JAXB中动态获取Java对象QName并创建JAXBElement的反射策略

@XmlRegistry
public class ObjectFactory {
    private final static QName ABC_QNAME = new QName("http://www", "request1");
    // ... 其他 QName 定义

    public JAXBElement<ABC> createABC(ABC value) {
        return new JAXBElement<>(ABC_QNAME, ABC.class, value);
    }
    // ... 其他 create 方法
}

import org.springframework.core.ResolvableType;
import org.springframework.util.ClassUtils;
import org.springframework.lang.Nullable;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferFactory;
import org.springframework.oxm.Marshaller;
import org.springframework.oxm.jaxb.JaxbUtils;
import org.springframework.oxm.jaxb.JaxbContextImpl; // 假设 JaxbUtils 内部可能使用
import org.springframework.oxm.jaxb.JAXBContextUtils; // 如果有更通用的JAXBContext创建工具

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBElement;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.annotation.XmlRegistry;
import javax.xml.namespace.QName;
import java.io.OutputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;

// 假设 ObjectFactory 和 ABC 类已经生成
// import com.yourpackage.ObjectFactory;
// import com.yourpackage.ABC;

public class JaxbEncoder {

    // 假设 ObjectFactory 类的完整路径
    private static final String OBJECT_FACTORY_CLASS_NAME = "com.yourpackage.ObjectFactory";
    private Object objectFactoryInstance; // 缓存 ObjectFactory 实例

    public JaxbEncoder() throws InstantiationException, IllegalAccessException, ClassNotFoundException {
        // 在构造器中初始化 ObjectFactory 实例，避免每次调用 encodeValue 都创建
        Class<?> objectFactoryClass = Class.forName(OBJECT_FACTORY_CLASS_NAME);
        this.objectFactoryInstance = objectFactoryClass.newInstance();
    }

    // 假设 initMarshaller 方法已定义
    private Marshaller initMarshaller(JAXBContext jaxbContext) throws JAXBException {
        Marshaller marshaller = jaxbContext.createMarshaller();
        // 可以设置其他 Marshaller 属性，例如格式化输出
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
        return marshaller;
    }

    public DataBuffer encodeValue(Object value, DataBufferFactory bufferFactory, ResolvableType valueType, @Nullable String mimeType, @Nullable Map<String, Object> hints) {
        boolean release = true;
        DataBuffer buffer = bufferFactory.allocateBuffer(1024);
        try {
            OutputStream outputStream = buffer.asOutputStream();
            Class<?> clazz = ClassUtils.getUserClass(value); // 获取用户定义的实际类

            JAXBContext jaxbContext = JaxbUtils.createJaxbContext(); // 假设 JaxbUtils 提供了创建 JAXBContext 的方法
            Marshaller marshaller = initMarshaller(jaxbContext);

            // 1. 尝试通过 ObjectFactory 反射获取 JAXBElement
            JAXBElement<Object> jaxbElement = createJAXBElementUsingReflection(value, clazz);

            if (jaxbElement == null) {
                // 如果反射失败（例如，没有对应的create方法），则尝试其他方式或抛出异常
                throw new EncodingException("无法通过ObjectFactory为类 " + clazz.getName() + " 创建JAXBElement。");
            }

            marshaller.marshal(jaxbElement, outputStream);
            release = false;
            return buffer;
        } catch (Exception ex) {
            throw new EncodingException("无法将 " + value.getClass() + " 编组为XML", ex);
        } finally {
            if (release) {
                // 确保在异常情况下释放资源
                buffer.release();
            }
        }
    }

    @SuppressWarnings("unchecked")
    private JAXBElement<Object> createJAXBElementUsingReflection(Object value, Class<?> valueClass)
            throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
        // 构造 create 方法名，例如：ABC -> createABC
        String methodName = "create" + valueClass.getSimpleName();

        // 获取 ObjectFactory 类的 Method 对象
        // 注意：create 方法通常接受一个参数，其类型与 POJO 类型相同
        Method createMethod = objectFactoryInstance.getClass().getMethod(methodName, valueClass);

        // 调用 create 方法，并传入 value 对象
        // createMethod.invoke 返回的是 JAXBElement<T>，这里强制转换为 JAXBElement<Object>
        return (JAXBElement<Object>) createMethod.invoke(objectFactoryInstance, value);
    }
}

// 假设 EncodingException 是自定义的运行时异常
class EncodingException extends RuntimeException {
    public EncodingException(String message, Throwable cause) {
        super(message, cause);
    }
    public EncodingException(String message) {
        super(message);
    }
}