net.paoding.rose.jade.statement.GenericUtils Maven / Gradle / Ivy

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package net.paoding.rose.jade.statement;

import org.apache.commons.lang.ArrayUtils;

import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Parameter;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

/**
 * 实现工具类，检查参数化类型的参数类型。
 * @author han.liao
 * @author 王志亮 [[email protected]]
 */
@SuppressWarnings({"rawtypes"})
public class GenericUtils {

    private static final Class[] EMPTY_CLASSES = new Class[0];

    /**
     * 从参数, 返回值, 基类的: Generic 类型信息获取传入的实际类信息。
     * @param genericType - Generic 类型信息
     * @param daoMetaData
     * @return 实际类信息
     */
    public static Class[] getActualClass(Type genericType, DAOMetaData daoMetaData) {

        if (genericType instanceof ParameterizedType) {

            Type[] actualTypes = ((ParameterizedType) genericType).getActualTypeArguments();
            Class[] actualClasses = new Class[actualTypes.length];

            for (int i = 0; i < actualTypes.length; i++) {
                Type actualType = actualTypes[i];
                if (actualType instanceof Class) {
                    actualClasses[i] = (Class) actualType;
                } else if (actualType instanceof GenericArrayType) {
                    Type componentType = ((GenericArrayType) actualType).getGenericComponentType();
                    actualClasses[i] = Array.newInstance((Class) componentType, 0).getClass();
                } else if (actualType instanceof TypeVariable) {
                    actualClasses[i] = resolveTypeVariable(daoMetaData, (TypeVariable) actualType);
                } else {
                    throw new IllegalArgumentException("unsupport DAO method: " + daoMetaData.getDAOClass().getName());
                }
            }

            return actualClasses;
        }

        return EMPTY_CLASSES;
    }

    /**
     * DAO方法实际的返回类型
     * @param smd
     * @return
     */
    public static Class getReturnType(StatementMetaData smd) {
        Method method = smd.getMethod();
        DAOMetaData daoMetaData = smd.getDAOMetaData();
        if (method.getGenericReturnType() instanceof TypeVariable) {
            TypeVariable v = (TypeVariable) method.getGenericReturnType();
            return resolveTypeVariable(daoMetaData, v);
        }
        return method.getReturnType();
    }

    /**
     * 求类型变量的值
     * @param daoMetaData
     * @param key
     * @return
     */
    public static final Class resolveTypeVariable(DAOMetaData daoMetaData, TypeVariable key) {
        Map refs = new HashMap<>();

        // 
        List allSuperTypes = new LinkedList();
        allSuperTypes.addAll(Arrays.asList(daoMetaData.getDAOClass().getGenericInterfaces()));
        for (int i = 0; i < allSuperTypes.size(); i++) {
            Type type = allSuperTypes.get(i);
            if (type instanceof ParameterizedType) {
                ParameterizedType parameterizedType = ((ParameterizedType) type);
                Class interfaceClass = (Class) parameterizedType.getRawType();
                int j = 0;
                for (Type actualTypeArgument : parameterizedType.getActualTypeArguments()) {
                    TypeVariable v = interfaceClass.getTypeParameters()[j++];
                    refs.put(v, actualTypeArgument);
                    // System.out.println("put " + v + "  --->  " + actualTypeArgument);
                }

                for (Type t : interfaceClass.getGenericInterfaces()) {
                    if (!allSuperTypes.contains(t)) {
                        allSuperTypes.add(t);
                    }
                }
            } else {
                for (Type t : ((Class) type).getGenericInterfaces()) {
                    if (!allSuperTypes.contains(t)) {
                        allSuperTypes.add(t);
                    }
                }
            }
        }

        Type returnType = key;
        while (true) {
            Type old = returnType;
            returnType = refs.get(returnType);
            if (returnType instanceof Class) {
                return (Class) returnType;
            }
            if (returnType == null) {
                returnType = old;
                return (Class) ((TypeVariable) returnType).getBounds()[0];
            }
        }
    }

    /**
     * 收集类的所有常量。
     * @param clazz          - 收集目标
     * @param findAncestor   - 是否查找父类
     * @param findInterfaces - 是否查找接口
     * @return {@link Map} 包含类的所有常量
     */
    public static Map getConstantFrom(
            Class clazz, // NL
            boolean findAncestor, boolean findInterfaces) {

        HashMap map = new HashMap();

        if (findInterfaces) {
            for (Class interfaceClass : clazz.getInterfaces()) {
                fillConstantFrom(interfaceClass, map);
            }
        }

        if (findAncestor) {
            Class superClass = clazz;
            while (superClass != null) {
                fillConstantFrom(superClass, map);
                superClass = superClass.getSuperclass();
            }
        }

        fillConstantFrom(clazz, map);

        return map;
    }

    // 填充静态常量
    protected static void fillConstantFrom(Class clazz, HashMap map) {

        Field fields[] = clazz.getDeclaredFields();
        for (Field field : fields) {
            if (field.isSynthetic()) {
                continue; // 忽略系统常量
            }

            int modifiers = field.getModifiers();
            if (!Modifier.isStatic(modifiers)) {
                continue; // 忽略非静态常量
            }

            try {
                if (field.isAccessible()) {
                    field.setAccessible(true);
                }
                map.put(field.getName(), field.get(null));

            } catch (SecurityException | IllegalAccessException e) {
                // Do nothing
            }
        }
    }

    /**
     * 获取方法的参数名列表

     * 如果编译时未开启 parameters,则返回 [arg0,arg1,arg2....]
     * @param method
     * @return
     */
    public static String[] getMethodParamNames(Method method) {
        Parameter[] parameters = method.getParameters();
        if (ArrayUtils.isEmpty(parameters)) return new String[0];
        return Arrays.stream(parameters).map(Parameter::getName).toArray(String[]::new);
    }
}