code

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<String> 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<String> resultList = new ArrayList<String>();
        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();
        }
    }
}