java实现json文件的读取和解析

	<dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.4</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.37</version>
     	</dependency>





import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import lombok.Data;
import org.apache.commons.io.FileUtils;
import org.springframework.core.io.ClassPathResource;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;

import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Collectors;

public class MainApplication {

    public static Map<String, List<KeyValue>> map = new ConcurrentHashMap<>(28);


    public static void main(String[] args) throws IOException {

        String value = getValueForKeyAndId("channel", 1);
        System.out.println(value);
        List<String> strings = getValuesForKey("channel");
        System.out.println(strings);

    }


    /**
     * 通过key 获取所有value值
     * @param key
     * @return
     * @throws IOException
     */
    public static List<String> getValuesForKey(String key) throws IOException {
        List<KeyValue> list = getKeyValues(key);
        if (CollectionUtils.isEmpty(list)) {return null;}
        List<String> valueStrings = list.stream().map(s -> s.getValue()).collect(Collectors.toList());
        return valueStrings;

    }

    /**
     * 通过key和id获取value值
     * @return
     */
    public static String getValueForKeyAndId(String key,Integer id) throws IOException {
        List<KeyValue> list = getKeyValues(key);

        if (CollectionUtils.isEmpty(list)) {return null;}

        for (KeyValue keyValue : list) {
            if (keyValue.getId() == id) {
                return keyValue.getValue();
            }
        }
        return null;

    }





    public static List<KeyValue> getKeyValues(String key) throws IOException {
        if (StringUtils.isEmpty(key)){return null;}

        if (CollectionUtils.isEmpty(map)) {
            readJsonData();
        }
        List<KeyValue> list = map.get(key);
        return list;
    }

    /**
     * 读取文件数据加入到map缓存中
     * @throws IOException
     */
    public static void readJsonData() throws IOException {
        ClassPathResource resource = new ClassPathResource("adConfig.json");
        File file = resource.getFile();
        String jsonString = FileUtils.readFileToString(file);


        JSONObject jsonObject = JSONObject.parseObject(jsonString);

        Set<String> keySet = jsonObject.keySet();
        for (String s : keySet) {

            String stringArray = jsonObject.getJSONArray(s).toJSONString();
            List<KeyValue> keyValues = JSONArray.parseArray(stringArray, KeyValue.class);
            map.put(s, keyValues);
        }
    }


    @Data
    static class KeyValue{
        private int id;
        private String value;
    }

}


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