SSM-4-数据绑定

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<dependency>
    <groupId>jstl</groupId>
    <artifactId>jstl</artifactId>
    <version>1.2</version>
</dependency>
<dependency>
    <groupId>taglibs</groupId>
    <artifactId>standard</artifactId>
    <version>1.1.2</version>
</dependency>

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<filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>UTF-8</param-value>
    </init-param>
    <init-param>
        <param-name>forceEncoding</param-name>
        <param-value>true</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

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@Controller
@RequestMapping("/four")
public class FourController {
    private static final Log logger = LogFactory.getLog(FourController.class);

    private final FourUserService fourUserService;
    @Autowired
    public FourController(FourUserService fourUserService) {
        this.fourUserService = fourUserService;
    }

    /**
     * 第一次加载表单会触发这个方法
     */
    @RequestMapping("/input")
    public String inputUser(Model model) {
        HashMap<String, String> hobbys = getMap();
		// 虽然是第一次加载，但是也要在model添加一个领域模型的对象，否则表单标签无法找到modelAttribute属性指定的form backing object
        model.addAttribute("user", new User());
        
        model.addAttribute("hobbys", hobbys);
        model.addAttribute("carrers", new String[]{"教师", "学生", "码农", "民工"});
        model.addAttribute("houseRegister", new String[]{"北京", "上海", "广州", "深圳"});
        return "userAdd";
    }

    /**
     * 表单提交的时候会触发这个方法
     */
    @RequestMapping("/save")
    public String addUser(@ModelAttribute User user, Model model) {
        // 进入业务层验证业务逻辑
        if (fourUserService.addUser(user)) {
            logger.info("成功");
            // 重定向到本控制器里的list控制方法
            return "redirect:list";
        }
        logger.info("失败");
        // 验证失败的时候就到了这里，相当于重新加载，但是会带着已经填过的数据，用户就不用再次填写已经填写过的输入，注意这里没有在model.addAttribute()中new bean()。看不懂请对比上面的input方法
        HashMap<String, String> hobbys = getMap();
        model.addAttribute("hobbys", hobbys);
        model.addAttribute("carrers", new String[]{"教师", "学生", "码农", "民工"});
        model.addAttribute("houseRegister", new String[]{"北京", "上海", "广州", "深圳"});
        return "userAdd";
    }

    @RequestMapping("/list")
    public String listUsers(Model model) {
        List<User> users = fourUserService.getUsers();
        model.addAttribute("users", users);
        return "userList";
    }

    private HashMap<String, String> getMap() {
        HashMap<String, String> hobbys = new HashMap<>(5);
        hobbys.put("篮球", "篮球");
        hobbys.put("乒乓球", "乒乓球");
        hobbys.put("电玩", "电玩");
        hobbys.put("游泳", "游泳");
        return hobbys;
    }
}

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package service.four;

import org.springframework.stereotype.Service;
import po.four.User;

import java.util.ArrayList;

/**
 * @author pr919
 */
@Service
public class FourUserServiceImpl implements FourUserService {
    private static ArrayList<User> users = new ArrayList<>();

    @Override
    public boolean addUser(User u) {
        String magicValue = "民工";
        if (!magicValue.equals(u.getCarrer()) && !"".equals(u.getUsername())){
            users.add(u);
            return true;
        }
        return false;
    }

    @Override
    public ArrayList<User> getUsers() {
        return users;
    }
}

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<%-- userAdd.jsp --%>

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<%--
  Created by IntelliJ IDEA.
  User: pr919
  Date: 2019.6.24
  Time: 14:41
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" %>
<%@ page isELIgnored="false" %>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
%>
<html>
<head>
    <base href="<%=basePath%>"/>
    <title>dataBind</title>
</head>
<body>
<%--@elvariable id="user" type="po.four.User"--%>
<form:form modelAttribute="user" mothod="post" action="four/save">
    <fieldset>
        <legend>添加一个用户</legend>
        <p>
            <label>用户名：</label>
            <form:input path="username"/>
        </p>
        <p>
            <label>爱好：</label>
            <%--@elvariable id="hobbys" type="java.util.List"--%>
            <form:checkboxes items="${hobbys}" path="hobby"/>
        </p>
        <p>
            <label>朋友：</label>
            <form:checkbox path="friends" value="张三"/>1
            <form:checkbox path="friends" value="李四"/>2
            <form:checkbox path="friends" value="王五"/>3
            <form:checkbox path="friends" value="赵六"/>4
        </p>

        <p>
            <label>职业：</label>
            <form:select path="carrer">
                <option></option>
                请选择职业
                <%--@elvariable id="carrers" type="java.util.List"--%>
                <form:options items="${carrers}"/>
            </form:select>
        </p>
        <p>
            <label>户籍：</label>
            <form:select path="houseRegister">
                <option></option>
                请选择户籍
                <%--@elvariable id="houseRegister" type="java.util.List"--%>
                <form:options items="${houseRegister}"/>
            </form:select>
        </p>
        <p>
            <label>个人描述：</label>
            <form:textarea path="remark" rows="5"/>
        </p>
        <p id="buttons">
            <input id="reset" type="reset" />
            <input id="submit" type="submit" value="添加">
        </p>
    </fieldset>
</form:form>
</body>
</html>

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<%-- userAdd.jsp --%>

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%--
  Created by IntelliJ IDEA.
  User: pr919
  Date: 2019.6.24
  Time: 15:18
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" %>
<%@ page isELIgnored="false" %>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
%>
<html>
<head>
    <base href="<%=basePath%>"/>
    <title>dataList</title>
</head>
<body>
<h1>用户列表</h1>
<a href="<c:url value="four/input"/>">继续添加</a>
<table>
    <tr>
        <th>用户名</th>
        <th>兴趣爱好</th>
        <th>朋友</th>
        <th>职业</th>
        <th>户籍</th>
        <th>个人描述</th>
    </tr>

    <c:forEach items="${users}" var="user">
        <tr>
            <td>${user.username}</td>
            <td>
                <c:forEach items="${user.hobby}" var="hobby">
                    ${hobby}&nbsp;
                </c:forEach>
            </td>
            <td>
                <c:forEach items="${user.friends}" var="friend">
                    ${friend}&nbsp;
                </c:forEach>
            </td>
            <td>${user.carrer}</td>
            <td>${user.houseRegister}</td>
            <td>${user.remark}</td>
        </tr>
    </c:forEach>
</table>
</body>
</html>