将Berkeley DB基本数据库操作封装成类

Berkeley DB是一个嵌入式数据库，适合于管理海量的、简单的数据。

键值对（key/value）数据存储方式使Berkeley DB用来进行数据库管理的基础，每个key/value构成一条记录。

Berkeley的数据库主要就是put和get，前者存入键值对，后者根据键获取值。

因为Berkeley DB的数据库操作有些复杂，所以将其封装成了一个简单的类：

package ch01_3;import java.io.File;import java.util.AbstractMap.SimpleEntry;import java.util.ArrayList;import java.util.Map.Entry;import com.sleepycat.bind.EntryBinding;import com.sleepycat.bind.serial.SerialBinding;import com.sleepycat.bind.serial.StoredClassCatalog;import com.sleepycat.collections.StoredMap;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.LockMode;import com.sleepycat.je.OperationStatus;/********************************* * 使用BerkeleyDB封装了一些数据库操作 * 包括设置缓冲区，设置编码，设置数据可库 * 路径，存储键值对，根据键查找值，关闭数 * 据库等操作。 * @author Administrator *********************************/public class MyBerkeley {private Environment environment;//环境private Databasedatabase;//数据库@SuppressWarnings("unused")private String charset;//编码private String path;//路径private long        chacheSize;//缓冲区大小private StoredMap<Object, Object> pendingDB = null;private Object keyClass = String.class;//设置默认的key值类型private Object valueClass = Integer.class;//设置默认的value值类型public MyBerkeley(){charset = "UTF-8";//编码默认使用UTF-8chacheSize = 10000;//缓冲区大小默认为10000}//设置编码public void setCharset(String charset){this.charset = charset;}//设置路径public void setPath(String path){//判断Path是否存在File file = new File(path);if(file.mkdir()){System.out.println(path+"已创建！"); //不存在则创建一个}else{System.out.println(path+"已存在！"); //存在则说明已存在}//确定存储路径this.path = path;}//设置缓冲区大小public boolean setChacheSize(long size){if(size<=0 || size >=1000000000){return false; //使用默认的大小}this.chacheSize = size;return true;}//同时设置路径和缓冲区public void setEnvironment(String path , long chacheSize){setPath(path);setChacheSize(chacheSize);//配置环境EnvironmentConfig envConfig = new EnvironmentConfig();envConfig.setAllowCreate(true);envConfig.setCacheSize(this.chacheSize);//创建环境environment = new Environment(new File(this.path),envConfig);}//设置存储类型public void setClassType(Object keyClass,Object valueClass){this.keyClass = keyClass;this.valueClass = valueClass;}//打开名字是dbName的数据库@SuppressWarnings("unchecked")public void open(String dbName){DatabaseConfig dbConfig = new DatabaseConfig();dbConfig.setAllowCreate(true);dbConfig.setSortedDuplicates(false); //不存储重复关键字this.database = environment.openDatabase(null, dbName, dbConfig);//初始化存储序列化对象的catalog类StoredClassCatalog catalog = new StoredClassCatalog(database);//键值都使用序列化的方式进行存储EntryBinding<Object> keyBinding = new SerialBinding<Object>(catalog,(Class<Object>) keyClass);EntryBinding<Object> valueBinding = new SerialBinding<Object>(catalog,(Class<Object>) valueClass);//创建数据存储的映射视图pendingDB = new StoredMap<Object, Object>(database,keyBinding,valueBinding,true);}//关闭public void close(){database.close();environment.close();}//存储public void put(Object key,Object value){pendingDB.put(key, value);}//取值public Object get(Object key){return pendingDB.get(key);}//按照键值删除数据public Object del(Object key){return pendingDB.remove(key);}//获取数据库存储数据的大小public int size(){return pendingDB.size();}//遍历数据库public ArrayList<Entry<Object,Object>> getAllItems(){Cursor cursor = null;//游标ArrayList<Entry<Object,Object>> result = new ArrayList<Entry<Object,Object>>();CursorConfig cConfig = new CursorConfig();if(cursor == null)cursor = database.openCursor(null, cConfig);DatabaseEntry theKey = new DatabaseEntry();DatabaseEntry theValue = new DatabaseEntry();//使用Cursor.getPerv方法来遍历游标获取数据if(cursor.getFirst(theKey, theValue, LockMode.DEFAULT)== OperationStatus.SUCCESS){Object key = theKey.getData();Object value = theValue.getData();Entry<Object,Object> entry = new SimpleEntry<Object,Object>(key,value);result.add(entry);while(cursor.getNext(theKey, theValue, LockMode.DEFAULT)== OperationStatus.SUCCESS){key = theKey.getData();value = theValue.getData();entry = new SimpleEntry<Object,Object>(key,value);result.add(entry);}}cursor.close();//关闭游标return result;}public static void main(String[] args) throws Exception {   MyBerkeley db = new MyBerkeley();   db.setEnvironment("C:\\BerkeleyDB\\MyDatabase2", 1000000);   //设置存储类型（包括键和值）   db.setClassType(String.class, String.class);   db.open("myDB");//打开数据库      //存储值与取值测试   /*   for(int i=10; i>=0; i--) {     String key = "Key"+i;     String value = ""+i;     db.put(key , value);     System.out.println("[" + key + ":" + db.get(key) + "]");   }//*/   //获取数据库键值对数量   System.out.println(db.size());   //删除数据测试   db.del("Key3");   //遍历数据库测试   ArrayList<Entry<Object,Object>> r = db.getAllItems();   for(int i=0;i<r.size();i++)   {   String key = new String((byte[]) r.get(i).getKey());   String value = new String((byte[]) r.get(i).getValue(),"UTF-8");   System.out.println(key+":"+value);   }   db.close();}}