我想学习 JAXB，但我的示例 xml 文件有问题。 xml:
<?xml version="1.0"?>
<catalog>
<books>
<book id="bk101">
<author>Gambardella, Matthew</author>
<title>XML Developer's Guide</title>
<genre>Computer</genre>
<price>44.95</price>
<publish_date>2000-10-01</publish_date>
<description>An in-depth look at creating applications
with XML.</description>
</book>
<book id="bk102">
<author>Ralls, Kim</author>
<title>Midnight Rain</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2000-12-16</publish_date>
<description>A former architect battles corporate zombies,
an evil sorceress, and her own childhood to become queen
of the world.</description>
</book>
<book id="bk103">
<author>Corets, Eva</author>
<title>Maeve Ascendant</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2000-11-17</publish_date>
<description>After the collapse of a nanotechnology
society in England, the young survivors lay the
foundation for a new society.</description>
</book>
<book id="bk104">
<author>Corets, Eva</author>
<title>Oberon's Legacy</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2001-03-10</publish_date>
<description>In post-apocalypse England, the mysterious
agent known only as Oberon helps to create a new life
for the inhabitants of London. Sequel to Maeve
Ascendant.</description>
</book>
<book id="bk105">
<author>Corets, Eva</author>
<title>The Sundered Grail</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2001-09-10</publish_date>
<description>The two daughters of Maeve, half-sisters,
battle one another for control of England. Sequel to
Oberon's Legacy.</description>
</book>
<book id="bk106">
<author>Randall, Cynthia</author>
<title>Lover Birds</title>
<genre>Romance</genre>
<price>4.95</price>
<publish_date>2000-09-02</publish_date>
<description>When Carla meets Paul at an ornithology
conference, tempers fly as feathers get ruffled.</description>
</book>
<book id="bk107">
<author>Thurman, Paula</author>
<title>Splish Splash</title>
<genre>Romance</genre>
<price>4.95</price>
<publish_date>2000-11-02</publish_date>
<description>A deep sea diver finds true love twenty
thousand leagues beneath the sea.</description>
</book>
<book id="bk108">
<author>Knorr, Stefan</author>
<title>Creepy Crawlies</title>
<genre>Horror</genre>
<price>4.95</price>
<publish_date>2000-12-06</publish_date>
<description>An anthology of horror stories about roaches,
centipedes, scorpions and other insects.</description>
</book>
<book id="bk109">
<author>Kress, Peter</author>
<title>Paradox Lost</title>
<genre>Science Fiction</genre>
<price>6.95</price>
<publish_date>2000-11-02</publish_date>
<description>After an inadvertant trip through a Heisenberg
Uncertainty Device, James Salway discovers the problems
of being quantum.</description>
</book>
<book id="bk110">
<author>O'Brien, Tim</author>
<title>Microsoft .NET: The Programming Bible</title>
<genre>Computer</genre>
<price>36.95</price>
<publish_date>2000-12-09</publish_date>
<description>Microsoft's .NET initiative is explored in
detail in this deep programmer's reference.</description>
</book>
<book id="bk111">
<author>O'Brien, Tim</author>
<title>MSXML3: A Comprehensive Guide</title>
<genre>Computer</genre>
<price>36.95</price>
<publish_date>2000-12-01</publish_date>
<description>The Microsoft MSXML3 parser is covered in
detail, with attention to XML DOM interfaces, XSLT processing,
SAX and more.</description>
</book>
<book id="bk112">
<author>Galos, Mike</author>
<title>Visual Studio 7: A Comprehensive Guide</title>
<genre>Computer</genre>
<price>49.95</price>
<publish_date>2001-04-16</publish_date>
<description>Microsoft Visual Studio 7 is explored in depth,
looking at how Visual Basic, Visual C++, C#, and ASP+ are
integrated into a comprehensive development
environment.</description>
</book>
</books>
<movies>
<movie id="m101">
<author>George Lucas</author>
<title>Star Wars</title>
<genre>Science Fiction</genre>
<price>32.95</price>
</movie>
<movie id="m202">
<author>Francis Ford Coppola</author>
<title>The Godfather</title>
<genre>Drama</genre>
<price>36.95</price>
</movie>
</movies>
</catalog
这是我的代码，它不起作用。 主要:
public class Main {
public static void main(String[] args) throws Exception {
Scanner scanner = new Scanner(System.in);
System.out.println("Path: ");
String filePath = scanner.next();
JAXBContext jaxbContext = JAXBContext.newInstance(Catalog.class);
Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
Catalog catalog = (Catalog) unmarshaller.unmarshal(new File(filePath));
// test
System.out.println("All titles in uploaded catalog: ");
for (int b = 0; b<catalog.getBooks().getBookList().size(); b++) {
catalog.getBooks().getBookList().get(b).getTitle();
catalog.getBooks().getBookList().get(b).getPrice();
}
for (int m = 0; m<catalog.getMovies().getMovieList().size(); m++) {
catalog.getMovies().getMovieList().get(m).getTitle();
catalog.getMovies().getMovieList().get(m).getPrice();
}
}
}
书:
为简洁起见，省略 电影:
为简洁起见，省略 书籍:
@XmlRootElement(name = "books")
public class Books {
private List<Book> bookList = new ArrayList<>();
@XmlElements(@XmlElement(name = "books"))
public List<Book> getBookList() {
return bookList;
}
public void setBookList(List<Book> bookList) {
this.bookList = bookList;
}
}
电影:
@XmlRootElement(name = "movies")
public class Movies {
private List<Movie> movieList = new ArrayList<>();
@XmlElements(@XmlElement(name = "movies"))
public List<Movie> getMovieList() {
return movieList;
}
public void setMovieList(List<Movie> movieList) {
this.movieList = movieList;
}
}
目录:
@XmlRootElement(name = "catalog")
public class Catalog {
private Books books = new Books();
private Movies movies = new Movies();
//@XmlElements(@XmlElement(name = "books"))
public Books getBooks() {
return books;
}
public void setBooks(Books books) {
this.books = books;
}
//@XmlElements(@XmlElement(name = "movies"))
public Movies getMovies() {
return movies;
}
public void setMovies(Movies movies) {
this.movies = movies;
}
}
我认为 Catalog 类中可能存在一些错误，但我不知道如何修改它，而且我尝试将其转换为 xsd 并使用 xcj 生成类，但实际上 xcj 无法在我的操作系统上运行。感谢您的关注。
最佳答案
您实际上可以删除中间的 Books 或 Movies 类，您不需要它们。这是使用 @XmlElementWrapper 的版本:
public class Catalog {
@XmlElementWrapper(name="books")
@XmlElement(name="book")
public List<Book> books;
}
public class Book {
@XmlAttribute
public String id;
public String author;
public String title;
public String genre;
public BigDecimal price;
@XmlElement(name="publish_date")
public XMLGregorianCalendar publishDate;
public String description;
}
测试:
@Test
public void unmarshallsCatalog() throws JAXBException, IOException {
JAXBContext context = JAXBContext.newInstance(Catalog.class);
Unmarshaller unmarshaller = context.createUnmarshaller();
try (InputStream is = Thread.currentThread()
.getContextClassLoader()
.getResourceAsStream("catalog.xml")) {
Catalog catalog = unmarshaller.unmarshal(new StreamSource(is), Catalog.class).getValue();
Assert.assertEquals(catalog.books.size(), 12);
}
}
以下内容也对我有用:
public class Catalog {
public Books books;
}
public class Books {
@XmlElement(name = "book")
public List<Book> bookList;
}
我认为您的错误可能是在 Books 类中:
@XmlElements(@XmlElement(name = "books"))
public List<Book> getBookList() {
return bookList;
}
您必须映射 book 元素，而不是 books 元素。
此外，像 @XmlElements(@XmlElement(name = "books")) 这样的注释也不会执行您可能认为的操作。它不映射书籍列表。对于一个元素来说，它甚至没有意义。
@XmlElements 可用于将不同元素映射到一个属性。假设您有一个类似以下的 XML:
马修·甘巴德拉 XML 开发人员指南 电脑 44.95 2000年10月1日 深入了解创建应用程序 使用 XML。 乔治·卢卡斯 星球大战 科幻小说 32.95
基本上，书籍和电影混合在一个目录中。 Book 和 Movie 可以实现相同的接口(interface) Item。在这种情况下，您可能希望将元素 book 和 movie 映射到同一属性 items。您可以这样做:
@XmlElements({
@XmlElement(name="book", type=Book.class),
@XmlElement(name="movie", type=Movie.class)
})
public List<? extends Item> items;
根据元素名称，JAXB 将解码 Book 或 Movie 并将它们添加到 items 列表中。
关于 java |如何使用 JAXB 解析此 ('3-level' ) xml？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/49767013/