package cn.mb.cloud.common.sentinel.fallback;
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import cn.mb.cloud.common.core.constant.enums.ErrorCodeConstants;
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import cn.mb.cloud.common.core.util.ResponseData;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.cglib.proxy.MethodInterceptor;
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import org.springframework.cglib.proxy.MethodProxy;
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import java.lang.reflect.Method;
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import java.lang.reflect.ParameterizedType;
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import java.lang.reflect.Type;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.HashSet;
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import java.util.List;
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import java.util.Map;
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import java.util.Set;
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/**
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* Safe replacement for the common Sentinel Feign fallback.
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*
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* <p>The dependency version assumes every generic return type is a Class. That
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* is false for declarations such as {@code Map<String, Object>}, whose runtime
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* type is {@link ParameterizedType}; the failed cast used to hide the original
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* downstream exception behind an AssertionError.</p>
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*/
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public class DefaultFeignFallback<T> implements MethodInterceptor {
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private static final Logger log = LoggerFactory.getLogger(DefaultFeignFallback.class);
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private final Class<T> targetType;
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private final String targetName;
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private final Throwable cause;
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public DefaultFeignFallback(Class<T> targetType, String targetName, Throwable cause) {
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this.targetType = targetType;
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this.targetName = targetName;
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this.cause = cause;
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}
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@Override
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public Object intercept(Object object, Method method, Object[] arguments, MethodProxy methodProxy) {
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log.error("FunFeignFallback:[{}.{}] serviceId:[{}] message:[{}]",
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targetType.getName(), method.getName(), targetName, cause == null ? null : cause.getMessage());
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Type declaredReturnType = method.getGenericReturnType();
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Class<?> returnType = rawType(declaredReturnType);
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Object data = defaultValue(returnType);
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// Only methods that explicitly declare ResponseData may receive a
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// ResponseData fallback. Returning it from Map/List methods causes a
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// second ClassCastException in the Feign proxy.
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if (ResponseData.class.equals(returnType)) {
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Type dataType = firstTypeArgument(declaredReturnType);
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return ResponseData.builder()
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.code(ErrorCodeConstants.FAIL.getValue())
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.msg("系统降级,请稍后再试！")
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.data(defaultValue(rawType(dataType)))
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.build();
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}
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return data;
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}
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private Type firstTypeArgument(Type type) {
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if (type instanceof ParameterizedType) {
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Type[] arguments = ((ParameterizedType) type).getActualTypeArguments();
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if (arguments.length > 0) return arguments[0];
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}
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return null;
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}
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private Class<?> rawType(Type type) {
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if (type instanceof Class<?>) return (Class<?>) type;
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if (type instanceof ParameterizedType) return rawType(((ParameterizedType) type).getRawType());
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return Object.class;
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}
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private Object defaultValue(Class<?> type) {
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if (List.class.isAssignableFrom(type)) return new ArrayList<Object>();
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if (Set.class.isAssignableFrom(type)) return new HashSet<Object>();
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if (Map.class.isAssignableFrom(type)) return new HashMap<Object, Object>();
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if (Boolean.class.equals(type) || boolean.class.equals(type)) return Boolean.FALSE;
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if (type.isPrimitive()) return primitiveDefault(type);
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return null;
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}
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private Object primitiveDefault(Class<?> type) {
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if (char.class.equals(type)) return Character.valueOf('\0');
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if (byte.class.equals(type)) return Byte.valueOf((byte) 0);
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if (short.class.equals(type)) return Short.valueOf((short) 0);
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if (int.class.equals(type)) return Integer.valueOf(0);
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if (long.class.equals(type)) return Long.valueOf(0L);
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if (float.class.equals(type)) return Float.valueOf(0F);
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if (double.class.equals(type)) return Double.valueOf(0D);
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return null;
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}
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}
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