BerkeleyDB-JE Hello World（使用BaseAPI）

在進一步介紹JE之前，我們先看個BaseAPI版的Hello World，這個例子演示了JE最一般的使用方法，打開環境和Database，持久化數據，查詢數據，關閉環境和Database。

/**
 * 用BaseAPI保存和獲取數據
 * @author mengyang
 *
 */
public class HelloWorldByBaseAPI {

	private File file = new File("C:/Users/mengyang/workspace/je");
	private Environment env;
	private Database database;

	//建立環境
	private void setUp(){

		EnvironmentConfig envConfig = new EnvironmentConfig();
		envConfig.setAllowCreate(true); 
		env = new Environment(file, envConfig);

		DatabaseConfig dbConfig = new DatabaseConfig();
		dbConfig.setAllowCreate(true);
		database = env.openDatabase(null, "baseAPIDemo", dbConfig);
	}

	//保存數據
	private void save(){
		String key = "BaseAPI";
		String value = "Hello World!";

		try {
			DatabaseEntry keyEntry = new DatabaseEntry(key.getBytes("utf-8"));//鍵
			DatabaseEntry valueEntry = new DatabaseEntry(value.getBytes("utf-8"));//值
			database.put(null, keyEntry, valueEntry);//保存鍵值對
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
	}

	//檢索數據
	private void get(){
		String key = "BaseAPI";
		String value;

		try {
			DatabaseEntry keyEntry = new DatabaseEntry(key.getBytes("utf-8"));//鍵
			DatabaseEntry valueEntry = new DatabaseEntry();//空的值
			if(database.get(null, keyEntry, valueEntry, LockMode.DEFAULT) == OperationStatus.SUCCESS){//根據鍵來查找
				value = new String(valueEntry.getData(), "utf-8");//找到了對於的值
				System.out.println("key:BaseAPI,value:"+value);
			}
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		}
	}

	//關閉環境
	private void shutDown(){
		database.close();
		env.close();
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		HelloWorldByBaseAPI myCase = new HelloWorldByBaseAPI();
		myCase.setUp();
		myCase.save();
		myCase.get();
		myCase.shutDown();
	}

}