Jackson类注解@JsonNaming的命名策略动态获取与内省

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.PropertyNamingStrategy;
import com.fasterxml.jackson.databind.cfg.SerializationConfig;
import com.fasterxml.jackson.databind.introspect.AnnotatedClass;
import com.fasterxml.jackson.databind.introspect.BeanDescription;
import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;
import com.fasterxml.jackson.annotation.JsonNaming;

// 定义一个带有@JsonNaming注解的示例类
@JsonNaming(PropertyNamingStrategy.KebabCaseStrategy.class)
public class MyClass {
    public String firstName;
    public String lastName;
}

// 定义一个没有@JsonNaming注解的示例类
public class AnotherClass {
    public String someProperty;
}

public class NamingStrategyIntrospection {

    public static void main(String[] args) {
        ObjectMapper mapper = new ObjectMapper();

        // 1. 内省 MyClass
        System.out.println("--- Introspecting MyClass ---");
        introspectNamingStrategy(mapper, MyClass.class);

        // 2. 内省 AnotherClass
        System.out.println("\n--- Introspecting AnotherClass ---");
        introspectNamingStrategy(mapper, AnotherClass.class);
    }

    public static void introspectNamingStrategy(ObjectMapper mapper, Class<?> targetClass) {
        // 获取SerializationConfig
        SerializationConfig config = mapper.getSerializationConfig();

        // 内省类注解，获取BeanDescription
        BeanDescription beanDesc = config.introspectClassAnnotations(targetClass);

        // 从BeanDescription获取AnnotatedClass
        AnnotatedClass annotatedClass = beanDesc.getClassInfo();

        // 实例化JacksonAnnotationIntrospector
        JacksonAnnotationIntrospector jai = new JacksonAnnotationIntrospector();

        // 查找命名策略
        Class<? extends PropertyNamingStrategy> namingStrategyClass = jai.findNamingStrategy(annotatedClass);

        if (namingStrategyClass != null) {
            System.out.println("Class '" + targetClass.getSimpleName() + "' uses PropertyNamingStrategy: " + namingStrategyClass.getName());
            // 如果需要PropertyNamingStrategy的实例，可以通过反射创建
            try {
                PropertyNamingStrategy strategyInstance = namingStrategyClass.getDeclaredConstructor().newInstance();
                System.out.println("Strategy instance created: " + strategyInstance.getClass().getSimpleName());
            } catch (Exception e) {
                System.err.println("Failed to instantiate naming strategy: " + e.getMessage());
            }
        } else {
            System.out.println("Class '" + targetClass.getSimpleName() + "' does not have a specific @JsonNaming strategy. It will use ObjectMapper's default or no strategy.");
        }
    }
}

--- Introspecting MyClass ---
Class 'MyClass' uses PropertyNamingStrategy: com.fasterxml.jackson.databind.PropertyNamingStrategy$KebabCaseStrategy
Strategy instance created: KebabCaseStrategy

--- Introspecting AnotherClass ---
Class 'AnotherClass' does not have a specific @JsonNaming strategy. It will use ObjectMapper's default or no strategy.