Introduction to the technical principles of the Jackson DataFormat XML framework in the Java class library

Jackson is a popular Java class library for conversion between Java objects and JSON data.However, in addition to JSON, Jackson also provides a module called Jackson DataFormat XML for converting Java objects into XML formats, and reads data from XML format and maps it into the Java object. The core principle of the Jackson DataFormat XML is to specify how to convert the object into XML format and how to read the data from the XML format. First of all, we need to define the annotation in the Java object to specify how to serialize to XML.These annotations include `@jacksonxmlrootElement`, which are used to mark the names of the root element, and`@jacksonxmlproperty`, which are used to mark the name of the attributes or fields.For example, we have a Java object called `Person`: @JacksonXmlRootElement(localName = "person") public class Person { @JacksonXmlProperty(localName = "name") private String name; @JacksonXmlProperty(localName = "age") private int age; // getters and setters } In this example, we use the name of the root element to set the name of the root element to `Person`, and use the names of the attributes` name` and `Age` to use the names of the attributes` name` and `Age`. We can then use the XMLMAPPER class provided by the Jackson DataFormat XML to implement the conversion between the Java object and the XML.The following is an example of converting Java objects to XML string: Person person = new Person(); person.setName("John"); person.setAge(30); XMLMapper xmlMapper = new XmlMapper(); String xml = xmlMapper.writeValueAsString(person); System.out.println(xml); The output result will be a XML string, similar to the following: <person> <name>John</name> <age>30</age> </person> Similarly, we can also convert XML to Java objects.The following is an example of reading data from the XML string and mapped to the Java object: String xml = "<person><name>John</name><age>30</age></person>"; XMLMapper xmlMapper = new XmlMapper(); Person person = xmlMapper.readValue(xml, Person.class); System.out.println(person.getName()); // Output: John System.out.println(person.getAge()); // Output: 30 In this example, the XML string is parsed as the `Person` object using the` xmlmapper.Readvalue` method. In summary, the Jackson DataFormat XML specifies the XML format conversion rule by using the annotation of the Java object to provide a convenient way to achieve the conversion between Java objects and XML.This makes processing XML data easier and flexible, and can be seamlessly integrated with other functions of Jackson (such as JSON conversion).