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import java.io.File;import java.io.UnsupportedEncodingException;import java.util.ArrayList;import com.sleepycat.je.Cursor;import com.sleepycat.je.CursorConfig;import com.sleepycat.je.Database;import com.sleepycat.je.DatabaseConfig;import com.sleepycat.je.DatabaseEntry;import com.sleepycat.je.Environment;import com.sleepycat.je.EnvironmentConfig;import com.sleepycat.je.LockConflictException;import com.sleepycat.je.LockMode;import com.sleepycat.je.OperationStatus;import com.sleepycat.je.Transaction;import com.sleepycat.je.TransactionConfig;public class BDB {	// 数据库环境	private Environment env = null;	// 数据库	private final Database frontierDatabase;	// 数据库名	private final String dbName;	public BDB(String homeDirectory,String dbName) {		// 1、创建EnvironmentConfig		EnvironmentConfig envConfig = new EnvironmentConfig();		envConfig.setTransactional(false);		envConfig.setAllowCreate(true);		// 2、使用EnvironmentConfig配置Environment		env = new Environment(new File(homeDirectory), envConfig);		// 3、创建DatabaseConfig		DatabaseConfig dbConfig = new DatabaseConfig();		dbConfig.setTransactional(false);		dbConfig.setAllowCreate(true);		// 4、使用Environment与DatabaseConfig打开Database		frontierDatabase = env.openDatabase(null, dbName, dbConfig);		this.dbName = dbName;	}	/*	 * 向数据库中写入记录，并判断是否可以有重复数据。 传入key和value	 * 若可以有重复数据，则直接使用put()即可，若不能有重复数据，则使用putNoOverwrite()。	 */	public boolean writeToDatabase(String key, String value, boolean isOverwrite) {		try {			// 设置key/value,注意DatabaseEntry内使用的是bytes数组			DatabaseEntry theKey = new DatabaseEntry(key.getBytes("UTF-8"));			DatabaseEntry theData = new DatabaseEntry(value.getBytes("UTF-8"));			OperationStatus status = null;			Transaction txn = null;			try {				// 1、Transaction配置				TransactionConfig txConfig = new TransactionConfig();				txConfig.setSerializableIsolation(true);				txn = env.beginTransaction(null, txConfig);				// 2、写入数据				if (isOverwrite) {					status = frontierDatabase.put(txn, theKey, theData);				} else {					status = frontierDatabase.putNoOverwrite(txn, theKey, theData);				}				txn.commit();				if (status == OperationStatus.SUCCESS) {//					System.out.println("向数据库" + dbName + "中写入:" + key + "," + value);					return true;				} else if (status == OperationStatus.KEYEXIST) {//					System.out.println("向数据库" + dbName + "中写入:" + key + "," + value + "失败,该值已经存在");					return false;				} else {//					System.out.println("向数据库" + dbName + "中写入:" + key + "," + value + "失败");					return false;				}			} catch (LockConflictException lockConflict) {				txn.abort();				System.out.println("向数据库" + dbName + "中写入:" + key + "," + value + "出现lock异常");				return false;			}		} catch (Exception e) {			// 错误处理			System.out.println("向数据库" + dbName + "中写入:" + key + "," + value + "出现错误");			return false;		}	}	/*	 * 从数据库中读出数据 传入key 返回value	 */	public String readFromDatabase(String key) {		try {			DatabaseEntry theKey = new DatabaseEntry(key.getBytes("UTF-8"));			DatabaseEntry theData = new DatabaseEntry();			Transaction txn = null;			try {				// 1、配置 Transaction相关信息				TransactionConfig txConfig = new TransactionConfig();				txConfig.setSerializableIsolation(true);				txn = env.beginTransaction(null, txConfig);				// 2、读取数据				OperationStatus status = frontierDatabase.get(txn, theKey, theData, LockMode.DEFAULT);				txn.commit();				if (status == OperationStatus.SUCCESS) {					// 3、将字节转换成String					byte[] retData = theData.getData();					String value = new String(retData, "UTF-8");					System.out.println("从数据库" + dbName + "中读取:" + key + "," + value);					return value;				} else {					System.out.println("No record found for key '" + key + "'.");					return "";				}			} catch (LockConflictException lockConflict) {				txn.abort();				System.out.println("从数据库" + dbName + "中读取:" + key + "出现lock异常");				return "";			}		} catch (UnsupportedEncodingException e) {			e.printStackTrace();			return "";		}	}	/*	 * 遍历数据库中的所有记录，返回list	 */	public ArrayList
    
      getEveryItem() {		// TODO Auto-generated method stub		System.out.println("===========遍历数据库" + dbName + "中的所有数据==========");		Cursor myCursor = null;		ArrayList
     
       resultList = new ArrayList
      
       ();		Transaction txn = null;		try {			txn = this.env.beginTransaction(null, null);			CursorConfig cc = new CursorConfig();			cc.setReadCommitted(true);			if (myCursor == null)				myCursor = frontierDatabase.openCursor(txn, cc);			DatabaseEntry foundKey = new DatabaseEntry();			DatabaseEntry foundData = new DatabaseEntry();			// 使用cursor.getPrev方法来遍历游标获取数据			if (myCursor.getFirst(foundKey, foundData, LockMode.DEFAULT) == OperationStatus.SUCCESS) {				String theKey = new String(foundKey.getData(), "UTF-8");				String theData = new String(foundData.getData(), "UTF-8");				resultList.add(theKey);				System.out.println("Key | Data : " + theKey + " | " + theData + "");				while (myCursor.getNext(foundKey, foundData, LockMode.DEFAULT) == OperationStatus.SUCCESS) {					theKey = new String(foundKey.getData(), "UTF-8");					theData = new String(foundData.getData(), "UTF-8");					resultList.add(theKey);					System.out.println("Key | Data : " + theKey + " | " + theData + "");				}			}			myCursor.close();			txn.commit();			return resultList;		} catch (UnsupportedEncodingException e) {			e.printStackTrace();			return null;		} catch (Exception e) {			System.out.println("getEveryItem处理出现异常");			txn.abort();			if (myCursor != null) {				myCursor.close();			}			return null;		}	}	/*	 * 根据key值删除数据库中的一条记录	 */	public boolean deleteFromDatabase(String key) {		boolean success = false;		long sleepMillis = 0;		for (int i = 0; i < 3; i++) {			if (sleepMillis != 0) {				try {					Thread.sleep(sleepMillis);				} catch (InterruptedException e) {					e.printStackTrace();				}				sleepMillis = 0;			}			Transaction txn = null;			try {				// 1、使用cursor.getPrev方法来遍历游标获取数据				TransactionConfig txConfig = new TransactionConfig();				txConfig.setSerializableIsolation(true);				txn = env.beginTransaction(null, txConfig);				DatabaseEntry theKey;				theKey = new DatabaseEntry(key.getBytes("UTF-8"));				// 2、删除数据 并提交				OperationStatus res = frontierDatabase.delete(txn, theKey);				txn.commit();				if (res == OperationStatus.SUCCESS) {					System.out.println("从数据库" + dbName + "中删除:" + key);					success = true;					return success;				} else if (res == OperationStatus.KEYEMPTY) {					System.out.println("没有从数据库" + dbName + "中找到:" + key + "。无法删除");				} else {					System.out.println("删除操作失败，由于" + res.toString());				}				return false;			} catch (UnsupportedEncodingException e) {				e.printStackTrace();				return false;			} catch (LockConflictException lockConflict) {				System.out.println("删除操作失败，出现lockConflict异常");				sleepMillis = 1000;				continue;			} finally {				if (!success) {					if (txn != null) {						txn.abort();					}				}			}		}		return false;	}	public void closeDB() {		if (frontierDatabase != null) {			frontierDatabase.close();		}		if (env != null) {			env.close();		}	}}