jdbc连接池java_JDBC连接池-自定义连接池

JDBC连接池

java JDBC连接中用到Connection   在每次对数据进行增删查改 都要 开启  、关闭  ，在实例开发项目中 ，浪费了很大的资源 ，以下是之前连接JDBC的案例

packagecom.jdbc.connection;importjava.io.IOException;importjava.io.InputStream;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.PreparedStatement;importjava.sql.ResultSet;importjava.sql.SQLException;importjava.util.Properties;public classjdbcConnection {private staticString driver;private staticString url;private staticString username;private staticString password;/*** 静态代码块加载配置文件信息*/

static{try{//1.通过当前类获取类加载器

ClassLoader classLoader = jdbcConnection.class.getClassLoader();//2.通过类加载器的方法获得一个输入流

InputStream is = classLoader.getResourceAsStream("db.properties");//3.创建一个properties对象

Properties props = newProperties();//4.加载输入流

props.load(is);//5.获取相关参数的值

driver = props.getProperty("driver");

url= props.getProperty("url");

username= props.getProperty("username");

password= props.getProperty("password");

}catch(IOException e) {

e.printStackTrace();

}

}/*** 获取连接方法

**/

public staticConnection getConnection() {

Connection conn= null;try{

Class.forName(driver);

conn=DriverManager.getConnection(url, username, password);

}catch(Exception e) {

e.printStackTrace();

}returnconn;

}/*** 释放资源方法

*

*@paramconn

*@parampstmt

*@paramrs*/

public static voidrelease(Connection conn, PreparedStatement pstmt, ResultSet rs) {if (rs != null) {try{

rs.close();

}catch(SQLException e) {

e.printStackTrace();

}

}if (pstmt != null) {try{

pstmt.close();

}catch(SQLException e) {

e.printStackTrace();

}

}if (conn != null) {try{

conn.close();

}catch(SQLException e) {

e.printStackTrace();

}

}

}

}

考虑节省资源  ，可以创建一个connection连接池 ，每次使用connection连接时 ，直接从连接池中取出一个连接，不用时再放回连接池 ，代替之前的关闭连接  。  java提供了javax.sql.DataSource 接口 ，各大连接池厂商直接实现这个接口

常见的连接池有C3P0  DBCP连接池

自定义连接池

在上面代码的基础上添加一个自定义连接池，减少对资源的浪费

1.创建一个类实现javax.jdbc.dataSource 类

2.创建一个 存放多个连接的容器 ，因为需要经常删除 ，查找  。 这里用LinkedList   容器

3.在MyDataSource类中静态代码块中创建多个连接，添加到连接池容器中  (这里面创建连接可以直接使用 com.jdbc.connection包中的jdbcConnection 中的静态方法getConnection)

1 static{2 for (int i = 0; i < 5; i++) {3 Connection conn=jdbcConnection.getConnection();4

5 }6 }

4.重写Datasource 方法中的 getConnection()  方法    ，

注：在使用pool这个变量之前需要判断pool是否为空 ，若为空需要重新创建

4.在MyDataSource方法中添加  一个 把当前连接归还给连接池的方法

public voidaddBack(Connection conn){

pool.add(conn);

}

具体操作代码如下

packagecom.jdbc.dataSource;importjava.io.PrintWriter;importjava.sql.Connection;importjava.sql.SQLException;importjava.sql.SQLFeatureNotSupportedException;importjava.util.LinkedList;importjava.util.logging.Logger;importjavax.sql.DataSource;importcom.jdbc.connection.jdbcConnection;public class MyDataSource implementsDataSource {private static LinkedList pool=new LinkedList();static{for (int i = 0; i < 5; i++) {

Connection conn=jdbcConnection.getConnection();

pool.add(conn);

}

}

@Overridepublic Connection getConnection() throwsSQLException {

Connection conn=null;if (pool.size()==0) {for (int i = 0; i < 5; i++) {

conn=jdbcConnection.getConnection();

pool.add(conn);

}

}

conn=pool.remove(0);returnconn;

}public voidaddBack(Connection conn){

pool.add(conn);

}

@Overridepublic PrintWriter getLogWriter() throwsSQLException {return null;

}

@Overridepublic int getLoginTimeout() throwsSQLException {//TODO Auto-generated method stub

return 0;

}

@Overridepublic Logger getParentLogger() throwsSQLFeatureNotSupportedException {//TODO Auto-generated method stub

return null;

}

@Overridepublic void setLogWriter(PrintWriter arg0) throwsSQLException {//TODO Auto-generated method stub

}

@Overridepublic void setLoginTimeout(int arg0) throwsSQLException {//TODO Auto-generated method stub

}

@Overridepublic boolean isWrapperFor(Class> arg0) throwsSQLException {//TODO Auto-generated method stub

return false;

}

@Overridepublic T unwrap(Class arg0) throwsSQLException {//TODO Auto-generated method stub

return null;

}

@OverridepublicConnection getConnection(String arg0, String arg1)throwsSQLException {return null;

}

}

连接池测试类

1 packagecom.jdbc.Util;2

3 importjava.sql.Connection;4 importjava.sql.PreparedStatement;5 importjava.sql.SQLException;6

7 importorg.junit.Test;8

9 importcom.jdbc.dataSource.MyDataSource;10

11 public classJdbcTest {12

13 @Test14 public voidtest1(){15 Connection conn=null;16 PreparedStatement pstm=null;17 MyDataSource myDataSource=newMyDataSource();18 try{19 conn=myDataSource.getConnection();20

21 } catch(SQLException e) {22 e.printStackTrace();23 }24

25 }26 }

自定义连接池：方法增强

装饰者模式

创建类B，并实现接口A

提供类B的构造方法，参数类型为A，用于接收A接口的其他实现类(c)

给类B添加类型为A的成员变量，用于存放A接口的其他实现类

增加需要的方法

实现不需要增强的方法，方法体  重点调用成员变量存放的其他实现类对应的方法

翻译过来就是创建类 MyConnection 实现Connection接口

提供MyConnection的构造方法，参数类型为Connection的、  MyDataSource 类中的连接池对象list

。。。等

1 packagecom.jdbc.dataSource;2

3 importjava.sql.Array;4 importjava.sql.Blob;5 importjava.sql.CallableStatement;6 importjava.sql.Clob;7 importjava.sql.Connection;8 importjava.sql.DatabaseMetaData;9 importjava.sql.NClob;10 importjava.sql.PreparedStatement;11 importjava.sql.SQLClientInfoException;12 importjava.sql.SQLException;13 importjava.sql.SQLWarning;14 importjava.sql.SQLXML;15 importjava.sql.Savepoint;16 importjava.sql.Statement;17 importjava.sql.Struct;18 importjava.util.LinkedList;19 importjava.util.Map;20 importjava.util.Properties;21 importjava.util.concurrent.Executor;22

23 public class MyConnection implementsConnection {24 privateConnection conn;25 private LinkedListpool;26 public MyConnection(Connection conn ,LinkedListpool) {27 this.pool=pool;28 this.conn =conn;29 }30 @Override31 public void close() throwsSQLException {32 pool.add(conn);33 }34 @Override35 public boolean isWrapperFor(Class> arg0) throwsSQLException {36 //TODO Auto-generated method stub

37 return false;38 }39

40 @Override41 public T unwrap(Class arg0) throwsSQLException {42 //TODO Auto-generated method stub

43 return null;44 }45

46 @Override47 public void abort(Executor executor) throwsSQLException {48 //TODO Auto-generated method stub

49

50 }51

52 @Override53 public void clearWarnings() throwsSQLException {54 //TODO Auto-generated method stub

55

56 }57

58

59

60 @Override61 public void commit() throwsSQLException {62 //TODO Auto-generated method stub

63

64 }65

66 @Override67 publicArray createArrayOf(String typeName, Object[] elements)68 throwsSQLException {69 //TODO Auto-generated method stub

70 return null;71 }72

73 @Override74 public Blob createBlob() throwsSQLException {75 //TODO Auto-generated method stub

76 return null;77 }78

79 @Override80 public Clob createClob() throwsSQLException {81 //TODO Auto-generated method stub

82 return null;83 }84

85 @Override86 public NClob createNClob() throwsSQLException {87 //TODO Auto-generated method stub

88 return null;89 }90

91 @Override92 public SQLXML createSQLXML() throwsSQLException {93 //TODO Auto-generated method stub

94 return null;95 }96

97 @Override98 public Statement createStatement() throwsSQLException {99 //TODO Auto-generated method stub

100 return null;101 }102

103 @Override104 public Statement createStatement(int resultSetType, intresultSetConcurrency)105 throwsSQLException {106 //TODO Auto-generated method stub

107 return null;108 }109

110 @Override111 public Statement createStatement(intresultSetType,112 int resultSetConcurrency, intresultSetHoldability)113 throwsSQLException {114 //TODO Auto-generated method stub

115 return null;116 }117

118 @Override119 publicStruct createStruct(String typeName, Object[] attributes)120 throwsSQLException {121 //TODO Auto-generated method stub

122 return null;123 }124

125 @Override126 public boolean getAutoCommit() throwsSQLException {127 //TODO Auto-generated method stub

128 return false;129 }130

131 @Override132 public String getCatalog() throwsSQLException {133 //TODO Auto-generated method stub

134 return null;135 }136

137 @Override138 public Properties getClientInfo() throwsSQLException {139 //TODO Auto-generated method stub

140 return null;141 }142

143 @Override144 public String getClientInfo(String name) throwsSQLException {145 //TODO Auto-generated method stub

146 return null;147 }148

149 @Override150 public int getHoldability() throwsSQLException {151 //TODO Auto-generated method stub

152 return 0;153 }154

155 @Override156 public DatabaseMetaData getMetaData() throwsSQLException {157 //TODO Auto-generated method stub

158 return null;159 }160

161 @Override162 public int getNetworkTimeout() throwsSQLException {163 //TODO Auto-generated method stub

164 return 0;165 }166

167 @Override168 public String getSchema() throwsSQLException {169 //TODO Auto-generated method stub

170 return null;171 }172

173 @Override174 public int getTransactionIsolation() throwsSQLException {175 //TODO Auto-generated method stub

176 return 0;177 }178

179 @Override180 public Map> getTypeMap() throwsSQLException {181 //TODO Auto-generated method stub

182 return null;183 }184

185 @Override186 public SQLWarning getWarnings() throwsSQLException {187 //TODO Auto-generated method stub

188 return null;189 }190

191 @Override192 public boolean isClosed() throwsSQLException {193 //TODO Auto-generated method stub

194 return false;195 }196

197 @Override198 public boolean isReadOnly() throwsSQLException {199 //TODO Auto-generated method stub

200 return false;201 }202

203 @Override204 public boolean isValid(int timeout) throwsSQLException {205 //TODO Auto-generated method stub

206 return false;207 }208

209 @Override210 public String nativeSQL(String sql) throwsSQLException {211 //TODO Auto-generated method stub

212 return null;213 }214

215 @Override216 public CallableStatement prepareCall(String sql) throwsSQLException {217 //TODO Auto-generated method stub

218 return null;219 }220

221 @Override222 public CallableStatement prepareCall(String sql, intresultSetType,223 int resultSetConcurrency) throwsSQLException {224 //TODO Auto-generated method stub

225 return null;226 }227

228 @Override229 public CallableStatement prepareCall(String sql, intresultSetType,230 int resultSetConcurrency, intresultSetHoldability)231 throwsSQLException {232 //TODO Auto-generated method stub

233 return null;234 }235

236 @Override237 public PreparedStatement prepareStatement(String sql) throwsSQLException {238 //TODO Auto-generated method stub

239 return null;240 }241

242 @Override243 public PreparedStatement prepareStatement(String sql, intautoGeneratedKeys)244 throwsSQLException {245 //TODO Auto-generated method stub

246 return null;247 }248

249 @Override250 public PreparedStatement prepareStatement(String sql, int[] columnIndexes)251 throwsSQLException {252 //TODO Auto-generated method stub

253 return null;254 }255

256 @Override257 publicPreparedStatement prepareStatement(String sql, String[] columnNames)258 throwsSQLException {259 //TODO Auto-generated method stub

260 return null;261 }262

263 @Override264 public PreparedStatement prepareStatement(String sql, intresultSetType,265 int resultSetConcurrency) throwsSQLException {266 //TODO Auto-generated method stub

267 return null;268 }269

270 @Override271 public PreparedStatement prepareStatement(String sql, intresultSetType,272 int resultSetConcurrency, intresultSetHoldability)273 throwsSQLException {274 //TODO Auto-generated method stub

275 return null;276 }277

278 @Override279 public void releaseSavepoint(Savepoint savepoint) throwsSQLException {280 //TODO Auto-generated method stub

281

282 }283

284 @Override285 public void rollback() throwsSQLException {286 //TODO Auto-generated method stub

287

288 }289

290 @Override291 public void rollback(Savepoint savepoint) throwsSQLException {292 //TODO Auto-generated method stub

293

294 }295

296 @Override297 public void setAutoCommit(boolean autoCommit) throwsSQLException {298 //TODO Auto-generated method stub

299

300 }301

302 @Override303 public void setCatalog(String catalog) throwsSQLException {304 //TODO Auto-generated method stub

305

306 }307

308 @Override309 public voidsetClientInfo(Properties properties)310 throwsSQLClientInfoException {311 //TODO Auto-generated method stub

312

313 }314

315 @Override316 public voidsetClientInfo(String name, String value)317 throwsSQLClientInfoException {318 //TODO Auto-generated method stub

319

320 }321

322 @Override323 public void setHoldability(int holdability) throwsSQLException {324 //TODO Auto-generated method stub

325

326 }327

328 @Override329 public void setNetworkTimeout(Executor executor, intmilliseconds)330 throwsSQLException {331 //TODO Auto-generated method stub

332

333 }334

335 @Override336 public void setReadOnly(boolean readOnly) throwsSQLException {337 //TODO Auto-generated method stub

338

339 }340

341 @Override342 public Savepoint setSavepoint() throwsSQLException {343 //TODO Auto-generated method stub

344 return null;345 }346

347 @Override348 public Savepoint setSavepoint(String name) throwsSQLException {349 //TODO Auto-generated method stub

350 return null;351 }352

353 @Override354 public void setSchema(String schema) throwsSQLException {355 //TODO Auto-generated method stub

356

357 }358

359 @Override360 public void setTransactionIsolation(int level) throwsSQLException {361 //TODO Auto-generated method stub

362

363 }364

365 @Override366 public void setTypeMap(Map> map) throwsSQLException {367 //TODO Auto-generated method stub

368

369 }370

371

372 }

更改后的myDataSource类为

1 packagecom.jdbc.dataSource;2

3 importjava.io.PrintWriter;4 importjava.sql.Connection;5 importjava.sql.SQLException;6 importjava.sql.SQLFeatureNotSupportedException;7 importjava.util.LinkedList;8 importjava.util.logging.Logger;9

10 importjavax.sql.DataSource;11

12 importcom.jdbc.connection.jdbcConnection;13

14 public class MyDataSource1 implementsDataSource{15 private static LinkedList pool=new LinkedList();16 static{17 for (int i = 0; i < 5; i++) {18 Connection conn=jdbcConnection.getConnection();19 pool.add(conn);20 }21 }22 @Override23 public Connection getConnection() throwsSQLException {24 if (pool.size()==0) {25 for (int i = 0; i < 5; i++) {26 Connection conn=jdbcConnection.getConnection();27 //MyConnection 类实现了Connection接口28 //将创建的连接用装饰者类包装

29 MyConnection myConnection=newMyConnection(conn, pool);30 //pool.add(conn);

31 pool.add(myConnection);//添加被装饰后的connection对象

32 }33 }34 Connection conn=pool.remove(0);35 returnconn;36 }37

38 @Override39 public PrintWriter getLogWriter() throwsSQLException {40

41 return null;42 }43

44 @Override45 public int getLoginTimeout() throwsSQLException {46 //TODO Auto-generated method stub

47 return 0;48 }49

50 @Override51 public Logger getParentLogger() throwsSQLFeatureNotSupportedException {52 //TODO Auto-generated method stub

53 return null;54 }55

56 @Override57 public void setLogWriter(PrintWriter arg0) throwsSQLException {58 //TODO Auto-generated method stub

59

60 }61

62 @Override63 public void setLoginTimeout(int arg0) throwsSQLException {64 //TODO Auto-generated method stub

65

66 }67

68 @Override69 public boolean isWrapperFor(Class> iface) throwsSQLException {70 //TODO Auto-generated method stub

71 return false;72 }73

74 @Override75 public T unwrap(Class iface) throwsSQLException {76 //TODO Auto-generated method stub

77 return null;78 }79

80

81

82 @Override83 publicConnection getConnection(String username, String password)84 throwsSQLException {85 //TODO Auto-generated method stub

86 return null;87 }88

89

90

91 }

测试

packagecom.study.jdbc.test;importjava.sql.Connection;importjava.sql.PreparedStatement;importjava.sql.SQLException;importorg.junit.Test;importcom.study.jdbc.Utils.JDBCUtils_V3;importcom.study.jdbc.dataSource.MyDataSource;importcom.study.jdbc.dataSource.MyDataSource1;public classTestMyDataSource {/** 添加用户

* 使用改造过的connection

**/@Testpublic voiddataTestAddUser1(){

Connection conn=null;

PreparedStatement pstm=null;

MyDataSource1 dataSource=newMyDataSource1();try{

conn=dataSource.getConnection();

System.out.println(conn);

String sql="insert into user values(10,?,?)";

pstm=conn.prepareStatement(sql);

pstm.setString(1,"吕布1");

pstm.setString(2,"点错1");int rows =pstm.executeUpdate();if (rows>0) {

System.out.println("ok");

}else{

System.out.println("no");

}

}catch(SQLException e) {

e.printStackTrace();

}finally{//release中conn.close()方法已经被装饰

JDBCUtils_V3.release(conn, pstm, null);

}

}

}

需要注意的是：MyConection 实现Connection接口时重新了Connection所有的方法，在使用 被MyConnection类修饰的Connecting连接的某些方法要注意需要重写MyConnection类中的这些方法

比如：当使用prepareStatement(sql); 时  要注意MyConnection中的prepareStatement(String sql)方法

MyConnection 在未处理之前的prepareStatement(String sql)方法如下图所示

不重写直接使用 返回的结果永远是null  ，重写后代码：

1 @Override2 public PreparedStatement prepareStatement(String sql) throwsSQLException {3 //TODO Auto-generated method stub

4 returnconn.prepareStatement(sql);5 }