How Java uses Jackson serialization and deserialization
Jackson is a fast JSON processing library for Java that can handle the conversion between JSON data and Java objects. It provides flexible ways to serialize and deserialize objects, supports multiple data binding methods (such as POJO, Map, List, etc.), and supports customization of serialization and deserialization details through annotations.
Jackson mainly includes the following key classes and methods:
1. Object Mapper: The Object Mapper class is Jackson's core class used to serialize and deserialize objects. It provides a series of methods to handle the conversion between Java objects and JSON.
2. readValue(): The readValue() method is used to deserialize JSON data into Java objects. Can accept input from different data sources, such as strings, byte arrays, files, etc.
3. writeValue(): The writeValue() method is used to serialize Java objects into JSON data. It can be output to different targets, such as strings, byte arrays, files, etc.
4. Object Mapper Configuration: Using Object Mapper, multiple serialization and deserialization options can be configured, such as setting date format and whether to indent output.
The following is a Java example code for serialization and deserialization using Jackson:
//Import Jackson's dependency package (requires adding a dependency on Jackson databind)
//Maven Dependency:
// <dependency>
// <groupId>com.fasterxml.jackson.core</groupId>
// <artifactId>jackson-databind</artifactId>
// <version>2.12.4</version>
// </dependency>
import com.fasterxml.jackson.databind.ObjectMapper;
public class JacksonExample {
public static void main(String[] args) throws Exception {
//Create an Object Mapper object
ObjectMapper objectMapper = new ObjectMapper();
//Convert Java objects to JSON strings (serialization)
Person person = new Person("John", 30);
String json = objectMapper.writeValueAsString(person);
System.out.println("Serialized JSON: " + json);
//Convert JSON strings to Java objects (deserialize)
Person deserializedPerson = objectMapper.readValue(json, Person.class);
System.out.println("Deserialized Person: " + deserializedPerson);
}
//Define a POJO class
static class Person {
private String name;
private int age;
public Person(String name, int age) {
this.name = name;
this.age = age;
}
//Must have an parameterless construction method for creating objects during deserialization
public Person() {
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Person{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
}
}
The above code demonstrates Jackson's serialization and deserialization functions in the most basic way. Convert the Java object 'Person' to a JSON string, and then convert the JSON string to a Java object. In this example, we used the 'writeValueAsString()' method of 'Object Mapper' for serialization and the 'readValue()' method for deserialization.
In actual development, more complex operations such as Type conversion, custom serialization and deserialization may be required, which can be realized by using the annotation and configuration methods provided by Jackson.
