将Berkeley DB基本数据库操作封装成类
江边的山茶
8年前
<p>Berkeley DB是一个嵌入式数据库，适合于管理海量的、简单的数据。</p> <p>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。</p> <p>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：</p> <pre> <code class="language-java">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 Database database; //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-8 chacheSize = 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(); } }</code></pre> <p> </p> <p> </p> <p>来自：http://www.zgljl2012.com/jiang-berkeley-dbji-ben-shu-ju-ku-cao-zuo-feng-zhuang-cheng-lei/</p> <p> </p>