19.3 数据绑定范例

在表单标签库中利用标签进行数据绑定的例子，见app19a 应用程序。这个范例围绕着domain类Book进行。这个类中有几个属性，包括一个类型为Category的category属性。Category有id和name两个属性。
这个应用程序允许列出书目、添加新书，以及编辑书目。

19.3.1 目录结构

下面是app19a的目录结构。

E:\workspace_web\app19a
├─pom.xml
├─src
│ ├─main
│ │ ├─java
│ │ │ └─app19a
│ │ │   ├─controller
│ │ │   │ └─BookController.java
│ │ │   ├─domain
│ │ │   │ ├─Book.java
│ │ │   │ └─Category.java
│ │ │   └─service
│ │ │     ├─BookService.java
│ │ │     └─BookServiceImpl.java
│ │ └─resources
│ └─test
│   └─java
└─WebContent
  ├─css
  │ └─main.css
  ├─META-INF
  │ └─MANIFEST.MF
  └─WEB-INF
    ├─config
    │ └─springmvc-config.xml
    ├─jsp
    │ ├─BookAddForm.jsp
    │ ├─BookEditForm.jsp
    │ └─BookList.jsp
    ├─lib
    └─web.xml

19.3.2Domain类

Book类和Category类是这个应用程序中的domain类，它们分别如清单19.1和清单19.2所示。

清单19.1Book类

package app19a.domain;
import java.io.Serializable;
public class Book
    implements
        Serializable
{
    private static final long serialVersionUID 
            = 1520961851058396786L;
    private long id;
    private String isbn;
    private String title;
    private Category category;
    private String author;
    public Book()
    {}
    public Book(long id,String isbn,String title,
                Category category,String author)
    {
        this.id = id;
        this.isbn = isbn;
        this.title = title;
        this.category = category;
        this.author = author;
    }
    public long getId()
    {
        return id;
    }
    public void setId(long id)
    {
        this.id = id;
    }
    public String getIsbn()
    {
        return isbn;
    }
    public void setIsbn(String isbn)
    {
        this.isbn = isbn;
    }
    public String getTitle()
    {
        return title;
    }
    public void setTitle(String title)
    {
        this.title = title;
    }
    public Category getCategory()
    {
        return category;
    }
    public void setCategory(Category category)
    {
        this.category = category;
    }
    public String getAuthor()
    {
        return author;
    }
    public void setAuthor(String author)
    {
        this.author = author;
    }
}

Category类

package app19a.domain;
import java.io.Serializable;
public class Category
    implements
        Serializable
{
    private static final long serialVersionUID 
        = 5658716793957904104L;
    private int id;
    private String name;
    public Category()
    {}
    public Category(int id,String name)
    {
        this.id = id;
        this.name = name;
    }
    public int getId()
    {
        return id;
    }
    public void setId(int id)
    {
        this.id = id;
    }
    public String getName()
    {
        return name;
    }
    public void setName(String name)
    {
        this.name = name;
    }
}

19.3.3Controller类

下面的范例为Book提供了一个controller：BookController类。它允许用户创建新书目、更新书的详细信息，并在系统中列出所有书目。清单19.3中展示了BookController类。

BookController类

package app19a.controller;
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.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import app19a.domain.Book;
import app19a.domain.Category;
import app19a.service.BookService;
@Controller
public class BookController
{
    @Autowired
    private BookService bookService;
    private static final Log logger = LogFactory
        .getLog(BookController.class);
    @RequestMapping(value = "/book_input")
    public String inputBook(Model model)
    {
        List<Category> categories = 
              bookService.getAllCategories();
        model.addAttribute("categories", categories);
        model.addAttribute("book", new Book());
        return "BookAddForm";
    }
    @RequestMapping(value = "/book_edit/{id}")
    public String editBook(Model model,@PathVariable
    long id)
    {
        List<Category> categories =
            bookService.getAllCategories();
        model.addAttribute("categories", categories);
        Book book = bookService.get(id);
        model.addAttribute("book", book);
        return "BookEditForm";
    }
    @RequestMapping(value = "/book_save")
    public String saveBook(@ModelAttribute
    Book book)
    {
        Category category = bookService
            .getCategory(book.getCategory().getId());
        book.setCategory(category);
        bookService.save(book);
        return "redirect:/book_list";
    }
    @RequestMapping(value = "/book_update")
    public String updateBook(@ModelAttribute
    Book book)
    {
        Category category = bookService
            .getCategory(book.getCategory().getId());
        book.setCategory(category);
        bookService.update(book);
        return "redirect:/book_list";
    }
    @RequestMapping(value = "/book_list")
    public String listBooks(Model model)
    {
        logger.info("book_list");
        List<Book> books = bookService.getAllBooks();
        model.addAttribute("books", books);
        return "BookList";
    }
}

BookController依赖BookService进行一些后台处理。@Autowired注解用于给BookController注入一个BookService实现：

@Autowired
private BookService bookService;

19.3.4 Service类

清单19.4和清单19.5分别展示了BookService接口和BookServiceImpl类。顾名思义，BookServiceImpl就是实现BookService。

BookService接口

package app19a.service;
import java.util.List;
import app19a.domain.Book;
import app19a.domain.Category;
public interface BookService
{
    List<Category> getAllCategories();
    Category getCategory(int id);
    List<Book> getAllBooks();
    Book save(Book book);
    Book update(Book book);
    Book get(long id);
    long getNextId();
}

BookServiceImpl类

package app19a.service;
import java.util.ArrayList;
import java.util.List;
import org.springframework.stereotype.Service;
import app19a.domain.Book;
import app19a.domain.Category;
@Service
public class BookServiceImpl
    implements
        BookService
{
    /*
     * this implementation is not thread-safe
     */
    private List<Category> categories;
    private List<Book> books;
    public BookServiceImpl()
    {
        categories = new ArrayList<Category>();
        Category category1 = new Category(1, "Computing");
        Category category2 = new Category(2, "Travel");
        Category category3 = new Category(3, "Health");
        categories.add(category1);
        categories.add(category2);
        categories.add(category3);
        books = new ArrayList<Book>();
        books.add(new Book(1L, "9780980839623",
            "Servlet & JSP: A Tutorial",
            category1, "Budi Kurniawan"));
        books.add(new Book(2L, "9780980839630",
            "C#: A Beginner's Tutorial",
            category1, "Jayden Ky"));
    }
    @Override
    public List<Category> getAllCategories()
    {
        return categories;
    }
    @Override
    public Category getCategory(int id)
    {
        for(Category category: categories)
        {
            if(id == category.getId())
            {
                return category;
            }
        }
        return null;
    }
    @Override
    public List<Book> getAllBooks()
    {
        return books;
    }
    @Override
    public Book save(Book book)
    {
        book.setId(getNextId());
        books.add(book);
        return book;
    }
    @Override
    public Book get(long id)
    {
        for(Book book: books)
        {
            if(id == book.getId())
            {
                return book;
            }
        }
        return null;
    }
    @Override
    public Book update(Book book)
    {
        int bookCount = books.size();
        for(int i = 0;i < bookCount;i++)
        {
            Book savedBook = books.get(i);
            if(savedBook.getId() == book.getId())
            {
                books.set(i, book);
                return book;
            }
        }
        return book;
    }
    @Override
    public long getNextId()
    {
        // needs to be locked
        long id = 0L;
        for(Book book: books)
        {
            long bookId = book.getId();
            if(bookId > id)
            {
                id = bookId;
            }
        }
        return id + 1;
    }
}

BookServiceImpl类中包含了一个Book对象的List和一个Category对象的List。这两个List都是在实例化类时生成的。这个类中还包含了获取所有书目、获取单个书目以及添加和更新书目的方法。

19.3.5 配置文件

清单19.6展示了app19a中的Spring MVC配置文件。

SpringMVC配置文件

<?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:mvc="http://www.springframework.org/schema/mvc"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd     
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-4.3.xsd">
    <!-- 扫描控制器 -->
    <context:component-scan
        base-package="app19a.controller" />
    <!-- 扫描服务类 -->
    <context:component-scan
        base-package="app19a.service" />
    <mvc:annotation-driven />
    <mvc:resources mapping="/css/**" location="/css/" />
    <mvc:resources mapping="/*.html" location="/" />
    <!-- 视图解析器 -->
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/" />
        <property name="suffix" value=".jsp" />
    </bean>
</beans>

component-scan bean使得app19a.controller包和app19a.service包得以扫描。

19.3.6 视图

app19a中使用的3个JSP页面如清单19.7、清单19.8和清单19.9所示。BookAddForm.jsp和BookEditForm.jsp页面中使用的是来自表单标签库的标签。

清单19.7 BookList.jsp页面

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML>
<html>
<head>
<title>Book List</title>
<style type="text/css">
@import url("<c:url value="/css/main.css"/>");
</style>
</head>
<body>
    <div id="global">
        <h1>Book List</h1>
        <a href="<c:url value="/book_input"/>">Add Book</a>
        <table>
            <tr>
                <th>Category</th>
                <th>Title</th>
                <th>ISBN</th>
                <th>Author</th>
                <th>&nbsp;</th>
            </tr>
            <c:forEach items="${books}" var="book">
                <tr>
                    <td>${book.category.name}</td>
                    <td>${book.title}</td>
                    <td>${book.isbn}</td>
                    <td>${book.author}</td>
                    <td><a href="book_edit/${book.id}">Edit</a></td>
                </tr>
            </c:forEach>
        </table>
    </div>
</body>
</html>

清单19.8 BookAddForm.jsp页面

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML>
<html>
<head>
<title>Add Book Form</title>
<style type="text/css">
@import url("<c:url value="/css/main.css"/>");
</style>
</head>
<body>
    <div id="global">
        <!--     SpringMVC表单标签 -->
        <form:form commandName="book" action="book_save" method="post">
            <fieldset>
                <legend>Add a book</legend>
                <p>
                    <label for="category">Category: </label>
                    <form:select id="category" path="category.id"
                        items="${categories}" itemLabel="name"
                        itemValue="id" />
                </p>
                <p>
                    <label for="title">Title: </label>
                    <form:input id="title" path="title" />
                </p>
                <p>
                    <label for="author">Author: </label>
                    <form:input id="author" path="author" />
                </p>
                <p>
                    <label for="isbn">ISBN: </label>
                    <form:input id="isbn" path="isbn" />
                </p>
                <p id="buttons">
                    <input id="reset" type="reset" tabindex="4">
                    <input id="submit" type="submit" tabindex="5"
                        value="Add Book">
                </p>
            </fieldset>
        </form:form>
    </div>
</body>
</html>

清单19.9 BookEditForm.jsp页面

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE HTML>
<html>
<head>
<title>Edit Book Form</title>
<style type="text/css">
@import url("<c:url value="/css/main.css"/>");
</style>
</head>
<body>
    <div id="global">
        <form:form commandName="book" action="/book_update"
            method="post">
            <fieldset>
                <legend>Edit a book</legend>
                <form:hidden path="id" />
                <p>
                    <label for="category">Category: </label>
                    <form:select id="category" path="category.id"
                        items="${categories}" itemLabel="name"
                        itemValue="id" />
                </p>
                <p>
                    <label for="title">Title: </label>
                    <form:input id="title" path="title" />
                </p>
                <p>
                    <label for="author">Author: </label>
                    <form:input id="author" path="author" />
                </p>
                <p>
                    <label for="isbn">ISBN: </label>
                    <form:input id="isbn" path="isbn" />
                </p>
                <p id="buttons">
                    <input id="reset" type="reset" tabindex="4">
                    <input id="submit" type="submit" tabindex="5"
                        value="Update Book">
                </p>
            </fieldset>
        </form:form>
    </div>
</body>
</html>

19.3.7 测试应用

要想测试这个应用程序范例，请打开以下网页：
http://localhost:8080/app19a/book_list
图19.2所示为第一次启动这个应用程序时显示的书目列表。

单击Add Book链接添加书目，或者单击书籍详情右侧的Edit链接来编辑书目。
图19.3所示为Add Book表单。图19.4所示为EditBook表单。