简介

数据绑定是将用户参数输入值绑定到领域模型的一种特性。在Spring MVC的Controller和View参数数据传递中，所有HTTP请求参数的类型均为字符串。如果模型需要绑定的类型为double或int，则需要手动进行类型转换。而有了数据绑定后，就不再需要手动将HTTP请求中String类型转换为模型需要的类型。数据绑定的另一个好处是，当输入验证失败时，会重新生成一个HTML表单，无需重新填入输入字段

在Spring MVC中，为了方便 高效的使用数据绑定，还需要学习表单标签库

表单标签库

表单标签库中包含可以用在JSP页面中渲染HTML元素的标签，JSP页面使用Spring表单标签库时，必须在JSP页面开头处声明taglib指令 代码如下

<%taglib prefix="form" uri="http://www.springframework.org/tags/form"%>

表单包含元素如下 

spring 中 controller相关标签 spring标签库详解_spring

 数据绑定

1：创建ch2_4应用并导入相关的JAR包

2：创建Web和Spring MVC配置类

在src目录下创建名为config的包 并创建WebConfig和SpringMVCConfig配置类

Webconfig代码如下

package config;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import org.springframework.web.WebApplicationInitializer;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.servlet.DispatcherServlet;
public class WebConfig implements WebApplicationInitializer{
	@Override
	public void onStartup(ServletContext arg0) throws ServletException {
		AnnotationConfigWebApplicationContext ctx 
		= new AnnotationConfigWebApplicationContext();
		ctx.register(SpringMVCConfig.class);//注册Spring MVC的Java配置类SpringMVCConfig
		ctx.setServletContext(arg0);//和当前ServletContext关联
		/**
		 * 注册Spring MVC的DispatcherServlet
		 */
		javax.servlet.ServletRegistration.Dynamic servlet =
				arg0.addServlet("dispatcher", new DispatcherServlet(ctx));
		servlet.addMapping("/");
		servlet.setLoadOnStartup(1);
		/**
		 * 注册字符编码过滤器
		 */
		javax.servlet.FilterRegistration.Dynamic filter =
				arg0.addFilter("characterEncodingFilter", CharacterEncodingFilter.class);
		filter.setInitParameter("encoding", "UTF-8");
		filter.addMappingForUrlPatterns(null, false, "/*");
	}
}

SpringMVCConfig代码如下

package config;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
@Configuration
@EnableWebMvc
@ComponentScan(basePackages = {"controller","service"})
public class SpringMVCConfig implements WebMvcConfigurer {
	/**
	 * 配置视图解析器
	 */
	@Bean
	public InternalResourceViewResolver getViewResolver() {
		InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();
		viewResolver.setPrefix("/WEB-INF/jsp/");
		viewResolver.setSuffix(".jsp");
		return viewResolver;
	}
	/**
	 * 配置静态资源
	 */
	@Override
	public void addResourceHandlers(ResourceHandlerRegistry registry) {
		registry.addResourceHandler("/html/**").addResourceLocations("/html/");
		//addResourceHandler指的是对外暴露的访问路径
		//addResourceLocations指的是静态资源存放的位置
	}
}

3：创建View层

包含两个JSP页面 一个是信息输入页面userAdd.jsp 一个是信息显示页面userList.jsp

userAdd.jsp代码如下

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<form:form modelAttribute="user"  method="post" action=" ${pageContext.request.contextPath }/user/save">
    <fieldset>
        <legend>添加一个用户</legend>
        <p>
            <label>用户名:</label>
            <form:input path="userName"/>
        </p>
        <p>
            <label>爱好:</label>
            <form:checkboxes items="${hobbys}"  path="hobby" />
        </p>
        <p>
            <label>朋友:</label>
            <form:checkbox path="friends" value="张三"/>张三
            <form:checkbox path="friends" value="李四"/>李四
            <form:checkbox path="friends" value="王五"/>王五
            <form:checkbox path="friends" value="赵六"/>赵六
        </p>
        <p>
            <label>职业:</label>
            <form:select path="carrer"> 
                <option/>请选择职业
                <form:options items="${carrers }"/>
            </form:select>
        </p>
        <p>
            <label>户籍:</label>
            <form:select path="houseRegister">
                <option/>请选择户籍
                <form:options items="${houseRegisters }"/>
            </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>

userList.jsp代码如下

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
    <h1>用户列表</h1>
    <a href="<c:url value="${pageContext.request.contextPath }/user/input"/>">继续添加</a>
    <table>
        <tr>
            <th>用户名</th>
            <th>兴趣爱好</th>
            <th>朋友</th>
            <th>职业</th>
            <th>户籍</th>
            <th>个人描述</th>
        </tr>
        <!-- JSTL标签，请参考本书的相关内容 -->
        <c:forEach items="${users}" var="user">
            <tr>
                <td>${user.userName }</td>
                <td>
                	<c:forEach items="${user.hobby }" var="hobby">
                		${hobby } 
                	</c:forEach>
                </td>
                <td>
                	<c:forEach items="${user.friends }" var="friend">
                		${friend } 
                	</c:forEach>
                </td>
                <td>${user.carrer }</td>
                <td>${user.houseRegister }</td>
                <td>${user.remark }</td>
            </tr>
        </c:forEach>
    </table>
</body>
</html>

4：创建领域模型

在src目录下创建pojo包 并创建User类

package pojo;

public class User {
	private String userName;
	private String[] hobby;//兴趣爱好
	private String[] friends;//朋友
	private String carrer;
	private String houseRegister;
	private String remark;
	public String getUserName() {
		return userName;
	}
	public void setUserName(String userName) {
		this.userName = userName;
	}
	public String[] getHobby() {
		return hobby;
	}
	public void setHobby(String[] hobby) {
		this.hobby = hobby;
	}
	public String[] getFriends() {
		return friends;
	}
	public void setFriends(String[] friends) {
		this.friends = friends;
	}
	public String getCarrer() {
		return carrer;
	}
	public void setCarrer(String carrer) {
		this.carrer = carrer;
	}
	public String getHouseRegister() {
		return houseRegister;
	}
	public void setHouseRegister(String houseRegister) {
		this.houseRegister = houseRegister;
	}
	public String getRemark() {
		return remark;
	}
	public void setRemark(String remark) {
		this.remark = remark;
	}
}

5：创建Service层

Service层使用静态集合变量users模拟数据库存储用户信息，包括添加用户和查询用户两个功能

UserService接口类代码如下

package service;
import java.util.ArrayList;
import pojo.User;
public interface UserService {
	boolean addUser(User u);
	ArrayList<User> getUsers();
}

UserServiceImpl实现类代码如下

package service;
import java.util.ArrayList;
import org.springframework.stereotype.Service;
import pojo.User;
@Service
public class UserServiceImpl implements UserService{
	//使用静态集合变量users模拟数据库
	private static ArrayList<User> users = new ArrayList<User>();
	@Override
	public boolean addUser(User u) {
		if(!"IT民工".equals(u.getCarrer())){//不允许添加IT民工
			users.add(u);
			return true;
		}
		return false;
	}
	@Override
	public ArrayList<User> getUsers() {
		return users;
	}
}

6：创建Controller层

在Controller类的UserController中定义了请求处理方法 代码如下

package controller;
import java.util.HashMap;
import java.util.List;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import pojo.User;
import service.UserService;
@Controller
@RequestMapping("/user")
public class UserController {
	// 得到一个用来记录日志的对象，这样打印信息的时候能够标记打印的是那个类的信息
	private static final Log logger = LogFactory.getLog(UserController.class);
	@Autowired
	private UserService userService;
	@RequestMapping(value = "/input")
	public String inputUser(Model model) {
		HashMap<String, String> hobbys = new HashMap<String, String>();
		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");
	     // 如果model中没有user属性，userAdd.jsp会抛出异常，因为表单标签无法找到
// 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", "coding搬运工", "IT民工", "其它" });
		model.addAttribute("houseRegisters", new String[] { "北京", "上海", "广州", "深圳", "其它" });
		return "userAdd";
	}
	@RequestMapping(value = "/save")
	public String addUser(@ModelAttribute User user, Model model) {
		if (userService.addUser(user)) {
			logger.info("成功");
			return "redirect:/user/list";
		} else {
			logger.info("失败");
			HashMap<String, String> hobbys = new HashMap<String, String>();
			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");
			// 这里不需要model.addAttribute("user", new
			// User())，因为@ModelAttribute指定form backing object
			model.addAttribute("hobbys", hobbys);
	model.addAttribute("carrers", new String[] { "教师", "学生", "coding搬运工", "IT民工", "其它" });
		model.addAttribute("houseRegisters", new String[] { "北京", "上海", "广州", "深圳", "其它" });
			return "userAdd";
		}
	}
	@RequestMapping(value = "/list")
	public String listUsers(Model model) {
		List<User> users = userService.getUsers();
		model.addAttribute("users", users);
		return "userList";
	}
}

7：测试应用 启动主类后 通过地址

http://localhost:8080/ch2_4/user/input测试应用接口

 测试效果如下

 

spring 中 controller相关标签 spring标签库详解_mvc_02