Jackson DataFormat YAML parser principle and practice
Jackson DataFormat Yaml is an extension module of the Jackson library to analyze and generate data in Yaml (Yaml Ain'T Markup Language, Yaml is not a tag language) format.This article will introduce the principles of Jackson DataFormat Yaml parser and how to use its practice in Java applications.
## 1. Jackson DataFormat yaml
Jackson DataFormat Yaml provides a powerful and easy -to -use API for conversion between Java objects and YAML data.It is based on the core JSON processing library provided by Jackson, as well as the Yaml data format analysis and generation function implemented by Jackson DataFormat Yaml.
Using Jackson DataFormat Yaml can easily convert Java objects into YAML data, or convert YAML data to Java objects.This conversion process is achieved through annotations or mappingers.
## 2. Jackson DataFormat YAML parser principle
Jackson DataFormat YAML parser converts YAML data to Java objects through the following steps:
1. First, load the YAML data to the `jsonnode` object in the core library of Jackson.
2. Then, use the `ObjectMapper` object or a custom maper (Mapper) to convert the` jsonnode` object to the Java object.
Similarly, the process of converting Java objects into YAML data can be divided into two steps:
1. First, use the `ObjectMapper` object or a custom maper (Mapper) to convert the Java object to the` jsonnode` object.
2. Then, output the `jsonnode` object in yaml format.
In the process of analyzing and generating YAML data, some annotations can be used to specify the names, types, default values and other information of the field in order to more accurately control the conversion of the data.
## 3. Jackson DataFormat yaml practice
Next, we will introduce how to use Jackson DataFormat Yaml in Java applications for parsing and generating Yaml data.
First of all, you need to add Jackson DataFormat Yaml to the `POM.XML` file of the Maven project:
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-yaml</artifactId>
<version>2.12.5</version>
</dependency>
Then, you can use the following code example to demonstrate how to analyze and generate YAML data:
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
import java.io.File;
import java.io.IOException;
public class YAMLExample {
public static void main(String[] args) {
// Analyze yaml data as Java object
ObjectMapper objectMapper = new ObjectMapper(new YAMLFactory());
try {
User user = objectMapper.readValue(new File("user.yaml"), User.class);
System.out.println(user);
} catch (IOException e) {
e.printStackTrace();
}
// Generate YAML data to generate java objects
User user = new User("John Doe", 30);
try {
objectMapper.writeValue(new File("user.yaml"), user);
} catch (IOException e) {
e.printStackTrace();
}
}
}
class User {
private String name;
private int age;
// omitted by parameter constructor and Getter/Setter method
public User(String name, int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return "User{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
In the above sample code, we first created an instance of the `ObjectMapper` object and specified it as the` yamlFactory`.Then, we use the `Readvalue` method to analyze the yaml data in the` user.yaml` file as an object of the `user` and print the output.Next, we create a `user` object, and use the` writevalue` method to convert it to YAML data and write it into the `user.yaml` file.
Note that in the example code above, the `user` class needs to provide no parameter constructor and the corresponding Getter/Setter method, so that the Jackson DataFormat yaml can correctly convey the data.
## in conclusion
This article introduces the principles and practice of Jackson DataFormat Yaml parser, and how to use it in Java applications to analyze and generate YAML data.Using Jackson DataFormat Yaml, we can easily convert between Java objects and YAML data, and control the conversion process more accurately through annotations and mapper.Jackson DataFormat Yaml provides a simple and powerful way to process YAML data, making it easier and flexible to use YAML in Java applications.
