Using Jackson ​

Previously, we introduced two standard XML parsing interfaces: DOM and SAX. However, both are not very intuitive to use.

Let's examine the structure of the following XML document:

<?xml version="1.0" encoding="UTF-8" ?>
<book id="1">
    <name>Java核心技术</name>
    <author>Cay S. Horstmann</author>
    <isbn lang="CN">1234567</isbn>
    <tags>
        <tag>Java</tag>
        <tag>Network</tag>
    </tags>
    <pubDate/>
</book>

We notice that it can be easily mapped to a predefined JavaBean:

public class Book {
    public long id;
    public String name;
    public String author;
    public String isbn;
    public List<String> tags;
    public String pubDate;
}

If we can directly parse the XML document into a JavaBean, it would be much simpler than using DOM or SAX.

Fortunately, an open-source third-party library called Jackson can easily convert XML into a JavaBean. To use Jackson, add the following Maven dependency:

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-xml</artifactId>
    <version>2.10.1</version>
</dependency>

After defining the JavaBean, the XML can be parsed with just a few lines of code:

InputStream input = Main.class.getResourceAsStream("/book.xml");
JacksonXmlModule module = new JacksonXmlModule();
XmlMapper mapper = new XmlMapper(module);
Book book = mapper.readValue(input, Book.class);
System.out.println(book.id);
System.out.println(book.name);
System.out.println(book.author);
System.out.println(book.isbn);
System.out.println(book.tags);
System.out.println(book.pubDate);

Notice that XmlMapper is the core object that we need to create. It can use readValue(InputStream, Class) to read the XML and return a JavaBean directly. Running the above code, we can easily access the data from the Book object:

1
Core Java
Cay S. Horstmann
1234567
[Java, Network]
null

If the data format to be parsed is not one of Jackson's built-in standard formats, a custom parser can be configured to tell Jackson how to parse it. For more details, you can refer to the Jackson official documentation.

Exercise ​

Use Jackson to parse XML.

Summary ​

Using Jackson to parse XML allows you to directly convert XML into a JavaBean, making it very convenient.