Spring MVC 表单验证

1. 基于 JSR-303(一个数据验证的规范):

import javax.validation.constraints.Min;
import javax.validation.constraints.NotNull;
import org.hibernate.validator.constraints.NotBlank;

public class User {

    private String username;

    private String password;

    private int age;

    @NotBlank(message="用户名不能为空")
    public String getUsername() {
       return username;
    }

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

    @NotNull(message="密码不能为null")
    public String getPassword() {
       return password;
    }

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

    @Min(value=10, message="年龄的最小值为10")
    public int getAge() {
       return age;
    }

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

}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
     http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
     http://www.springframework.org/schema/context
     http://www.springframework.org/schema/context/spring-context-3.0.xsd
     http://www.springframework.org/schema/mvc
     http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

    <mvc:annotation-driven/>
</beans>

import javax.validation.Valid;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class UserController {

    @RequestMapping("login")
    public String login(@Valid User user, BindingResult result) {
       if (result.hasErrors())
           return "user/login";
       return "redirect:/";
    }

}

使用@NotBlank等注解，然后在要验证的地方使用@Valid 标签。最后验证的结果是在BindingResult 获取，注意据说result 要紧挨着前面的@Valid，而且是一个验证一个BindingResult参数。

2. 还有就是继承Validator 接口。