Jackson DataFormat YAML advanced application based on the Java class library
Jackson DataFormat YAML advanced application based on the Java class library
Overview:
Jackson DataFormat Yaml is a class library based on Java, which is used to process data in YAML (Yaml Ain'T Markup Language) format.In this article, we will explore the advanced applications of Jackson DataFormat Yaml and provide some Java code examples to help readers better understand and use this type of library.
Table of contents:
1. What is Jackson DataFormat yaml?
2. Import jackson datafulmat yaml
3. Basic YAML reading and writing operation
4. Serialization of complex data structure
5. Custom YAML mapping rules
6. Use Jackson DataFormat YAML to process YAML files
7. Summary
1. What is Jackson DataFormat yaml?
Jackson DataFormat Yaml is an extension of the Jackson library to process data in YAML format.It provides a simple way to serialize the text of the Java object in YAML format, and sequences the text of the YAML format into a Java object.This expansion library makes it easy to process YAML data.
2. Import jackson datafulmat yaml
First of all, we need to import the Jackson DataFormat Yaml library and its dependencies.In the Maven project, we can import it in the pom.xml file in the following way:
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-yaml</artifactId>
<version>2.12.3</version>
</dependency>
3. Basic YAML reading and writing operation
First of all, we need to create a YAML file to demonstrate the reading and writing operation.Suppose we have a file called `Person.yaml`, and the content is as follows:
yaml
name: John
age: 30
Now, we will show how to read and write this Yaml file with Jackson DataFormat Yaml library.
First, we need to create a class to represent the data model of Person:
public class Person {
private String name;
private int age;
// Define the appropriate constructor, Getter, and Setter method here
}
Next, we can use the following code to read the yaml file as the Java object:
public class Main {
public static void main(String[] args) throws IOException {
ObjectMapper objectMapper = new ObjectMapper(new YAMLFactory());
Person person = objectMapper.readValue(new File("person.yaml"), Person.class);
System.out.println (Person.getName ()); // Output: John
System.out.println (Person.getage ()); // Output: 30
}
}
Now, we show how to write Java objects into YAML files:
public class Main {
public static void main(String[] args) throws IOException {
ObjectMapper objectMapper = new ObjectMapper(new YAMLFactory());
Person person = new Person("John", 30);
objectMapper.writeValue(new File("person.yaml"), person);
}
}
4. Serialization of complex data structure
In addition to basic types and simple objects, Jackson DataFormat Yaml can also process complex data structures, such as lists and nested objects.Let's take a look at how to perform such serialization and derivativeization.
First of all, consider the following YAML file, which contains a list of multiple personnel information:
yaml
persons:
- name: John
age: 30
- name: Alice
age: 25
We can create the following categories to represent these data structures:
public class PersonList {
private List<Person> persons;
// Define the appropriate constructor, Getter, and Setter method here
}
Now, let us show how to turn the yaml files into a PersonList object that contains multiple person:
public class Main {
public static void main(String[] args) throws IOException {
ObjectMapper objectMapper = new ObjectMapper(new YAMLFactory());
PersonList personList = objectMapper.readValue(new File("persons.yaml"), PersonList.class);
for (Person person : personList.getPersons()) {
System.out.println (Person.getName ()); // Output: John, Alice
System.out.println (Person.getage ()); // Output: 30, 25
}
}
}
Similarly, we can also sequence the PersonList object that contains multiple person to YAML files:
public class Main {
public static void main(String[] args) throws IOException {
ObjectMapper objectMapper = new ObjectMapper(new YAMLFactory());
List<Person> persons = new ArrayList<>();
persons.add(new Person("John", 30));
persons.add(new Person("Alice", 25));
PersonList personList = new PersonList(persons);
objectMapper.writeValue(new File("persons.yaml"), personList);
}
}
5. Custom YAML mapping rules
Jackson DataFormat Yaml also allows us to customize the mapping rules between YAML data and Java objects.We can use the correspondence between the YAML field and the Java member variables with `@jsonproperty` and other Jackson annotations.
For example, suppose we have a yaml file as follows:
yaml
person:
full-name: John Doe
date-of-birth: 1990-01-01
We can use the following code to turn their deepertdles into a Person object:
public class Person {
@JsonProperty("full-name")
private String fullName;
@JsonProperty("date-of-birth")
private LocalDate dateOfBirth;
// Define the appropriate constructor, Getter, and Setter method here
}
Now, let us show how to turn from a Person object sequence to a YAML file with a custom field name:
public class Main {
public static void main(String[] args) throws IOException {
ObjectMapper objectMapper = new ObjectMapper(new YAMLFactory());
Person person = new Person("John Doe", LocalDate.parse("1990-01-01"));
objectMapper.writeValue(new File("person.yaml"), person);
}
}
6. Use Jackson DataFormat YAML to process YAML files
In addition to reading and writing YAML data, Jackson DataFormat Yaml also provides the function of processing the entire YAML file.We can use the `yamlnode` object to represent a yaml file and perform various operations, such as finding, modification and deleting nodes.The following is an example code:
public class Main {
public static void main(String[] args) throws IOException {
ObjectMapper objectMapper = new ObjectMapper(new YAMLFactory());
File yamlFile = new File("person.yaml");
JsonNode yamlNode = objectMapper.readTree(yamlFile);
// Find a specific node
String fullName = yamlNode.get("person").get("full-name").asText();
System.out.println (fullName); // Output: John Doe
// Modify the node
((ObjectNode) yamlNode).put("person", "New Name");
// Delete nodes
((ObjectNode) yamlNode).remove("person");
// Write the modified node back to the Yaml file
objectMapper.writerWithDefaultPrettyPrinter().writeValue(yamlFile, yamlNode);
}
}
7. Summary
In this article, we introduced the basic usage and advanced application of the Jackson DataFormat Yaml library.We have learned how to read and write Yaml files, how to process complex data structures, and how to customize the YAML mapping rules.We also show how to use Jackson DataFormat Yaml to process the entire YAML file and perform node operations.I hope this article can help you better understand and apply Jackson DataFormat Yaml.
