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01-06、校验器

发布于 2025-03-09 23:21:25 字数 12468 浏览 0 评论 0 收藏 0

校验器，Validator。

在处理带有表单数据的 HTTP 请求时，通常这样做：

if (表单数据符合要求) {
  处理数据，返回结果；
} else {
  返回结果，提示用户重新输入数据；
}

判断表单数据是否符合要求这就是校验器该做的事情。我们可以自己编写校验类，也可以使用 Spring MVC 自带的相关类。

将表单数据绑定到对象中

项目结构如下：

源码

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
  <context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/applicationContext.xml</param-value>
  </context-param>
  <listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
  </listener>
  <servlet>
    <servlet-name>dispatcher</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <load-on-startup>2</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>dispatcher</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>
  <session-config>
    <session-timeout>
      30
    </session-timeout>
  </session-config>
  <welcome-file-list>
    <welcome-file>redirect.jsp</welcome-file>
  </welcome-file-list>
</web-app>

applicationContext.xml

<?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:p="http://www.springframework.org/schema/p"
     xmlns:aop="http://www.springframework.org/schema/aop"
     xmlns:tx="http://www.springframework.org/schema/tx"
     xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
     http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
     http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd">

</beans>

dispatcher-servlet.xml

<?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:p="http://www.springframework.org/schema/p"
     xmlns:aop="http://www.springframework.org/schema/aop"
     xmlns:tx="http://www.springframework.org/schema/tx"
     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-4.0.xsd
     http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd
     http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd
     http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd
     http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">

  <context:component-scan base-package="me.letiantian.controller" />
  <mvc:annotation-driven/>

  <bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>

  <bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <property name="mappings">
      <props>
        <prop key="index">indexController</prop>
      </props>
    </property>
  </bean>

  <bean id="viewResolver"
      class="org.springframework.web.servlet.view.InternalResourceViewResolver"
      p:prefix="/WEB-INF/jsp/"
      p:suffix=".jsp" />

  <bean name="indexController"
      class="org.springframework.web.servlet.mvc.ParameterizableViewController"
      p:viewName="index" />

</beans>

hello/input.jsp

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>JSP Page</title>
  </head>
  <body>
    <form method="POST" action="${pageContext.request.contextPath}/hello/output">
      First Name: <input type="text" name="firstName"> <br/>
      Second Name: <input type="text" name="secondName"> <br/>
      <input type="submit" />

    </form>
  </body>
</html>

hello/output.jsp

<%@page contentType="text/plain" pageEncoding="UTF-8"%>
first name: ${person.firstName}
second name: ${person.secondName}

Person.java

package me.letiantian.form;

public class Person {

  private String firstName;
  private String secondName;

  public String getFirstName() {
    return firstName;
  }

  public void setFirstName(String firstName) {
    this.firstName = firstName;
  }

  public String getSecondName() {
    return secondName;
  }

  public void setSecondName(String secondName) {
    this.secondName = secondName;
  }

}

HelloController.java

package me.letiantian.controller;

import java.io.PrintWriter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import me.letiantian.form.Person;
import org.springframework.web.bind.annotation.ModelAttribute;

@Controller
@RequestMapping("/hello")
public class HelloController{

  @RequestMapping(value = "")
  public String index() {
    return "index";
  }

  @RequestMapping(value = "/input")
  public String input() {
    return "hello/input";
  }

  @RequestMapping(value = "/output")
  public String output(Person person, Model model) {
    model.addAttribute("person", person);
    return "hello/output";
  }

//  @RequestMapping(value = "/output")
//  public String output(@ModelAttribute(value="person") Person person, Model model) {
//    return "hello/output";
//  }

}

注意，

  @RequestMapping(value = "/output")
  public String output(Person person, Model model) {
    model.addAttribute("person", person);
    return "hello/output";
  }

和

  @RequestMapping(value = "/output")
  public String output(@ModelAttribute(value="person") Person person, Model model) {
    return "hello/output";
  }

是一样的。

浏览器访问

表单填入信息：

提交表单后：

校验数据

hello/input.jsp 修改如下

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title> JSP Page</title>
    <style type="text/css">
      .error {color: red;}
    </style>
  </head>
  <body>

    <form:form modelAttribute="person" method="POST" action="${pageContext.request.contextPath}/hello/output">
      firstName: <form:input path="firstName" /> <form:errors path="firstName" cssClass="error"/> <br/>
      secondName: <form:input path="secondName" /> <form:errors path="secondName" cssClass="error"/> <br/>
      <input type="submit" value="提交" />
    </form:form>

  </body>
</html>

注意 <form:form modelAttribute="person" 。

HelloController.java 修改如下

package me.letiantian.controller;

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

import me.letiantian.form.Person;
import me.letiantian.validator.PersonValidator;
import org.springframework.validation.BindingResult;

@Controller
@RequestMapping("/hello")
public class HelloController{

  @RequestMapping(value = "")
  public String index() {
    return "index";
  }

  @RequestMapping(value = "/input")
  public String input(Model model) {
    model.addAttribute("person", new Person());  // 很重要
    return "hello/input";
  }

  @RequestMapping(value = "/output")
  public String output(Person person, BindingResult bindingResult, Model model) {
    model.addAttribute("person", person);  // 很重要
    PersonValidator pv = new PersonValidator();
    pv.validate(person, bindingResult);

    if (bindingResult.hasErrors()) {  // 如果有错误,BindingResult 是 Errors 的子类
      return "hello/input";
    }

    return "hello/output";

  }

}

注意每个方法中的 model.addAttribute("person") 是和 hello/input.jsp 中的 <form:form modelAttribute="person" 对应的。

添加 PersonValidator.java

该文件在包 me.letiantian.validator 下，内容为：

package me.letiantian.validator;

import me.letiantian.form.Person;
import org.springframework.validation.Errors;
import org.springframework.validation.Validator;
import org.springframework.validation.ValidationUtils;

public class PersonValidator implements Validator{

  @Override
  public boolean supports(Class<?> type) {
    return Person.class.isAssignableFrom(type);
  }

  @Override
  public void validate(Object o, Errors errors) {
    Person person = (Person) o;
    ValidationUtils.rejectIfEmptyOrWhitespace(errors, "firstName", null, "firstName 不能为空");
    ValidationUtils.rejectIfEmptyOrWhitespace(errors, "secondName", null, "secondName 不能为空");
    if (person.getFirstName().length() < 2) {
      errors.rejectValue("firstName", null, "firstName 太短");
    }
  }
}

测试

第 1 组：


第 2 组：


第 3 组：


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