下面是一个使用ByteBuddy创建带有构造函数的枚举类的示例代码:
import net.bytebuddy.ByteBuddy;
import net.bytebuddy.description.ModifierReviewable;
import net.bytebuddy.description.enumeration.EnumerationDescription;
import net.bytebuddy.description.enumeration.EnumerationDescription.ForLoadedEnumeration;
import net.bytebuddy.description.enumeration.EnumerationDescription.Latent;
import net.bytebuddy.description.enumeration.FieldDescription;
import net.bytebuddy.description.field.FieldDescription.ForLoadedField;
import net.bytebuddy.dynamic.DynamicType;
import net.bytebuddy.implementation.FixedValue;
import net.bytebuddy.implementation.Implementation;
import net.bytebuddy.implementation.MethodDelegation;
import net.bytebuddy.matcher.ElementMatchers;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
public class EnumConstructorExample {
    public enum MyEnum {
        VALUE1("first value", 1),
        VALUE2("second value", 2);
        private final String name;
        private final int value;
        MyEnum(String name, int value) {
            this.name = name;
            this.value = value;
        }
        public String getName() {
            return name;
        }
        public int getValue() {
            return value;
        }
    }
    public static void main(String[] args) throws Exception {
        // 定义枚举类描述符
        Latent enumDescription = EnumerationDescription
                .ForLoadedEnumeration.of(MyEnum.class);
        // 创建ByteBuddy实例
        ByteBuddy byteBuddy = new ByteBuddy();
        // 创建枚举类的构造函数
        Implementation.MethodDefinition.ConstructorDefinition constructorDefinition =
                byteBuddy.subclass(MyEnum.class)
                        .defineConstructor(ModifierReviewable.EMPTY_MASK)
                        .withParameters(String.class, int.class)
                        .intercept(MethodDelegation.to(ConstructorInterceptor.class))
                        .defineConstructor(ModifierReviewable.EMPTY_MASK)
                        .intercept(MethodDelegation.to(ConstructorInterceptor.class))
                        .method(ElementMatchers.isDeclaredBy(MyEnum.class))
                        .intercept(MethodDelegation.to(ConstructorInterceptor.class));
        // 创建枚举类的字节码
        DynamicType.Unloaded dynamicType = constructorDefinition.make();
        // 加载枚举类
        Class> loadedType = dynamicType.load(EnumConstructorExample.class.getClassLoader())
                .getLoaded();
        // 获取枚举类的构造函数
        Constructor>[] constructors = loadedType.getDeclaredConstructors();
        // 创建枚举实例并调用方法
        for (Constructor> constructor : constructors) {
            constructor.setAccessible(true);
            MyEnum enumInstance = (MyEnum) constructor.newInstance("new value", 3);
            System.out.println("Enum name: " + enumInstance.getName());
            System.out.println("Enum value: " + enumInstance.getValue());
        }
    }
    public static class ConstructorInterceptor {
        public static MyEnum intercept(@FieldDescription.ForLoadedField(declaringType = MyEnum.class) Field field,
                                       @FieldDescription.ForLoadedField(declaringType = MyEnum.class) Object defaultValue) {
            if (field.getType() == String.class) {
                return MyEnum.valueOf(((String) defaultValue).toUpperCase());
            } else if (field.getType() == int.class) {
                return MyEnum.values()[(int) defaultValue];
            }
            throw new IllegalArgumentException("Unsupported field type");
        }
    }
}
   在上面的示例中,我们首先定义了一个名为MyEnum的枚举类,它具有两个字段和一个构造函数。然后,我们使用ByteBuddy创建一个新的枚举类,并定义了一个名为ConstructorInterceptor的拦截器类来实现构造函数。
在ConstructorInterceptor类中,我们定义了一个名为intercept的方法,该方法接受枚举类的字段和默认值作为参数。在方法中,我们根据字段的类型选择合适的枚举实例,并返回它。
最后,我们使用intercept方法来定义构造函数的实现,并使用make方法创建枚举类的字节码。然后,我们加载枚举类并创建实例,并调用其中的方法来验证结果。
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