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。
## [](https://github.com/someus/another-tutorial-about-java-web/blob/master/01-06.md#将表单数据绑定到对象中)将表单数据绑定到对象中
项目结构如下：
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/01.png)
### [](https://github.com/someus/another-tutorial-about-java-web/blob/master/01-06.md#源码)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。
### [](https://github.com/someus/another-tutorial-about-java-web/blob/master/01-06.md#浏览器访问)浏览器访问
表单填入信息：
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/02.png)
提交表单后：
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/03.png)
## [](https://github.com/someus/another-tutorial-about-java-web/blob/master/01-06.md#校验数据)校验数据
### [](https://github.com/someus/another-tutorial-about-java-web/blob/master/01-06.md#helloinputjsp修改如下)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"`。
### [](https://github.com/someus/another-tutorial-about-java-web/blob/master/01-06.md#hellocontrollerjava修改如下)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。
### [](https://github.com/someus/another-tutorial-about-java-web/blob/master/01-06.md#添加personvalidatorjava)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");
}
}
}
~~~
### [](https://github.com/someus/another-tutorial-about-java-web/blob/master/01-06.md#测试)测试
**第1组：**
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/04.png)
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/05.png)
**第2组：**
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/06.png)
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/07.png)
**第3组：**
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/08.png)
[](https://github.com/someus/another-tutorial-about-java-web/blob/master/img/01-06/09.png)
- JSP & Servlet
- 00-00、序
- 00-01、相关软件的安装
- 00-02、理解HTTP
- 00-03、从JSP开始
- 00-04、理解Servlet
- 00-05、过滤器与监听器
- 00-06、使用velocity模板引擎
- 00-07、使用数据库连接池
- 00-08、Tomcat的运行机制
- Spring MVC
- 01-00、Spring与依赖注入
- 01-01、Spring与面向切面编程
- 01-02、使用Spring MVC构建Hello World
- 01-03、JdbcTemplate
- 01-04、基于注解的URL映射
- 01-05、JSON
- 01-06、校验器
- 01-07、国际化
- 01-08、拦截器
- 01-09、文件上传
- 01-10、转换器与格式化
- Book
- Online Tutorial
- Q & A
- Learn More
- Supplement