package com.jake.test;
import org.springframework.util.ClassUtils;
import org.springframework.util.ReflectionUtils;
import java.beans.Introspector;
import java.lang.invoke.SerializedLambda;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
public class ReflectionUtil {
private static final Map<SerializableFunction<?, ?>, Field> CACHE = new ConcurrentHashMap<>();
public static <T, R> String getFieldName(SerializableFunction<T, R> function) {
Field field = ReflectionUtil.getField(function);
return field.getName();
}
public static Field getField(SerializableFunction<?, ?> function) {
return CACHE.computeIfAbsent(function, ReflectionUtil::findField);
}
public static Field findField(SerializableFunction<?, ?> function) {
Field field = null;
String fieldName = null;
try {
// 第1步 获取SerializedLambda
Method method = function.getClass().getDeclaredMethod("writeReplace");
method.setAccessible(Boolean.TRUE);
SerializedLambda serializedLambda = (SerializedLambda) method.invoke(function);
// 第2步 implMethodName 即为Field对应的Getter方法名
String implMethodName = serializedLambda.getImplMethodName();
if (implMethodName.startsWith("get") && implMethodName.length() > 3) {
fieldName = Introspector.decapitalize(implMethodName.substring(3));
} else if (implMethodName.startsWith("is") && implMethodName.length() > 2) {
fieldName = Introspector.decapitalize(implMethodName.substring(2));
} else if (implMethodName.startsWith("lambda$")) {
throw new IllegalArgumentException("SerializableFunction不能传递lambda表达式,只能使用方法引用");
} else {
throw new IllegalArgumentException(implMethodName + "不是Getter方法引用");
}
// 第3步 获取的Class是字符串,并且包名是“/”分割,需要替换成“.”,才能获取到对应的Class对象
String declaredClass = serializedLambda.getImplClass().replace("/", ".");
Class<?> aClass = Class.forName(declaredClass, false, ClassUtils.getDefaultClassLoader());
// 第4步 Spring 中的反射工具类获取Class中定义的Field
field = ReflectionUtils.findField(aClass, fieldName);
} catch (Exception e) {
e.printStackTrace();
}
// 第5步 如果没有找到对应的字段应该抛出异常
if (field != null) {
return field;
}
throw new NoSuchFieldError(fieldName);
}
}
参考