技術標籤：java學習筆記ymljavaSnakeYamlyml

1. 如何使用SnakeYAML來讀取YAML（YML為其簡寫）配置檔案；
2. 讀取後，裝載成Map，而Map如何儲存的配置檔案的資料。

Snake POM引入

<dependency>
    <groupId>org.yaml</groupId>
    <artifactId>snakeyaml</artifactId>
    <version>1.27</version>
</dependency>

讀取YAML配置檔案

InputStream in = this.getClass().getClassLoader().getResourceAsStream(DEFAULT_RESOURCES);
Yaml yaml = new Yaml();
Map<String, Object> load = yaml.loadAs(in, Map.class);
 

Map是如何儲存的配置檔案資料

以下面的.yml配置檔案為例：

log:
  location: /home/iwu/runningstat
  cache:
    path: /home/iwu/runningstat/temp
  local: false
appid: 123
server:
  port: 2020
app:
  testList:
    -
      name: wangchao
      age: 23
    -
      name: sff
      age: 20

使用SnakeYAML進行裝載，例項化成Map物件（確切的說，應該是Map的子類，LinkedHashMap）。值得注意的是，要裝載如此複雜的配置檔案的，必須使用Map的巢狀，即：Map巢狀Map。

先來一段測試程式碼：

    private void printYmalMap(String prefixKey, Map<String, Object> map) {
        String fullKey = "";
        for (String key : map.keySet()) {
            fullKey = prefixKey == null || "".equals(prefixKey) ? key : prefixKey + "." + key;
            Object value = map.get(key);
            if (value instanceof Map) {
                //System.out.println("there is a map  " + prefixKey + "." + key);
                printYmalMap(fullKey, (Map) value);
            } else if (value instanceof List) {
                System.out.println("there is a list  " + fullKey);
            } else {
                System.out.println("there is a  "+value.getClass().getName() +"...   "+ fullKey);
            }
        }
    }
 

看看Snake解析上面yml檔案列印結果

分析完成，看看完整的yaml載入 程式碼。這裡我們將基本型別轉換為了String型別。如有需要我們可以進一步進行處理。

import org.yaml.snakeyaml.Yaml;

import java.io.InputStream;
import java.util.*;

public class YamlResourcesProcessor{
    private static final String DEFAULT_RESOURCES = "application.yml";
    /**
     * ymal 檔案中資料解析快取
     */
    private static volatile Map<String, String> cache = Collections.synchronizedMap(new HashMap<>());

    public YamlResourcesProcessor() {
        load();
    }

    private void load() {
        InputStream in = this.getClass().getClassLoader().getResourceAsStream(DEFAULT_RESOURCES);
        Yaml yaml = new Yaml();
        Map<String, Object> load = yaml.loadAs(in, Map.class);
        printYmalMap(null, load);
        cacheYmal(null, load);
    }

    private void cacheYmal(String prefixKey, Map<String, Object> map) {
        String fullKey = "";
        for (String key : map.keySet()) {
            Object value = map.get(key);
            fullKey = prefixKey == null || "".equals(prefixKey) ? key : prefixKey + "." + key;
            if (value instanceof Map) {
                cacheYmal(fullKey, (Map) value);
            } else if (value instanceof List) {
                // Ymal轉Map 暫時不處理List
                cache.put(fullKey,  String.valueOf(value));
                //continue;
            } else {
                cache.put(fullKey,  String.valueOf(value));
            }
        }
    }

    private void printYmalMap(String prefixKey, Map<String, Object> map) {
        String fullKey = "";
        for (String key : map.keySet()) {
            fullKey = prefixKey == null || "".equals(prefixKey) ? key : prefixKey + "." + key;
            Object value = map.get(key);
            if (value instanceof Map) {
                //System.out.println("there is a map  " + prefixKey + "." + key);
                printYmalMap(fullKey, (Map) value);
            } else if (value instanceof List) {
                System.out.println("there is a list  " + fullKey);
            } else {
                System.out.println("there is a  "+value.getClass().getName() +"...   "+ fullKey);
            }
        }
    }

    public Map<String, String> getResources() {
        return cache;
    }
}