Java嵌入式NoSQL数据库之Berkeley DB Java Edition

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一个通用的事务保护，100％纯Java编写的嵌入式NoSQL数据库，采取开源（免费）和商用（付费）的双License的授权模式。Berkeley DB是历史悠久的嵌入式数据库系统，06年被 Oracle 收购，而Berkeley DB Java Edition是Berkeley DB产品中的一部分。

引用

Berkeley DB Java Edition is a open source, transactional storage solution for Java applications. The Direct Persistence Layer (DPL) API is faster and easier to develop, deploy, and manage than serialized object files or ORM-based Java persistence solutions.  The Collections API enhances the standard java.util.collections classes allowing them to be persisted to a local file system and accessed concurrently while protected by ACID transactions. Data is stored by serializing objects and managing class and instance data separately so as not to waste space. Berkeley DB Java Edition is the reliable drop-in solution for complex, fast, and scalable storage.

http://www.oracle.com/technetwork/products/berkeleydb/downloads/index.html

版本：Berkeley DB Java Edition 5.0.73.zip

（1）打开Database环境

EnvironmentConfig envCfg = new EnvironmentConfig();
//当数据库环境不存在的时候，创建一个数据库环境，默认为false.
envCfg.setAllowCreate(true);
//以只读方式打开，默认为false.
envCfg.setReadOnly(false);
//事务支持，默认为false.
envCfg.setTransactional(true);

Environment mydbEnv = new Environment(new File(envHome), envCfg);

System.out.println("Env Config: " + mydbEnv.getConfig());

（2）打开Database

DatabaseConfig dbCfg = new DatabaseConfig();
dbCfg.setAllowCreate(true);
dbCfg.setReadOnly(false);
dbCfg.setTransactional(true);

Database mytestdb = mydbEnv.openDatabase(null, "VendorDB", dbCfg);
	
System.out.println("Database Name: " + mytestdb.getDatabaseName());

（3）简单的CRUD

//C
String key = "key-rensanning";
String value = "This is a test!(000)";

DatabaseEntry keyEntry = new DatabaseEntry(key.getBytes("utf-8"));
DatabaseEntry valEntry = new DatabaseEntry(value.getBytes("utf-8"));
OperationStatus status = mytestdb.put(null, keyEntry, valEntry);
System.out.println("Put Status: " + status);

//R
DatabaseEntry valGet = new DatabaseEntry();
status = mytestdb.get(null, keyEntry, valGet, LockMode.DEFAULT);
if (status == OperationStatus.SUCCESS) {
	value = new String(valGet.getData(), "utf-8");
	System.out.println("Read Value:" + value);
}

//U
value = "This is a test!(111)";
status = mytestdb.put(null, keyEntry, new DatabaseEntry(value.getBytes("utf-8")));

status = mytestdb.get(null, keyEntry, valGet, LockMode.DEFAULT);
if (status == OperationStatus.SUCCESS) {
	value = new String(valGet.getData(), "utf-8");
	System.out.println("Update Value:" + value);
}

//D
status = mytestdb.delete(null, keyEntry);
System.out.println("Delete Status: " + status);

（4）不同的数据写入方式

String key = "key-rensanning";
DatabaseEntry keyEntry = new DatabaseEntry(key.getBytes("utf-8"));
DatabaseEntry valGet = new DatabaseEntry();

String value = "This is a test!(by 'put' method)";
//Database.put()： 向数据库写入数据，如果不支持重复记录，则会覆盖更新key对应的已有记录
OperationStatus status = mytestdb.put(null, keyEntry, new DatabaseEntry(value.getBytes("utf-8")));

status = mytestdb.get(null, keyEntry, valGet, LockMode.DEFAULT);
if (status == OperationStatus.SUCCESS) {
	value = new String(valGet.getData(), "utf-8");
	System.out.println("Put Value:" + value);
}

//Database.putNoOverwrite():向数据库写入数据，但是如果key已经存在，不会覆盖已有数据（即使数据库支持重复key）
value = "This is a test!(by 'putNoOverwrite' method)";
status = mytestdb.putNoOverwrite(null, keyEntry, new DatabaseEntry(value.getBytes("utf-8")));

status = mytestdb.get(null, keyEntry, valGet, LockMode.DEFAULT);
if (status == OperationStatus.SUCCESS) {
	value = new String(valGet.getData(), "utf-8");
	System.out.println("PutNoOverwrite Value:" + value);
}

//*****设置一个key是否允许存储多个值*****
DatabaseConfig dbCfg = new DatabaseConfig();
dbCfg.setAllowCreate(true);
dbCfg.setReadOnly(false);
dbCfg.setTransactional(true);
dbCfg.setSortedDuplicates(true);

Database mytestdb2 = mytestdb.getEnvironment().openDatabase(null, "DuplicatesDB", dbCfg);

//Database.putNoDupData():向数据库写入数据（该方法仅用于支持重复key的数据库），如果key和value对应的记录已经存在，那么操作结果是：OperationStatus.KEYEXIST
value = "This is a test!(by 'putNoDupData' method)";
status = mytestdb2.putNoDupData(null, keyEntry, new DatabaseEntry(value.getBytes("utf-8")));
if (status == OperationStatus.SUCCESS) {
	value = new String(valGet.getData(), "utf-8");
	System.out.println("PutNoOverwrite Value:" + value);
} else if (status == OperationStatus.KEYEXIST) {
	System.out.println("putNoDupData KEYEXIST:" + key);
}

status = mytestdb2.get(null, keyEntry, valGet, LockMode.DEFAULT);
if (status == OperationStatus.SUCCESS) {
	value = new String(valGet.getData(), "utf-8");
	System.out.println("putNoDupData Value:" + value);
}

if (null != mytestdb2) {
	mytestdb2.close();
	mytestdb2 = null;
}

（5）不同的数据读取方式

String key = "key-rensanning";
String value = "This is a test!(000)";
DatabaseEntry keyEntry = new DatabaseEntry(key.getBytes("utf-8"));
DatabaseEntry valEntry = new DatabaseEntry(value.getBytes("utf-8"));
OperationStatus status = mytestdb.put(null, keyEntry, valEntry);
System.out.println("Put Status: " + status);

DatabaseEntry valGet = new DatabaseEntry();

//Database.get() ：检索key对应的记录
status = mytestdb.get(null, keyEntry, valGet, LockMode.DEFAULT);
if (status == OperationStatus.SUCCESS) {
	value = new String(valGet.getData(), "utf-8");
	System.out.println("Read Value(get):" + value);
}

//Database.getSearchBoth() ：根据key和value 检索数据库记录
status = mytestdb.getSearchBoth(null, keyEntry, valGet, LockMode.DEFAULT);
if (status == OperationStatus.SUCCESS) {
	value = new String(valGet.getData(), "utf-8");
	System.out.println("Read Value(getSearchBoth):" + value);
}

（6）对象的读写

//C
String key = "key-rensanning-Object";
Person value = new Person(9527, "rensanning", true);

DatabaseEntry keyEntry = new DatabaseEntry(key.getBytes("utf-8"));
DatabaseEntry valEntry = new DatabaseEntry();
PersonTupleBinding personBinding = new PersonTupleBinding();
personBinding.objectToEntry(value, valEntry);

OperationStatus status = mytestdb.put(null, keyEntry, valEntry);
System.out.println("Put Person Status: " + status);

//R
DatabaseEntry valGet = new DatabaseEntry();
status = mytestdb.get(null, keyEntry, valGet, LockMode.DEFAULT);
if (status == OperationStatus.SUCCESS) {
	value = personBinding.entryToObject(valGet);
	System.out.println("Read Person Value:" + value.getId() + "\t" + value.getName() + "\t" + value.isSex());
}

class Person {
	int id;
	String name;
	boolean sex;

	public Person() {
	}
	
	public Person(int id, String name, boolean sex) {
		this.id = id;
		this.name = name;
		this.sex = sex;
	}
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public boolean isSex() {
		return sex;
	}
	public void setSex(boolean sex) {
		this.sex = sex;
	}
}

class PersonTupleBinding extends TupleBinding {

	@Override
	public Person entryToObject(TupleInput input) {
		Person p = new Person();
		p.setId(input.readInt());
		p.setName(input.readString());
		p.setSex(input.readBoolean());
		return p;
	}

	@Override
	public void objectToEntry(Person p, TupleOutput output) {		
		output.writeInt(p.getId());
		output.writeString(p.getName());
		output.writeBoolean(p.isSex());
	}
}

（7）直接持久层应用（DPL：Direct Persistence Layer）

Environment env = mytestdb.getEnvironment();

StoreConfig storeConfig = new StoreConfig();
storeConfig.setAllowCreate(true);
storeConfig.setTransactional(true);

EntityStore store = new EntityStore(env, "StoreDB", storeConfig);

PrimaryIndex pIndex = store.getPrimaryIndex(String.class, UserInfo.class);

//C
pIndex.put(new UserInfo("001", "user001"));
pIndex.put(new UserInfo("002", "user002"));
pIndex.put(new UserInfo("003", "user003"));
pIndex.put(new UserInfo("004", "user004"));
pIndex.put(new UserInfo("005", "user005"));

//R
String myKey = "001";
UserInfo getData = pIndex.get(myKey);
System.out.println("Read User 001:" + getData);

//U
pIndex.put(new UserInfo("002", "user002222"));

//Read ALL
EntityCursor cursor = pIndex.entities();
try {
	Iterator i = cursor.iterator();
	while (i.hasNext()) {
		System.out.println("Cursor data:" + i.next());
	}
} finally {
	cursor.close();
}

//D
String pkey = "003";
boolean flag = pIndex.delete(pkey);
System.out.println("delete object :" + pkey + " result:" + flag);

//关闭store
if (store != null) {
	store.close();
	store = null;
}

@Entity
@SuppressWarnings("serial")
class UserInfo implements Serializable {
	
	@PrimaryKey
	private String userId;
	private String userName;

	public UserInfo() {
	}

	public UserInfo(String userId, String userName) {
		this.userId = userId;
		this.userName = userName;
	}

	public String getUserId() {
		return userId;
	}
	public void setUserId(String userId) {
		this.userId = userId;
	}
	public String getUserName() {
		return userName;
	}
	public void setUserName(String userName) {
		this.userName = userName;
	}

	@Override
	public String toString() {
		return "UserInfo [userId=" + userId + ", userName=" + userName + "]";
	}
}

（8）事务处理

Transaction txn = mytestdb.getEnvironment().beginTransaction(null, null);
try {
	for(int i = 0; i < 5; i++) {
		mytestdb.put(txn, new DatabaseEntry(("TXN-KEY"+(i+1)).getBytes("utf-8")), new DatabaseEntry(("TXN-VALUE"+(i+1)).getBytes("utf-8")));
	}
} catch (DatabaseException e) {
	if (txn != null) {
		txn.abort();
		txn = null;
	}
	throw e;
} finally {
	if (txn != null) {
		txn.commit();
	}
}

（9）游标操作

//C
for(int i = 0; i < 5; i++) {
	mytestdb.put(null, new DatabaseEntry(("KEY"+(i+1)).getBytes("utf-8")), new DatabaseEntry(("VALUE"+(i+1)).getBytes("utf-8")));
}

DatabaseEntry key = new DatabaseEntry();
DatabaseEntry value = new DatabaseEntry();

//D (by Cursor)
Transaction txn = mytestdb.getEnvironment().beginTransaction(null, null);
Cursor cursor1 = mytestdb.openCursor(txn, null);
OperationStatus result1 = cursor1.getFirst(key, value, null);
while (result1 == OperationStatus.SUCCESS) {
	if ("VALUE3".equals(new String(value.getData(), "utf-8"))) {
		cursor1.delete();
	}		
	result1 = cursor1.getNext(key, value, null);
}

if (cursor1 != null) {
	cursor1.close();
}
if (txn != null) {
	txn.commit();
}

//R (by Cursor)
Cursor cursor2 = mytestdb.openCursor(null, null);
OperationStatus result2 = cursor2.getFirst(key, value, null);

while (result2 == OperationStatus.SUCCESS) {
	System.out.println("Cursor Read Value:" + new String(value.getData(), "utf-8"));			
	result2 = cursor2.getNext(key, value, null);
}

if (cursor2 != null) {
	cursor2.close();
}

（10）关闭database

//关闭database
if (mytestdb != null) {
	mytestdb.close();
	mytestdb = null;
}

（11）关闭database环境

//关闭database环境
if (mydbEnv != null) {
	mydbEnv.sync();//把数据同步到磁盘中去
	mydbEnv.cleanLog();//清理日志
	mydbEnv.close();
	mydbEnv = null;
}

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