Byte Buddy - 定义构造函数并调用超类和初始化字段

Question

我有一个类，例如：

public class Sample{

private String a;
private String b;

public Sample(String a, String b)
{
    this.a = a;
    this.b = b;
}
 public String getA() {return a;}
 public String getB() {return b;}
}

我想创建一个从 Sample 类继承的动态类，并向其中添加字段（字符串字段）。

我试图做：

DynamicType.Builder<? extends Sample> classBuilder = new ByteBuddy()
        .subclass(Sample.class, ConstructorStrategy.Default.NO_CONSTRUCTORS)
        .name("sampleSon");

classBuilder.defineConstructor(Visibility.PUBLIC)
        .withParameters(String.class, String.class, String.class)
        .intercept(MethodCall.invoke(Sample.class.getConstructor(String.class, String.class))
                .withArgument(0, 1)
                .andThen(FieldAccessor.ofField("c").setsArgumentAt(2)));

但是当我尝试从这个类创建一个实例时：

Class<? extends Sample> newSampleClass= classBuilder.make().load(ClassLoader.getSystemClassLoader()).getLoaded();
Sample sample = newSampleClass.getConstructor(String.class, String.class, String.class).newInstance("a", "b", "c");

它抛出一个异常：

public class Sample{

private String a;
private String b;

public Sample(String a, String b)
{
    this.a = a;
    this.b = b;
}
 public String getA() {return a;}
 public String getB() {return b;}
}

我究竟做错了什么？我想创建一个类，这样：

public class SampleSon extends Sample {
     private String c;
     public SampleSon(String a, String b, String c) {
       super(a,b);
       this.c = c;
     }

     public String getC() { return c;}
}

Answer 1

c在构造函数定义中开始使用字段之前，您无需定义字段。

Class<? extends Sample> clazz = new ByteBuddy()
        .subclass(Sample.class, ConstructorStrategy.Default.NO_CONSTRUCTORS)
        .name("SampleSon")
        .defineField("c", String.class, Visibility.PRIVATE)
        .defineConstructor(Visibility.PUBLIC)
        .withParameters(String.class, String.class, String.class)
        .intercept(MethodCall.invoke(Sample.class.getConstructor(String.class, String.class))
                .withArgument(0, 1)
                .andThen(FieldAccessor.ofField("c").setsArgumentAt(2)))
        .make()
        .load(ClassLoader.getSystemClassLoader())
        .getLoaded();

注意：您还需要根据ByteBuddyjavadoc 链接所有方法调用。