kotlin 泛型问题

Json.kt

/*
 * Copyright (c) 2018. Xi'an iRain IOT Technology service CO., Ltd (ShenZhen). All Rights Reserved.
 */

package com.parkingwang.iop.api.json

import com.google.gson.Gson
import com.google.gson.GsonBuilder
import com.google.gson.reflect.TypeToken
import com.parkingwang.iop.api.services.park.objects.Version
import org.itishka.gsonflatten.FlattenTypeAdapterFactory
import java.util.ArrayList

/**
 * GSON 库的一些类型解析的兼容处理。
 *
 * @author 黄浩杭 ([email protected])
 * @since 2.12
 */
object Json {
    private val BOOLEAN_AS_INT_ADAPTER = BooleanAsIntAdapter()
    private val COMPAT_FLOW_ADAPTER = CompatFloatAdapter()

    val GSON: Gson = GsonBuilder()
            .registerTypeAdapterFactory(ValueEnumAdapterFactory())
            .create()

    fun <T> parseArray(json: String, cls: Class<T>): ArrayList<T>? {
        val type = TypeToken.getParameterized(ArrayList::class.java, cls).type
        return GSON.fromJson<ArrayList<T>>(json, type)
    }

    fun <T> parseObject(json: String, cls: Class<T>): T? {
        return GSON.fromJson(json, cls)
    }

    fun <T> toJson(`object`: T): String {
        return GSON.toJson(`object`)
    }
}

ValueEnum.java

/*
 * Copyright (c) 2018. Xi'an iRain IOT Technology service CO., Ltd (ShenZhen). All Rights Reserved.
 */

package com.parkingwang.iop.api.json

/**
 * @author 黄浩杭 ([email protected])
 * @since 2018-02-06 1.13
 */
interface ValueEnum {
    /**
     * 返回枚举对应的数值
     *
     * @return 枚举值
     */
    val value: Int
}

ValueEnumAdapter.java

/*
 * Copyright (c) 2018. Xi'an iRain IOT Technology service CO., Ltd (ShenZhen). All Rights Reserved.
 */

package com.parkingwang.iop.api.json;

import com.google.gson.TypeAdapter;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonToken;
import com.google.gson.stream.JsonWriter;

import java.io.IOException;

/**
 * 按值解析为枚举类型
 *
 * @author 黄浩杭 ([email protected])
 * @version 2.8
 * @since 2018-02-06 1.13
 */
public class ValueEnumAdapter<T extends Enum<T>> extends TypeAdapter<T> {
    private final T[] mConstants;

    public ValueEnumAdapter(Class<T> enumType) {
        mConstants = enumType.getEnumConstants();
    }

    @Override
    public void write(JsonWriter out, T t) throws IOException {
        if (t == null) {
            out.value("");
        } else {
            out.value(String.valueOf(((ValueEnum) t).getValue()));
        }
    }

    @Override
    public T read(JsonReader in) throws IOException {
        JsonToken peek = in.peek();
        final int value;
        switch (peek) {
            case NUMBER:
                value = in.nextInt();
                break;
            case STRING:
                final String string = in.nextString();
                if (string.isEmpty()) {
                    return null;
                }
                value = Integer.parseInt(string);
                break;
            case NULL:
                return null;
            default:
                throw new IllegalStateException("Expected NUMBER but was " + peek + " " + in.getPath());
        }
        for (T constant : mConstants) {
            if (((ValueEnum) constant).getValue() == value) {
                return constant;
            }
        }
        return null;
    }
}

ValueEnumAdapter2.kt

/*
 * Copyright (c) 2018. Xi'an iRain IOT Technology service CO., Ltd (ShenZhen). All Rights Reserved.
 */

package com.parkingwang.iop.api.json

import com.google.gson.TypeAdapter
import com.google.gson.stream.JsonReader
import com.google.gson.stream.JsonToken
import com.google.gson.stream.JsonWriter

import java.io.IOException

/**
 * 按值解析为枚举类型
 *
 * @author 黄浩杭 ([email protected])
 * @version 2.8
 * @since 2018-02-06 1.13
 */
class ValueEnumAdapter<T : Enum<T>>(enumType: Class<T>) : TypeAdapter<T>() {
    private val constants: Array<T> = enumType.enumConstants

    @Throws(IOException::class)
    override fun write(out: JsonWriter, t: T?) {
        if (t == null) {
            out.value("")
        } else {
            out.value((t as ValueEnum).value.toString())
        }
    }

    @Throws(IOException::class)
    override fun read(`in`: JsonReader): T? {
        val peek = `in`.peek()
        val value: Int
        value = when (peek) {
            JsonToken.NUMBER -> `in`.nextInt()
            JsonToken.STRING -> {
                val string = `in`.nextString()
                if (string.isEmpty()) {
                    return null
                }
                Integer.parseInt(string)
            }
            JsonToken.NULL -> return null
            else -> throw IllegalStateException("Expected NUMBER but was " + peek + " " + `in`.path)
        }
        for (constant in constants) {
            if ((constant as ValueEnum).value == value) {
                return constant
            }
        }
        return null
    }
}

ValueEnumAdapter3.kt

/*
 * Copyright (c) 2018. Xi'an iRain IOT Technology service CO., Ltd (ShenZhen). All Rights Reserved.
 */

package com.parkingwang.iop.api.json

import com.google.gson.TypeAdapter
import com.google.gson.stream.JsonReader
import com.google.gson.stream.JsonToken
import com.google.gson.stream.JsonWriter

import java.io.IOException

/**
 * 按值解析为枚举类型
 *
 * @author 黄浩杭 ([email protected])
 * @version 2.8
 * @since 2018-02-06 1.13
 */
class ValueEnumAdapter<T>(enumType: Class<T>) : TypeAdapter<T>() where T : Enum<T>, T : ValueEnum {
    private val constants: Array<T> = enumType.enumConstants

    @Throws(IOException::class)
    override fun write(out: JsonWriter, t: T?) {
        if (t == null) {
            out.value("")
        } else {
            out.value(t.value.toString())
        }
    }

    @Throws(IOException::class)
    override fun read(`in`: JsonReader): T? {
        val peek = `in`.peek()
        val value: Int
        value = when (peek) {
            JsonToken.NUMBER -> `in`.nextInt()
            JsonToken.STRING -> {
                val string = `in`.nextString()
                if (string.isEmpty()) {
                    return null
                }
                Integer.parseInt(string)
            }
            JsonToken.NULL -> return null
            else -> throw IllegalStateException("Expected NUMBER but was " + peek + " " + `in`.path)
        }
        for (constant in constants) {
            if (constant.value == value) {
                return constant
            }
        }
        return null
    }
}

ValueEnumAdapterFactory.java

/*
 * Copyright (c) 2018. Xi'an iRain IOT Technology service CO., Ltd (ShenZhen). All Rights Reserved.
 */

package com.parkingwang.iop.api.json;

import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.reflect.TypeToken;

/**
 * 值类型的枚举解析处理
 *
 * @author 黄浩杭 ([email protected])
 * @since 2018-02-06 1.13
 */
public class ValueEnumAdapterFactory implements TypeAdapterFactory {
    @Override
    public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
        Class<?> rawType = type.getRawType();
        if (rawType.isEnum() && ValueEnum.class.isAssignableFrom(rawType)) {
            return (TypeAdapter<T>) new ValueEnumAdapter<>((Class<? extends Enum>)rawType);
        }
        return null;
    }
}