springbootbase.bean.StudentVO, hash code: 816397424, username: admin, age: 0
说明只要形参的成员变量名与前端传递进来的参数名一致，都会通过setter方法将参数传给对应Java bean的成员变量。
完整代码可到我的github下载:
https://github.com/onroadtech/SpringbootBase/
branch: master
commit-id: 94dd507dfc9c71e62e1b0f3b19f54843c583d84e
本博文已同步发表于我的个人博客网站，欢迎转载指正并注明出处。
个人博客： www.onroad.tech
指正邮箱： onroad_tech@163.com
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