Spring MVC 表單控制器 SimpleFormController 完整指南

簡介

在 Spring MVC 中處理表單提交是常見需求。傳統做法可能需要分別繼承 AbstractController 顯示表單，繼承 AbstractCommandController 處理表單，但這會導致維護兩個控制器。SimpleFormController 正是為了解決這個問題而設計：它自動處理 GET 請求顯示表單、POST 請求處理提交，並在驗證失敗時自動重新顯示表單讓用戶修正錯誤。

核心組件

表單對應的 POJO

首先定義一個簡單的命令對象（表單對象）來承載表單數據：

package model;

public class Student {
    private String name;
    private String sex;

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getSex() { return sex; }
    public void setSex(String sex) { this.sex = sex; }
}

控制器實現

繼承 SimpleFormController 並覆寫關鍵方法：

package Action;

import model.Student;
import org.springframework.validation.BindException;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.mvc.SimpleFormController;

public class RegisterStudentController extends SimpleFormController {

    public RegisterStudentController() {
        this.setCommandClass(Student.class);
    }

    protected ModelAndView onSubmit(Object object, BindException arg1) throws Exception {
        Student stu = (Student) object;
        return new ModelAndView(getSuccessView(), "student", stu);
    }
}

注意：onSubmit() 可返回 ModelAndView 向成功頁面傳遞數據，而 doSubmitAction() 不能返回數據，兩者同時只有一個生效。

配置文件

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
    xmlns="https://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="https://java.sun.com/xml/ns/j2ee
    https://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/train-service.xml,/WEB-INF/train-data.xml,/WEB-INF/train-servlet.xml</param-value>
    </context-param>
    <servlet>
        <servlet-name>train</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>0</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>train</servlet-name>
        <url-pattern>*.mvc</url-pattern>
    </servlet-mapping>
    <filter>
        <filter-name>character</filter-name>
        <filter-class>Action.CharacterFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>character</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

train-servlet.xml

定義控制器 Bean 並配置表單視圖與成功視圖：

<bean id="RegisterStudentController" class="Action.RegisterStudentController">
    <property name="formView">
        <value>register</value>
    </property>
    <property name="successView">
        <value>success</value>
    </property>
</bean>
<bean id="simpleUrlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <property name="mappings">
        <props>
            <prop key="/home.mvc">HomeController</prop>
            <prop key="/register.mvc">RegisterStudentController</prop>
        </props>
    </property>
</bean>

視圖頁面

register.jsp（表單頁）

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">
    <title>學生註冊</title>
</head>
<body>
    <form action="<%=request.getContextPath() %>/register.mvc" method="post">
        姓名：<input type="text" name="name"/><br/>
        性別：<input type="text" name="sex"/><br/>
        <input type="submit" value="提交"/>
    </form>
</body>
</html>

success.jsp（成功頁）

<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
    <base href="<%=basePath%>">
    <title>註冊成功</title>
</head>
<body>
    ${student.name}-----${student.sex} <br>
</body>
</html>

運行測試

啟動應用後訪問 /register.mvc，填寫表單提交，成功頁將顯示提交的學生信息。文中也提到使用 Filter 處理中文編碼問題。