Introduction to the "Comment" framework library commonly used in the Java class library

There are many commonly used "annotation" framework libraries in the Java class library. This article will introduce several common annotation framework libraries and provide related Java code examples. 1. Spring framework Spring is a popular Java development framework, which provides rich annotations to simplify development.The most commonly used annotations are@Component,@AutoWired and @RestController. @Component annotations are used to mark a component in a class in Spring container, which is convenient for use by automatic assembly.The example code is as follows: @Component public class MyComponent { // class implementation } @Autowired annotation is used to automatically assemble bean in the Spring container.The example code is as follows: @Component public class MyClass { @Autowired private MyComponent myComponent; // class implementation } @RestController's annotation is used to declare a controller with a class of Restful API, which will automatically handle HTTP requests and responses.The example code is as follows: @RestController public class MyController { @GetMapping("/hello") public String hello() { return "Hello, World!"; } } 2. Hibernate framework Hibernate is an object relationship mapping (ORM) framework, which simplifies the mapping between the Java object and the database.Hibernate provides a series of annotations, such as@Entity,@Column and @ID. @Entity annotation is used to mark a Java class as an entity in the database table.The example code is as follows: @Entity public class User { @Id private Long id; @Column private String name; // getter and setter methods } @Column annotation is used to mark a class member variable and the columns in the database table.The example code is as follows: @Entity public class User { @Id private Long id; @Column(name = "user_name") private String name; // getter and setter methods } @Id annotation is used to specify the attributes of the physical class as the main key.The example code is as follows: @Entity public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column private String name; // getter and setter methods } 3. Jackson framework Jackson is a popular Java JSON processing library that provides a series of annotations for serialization and derivative operation.The most commonly used annotations are@jsonserialize,@jsondeserialize and @jsonproperty. @Jsonserialize annotations are used to specify the custom serializer, converting the Java object into a JSON format.The example code is as follows: public class MySerializer extends JsonSerializer<MyClass> { @Override public void serialize(MyClass value, JsonGenerator gen, SerializerProvider serializers) throws IOException { // custom serialization logic } } @JsonSerialize(using = MySerializer.class) public class MyClass { // class implementation } @JSONDESERIALIZE annotations are used to specify the customized derializer and convert the JSON format into a Java object.The example code is as follows: public class MyDeserializer extends JsonDeserializer<MyClass> { @Override public MyClass deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException { // custom deserialization logic } } @JsonDeserialize(using = MyDeserializer.class) public class MyClass { // class implementation } @Jsonproperty annotations are used to specify the mapping relationship between Java object attributes and JSON fields.The example code is as follows: public class MyClass { @JsonProperty("username") private String name; // getter and setter methods } Summarize: This article introduces several common Java annotation framework libraries, including Spring, Hibernate and Jackson.These framework libraries provide rich annotations that can help developers simplify the development process, accelerate development speed, and improve the readability and maintenance of code.