连接池概述:
管理数据库的连接,
作用:
提高项目的性能.
就是在连接池初始化的时候存入一定数量的连接,用的时候通过方法获取,不用的时候归还连接即可.
所有的连接池必须实现一个接口 javax.sql.DataSource接口
获取连接方法:
Connection getConnection()
归还连接的方法就是以前的释放资源的方法.调用connection.close();
增强方法:
1.继承
2.装饰者模式(静态代理)
3.动态代理
装饰者模式:
使用步骤:
1.装饰者和被装饰者实现同一个接口或者继承同一个类
2.装饰者中要有被装饰者的引用
3.对需要增强的方法进行加强
4.对不需要加强的方法调用原来方法
思路:把自定义的连接池close方法增强为放入连接池中
a.先自定义一个连接池
1.先创建一个LinkedList集合（增删快，查询慢）作为连接池
2.再在静态代码块中初始化连接池个数（3个）
3.创建一个getConnection方法，判断连接池是否为空，然后执行下面操作
1 package cn.jdbc_myConn;
2
3 import java.sql.Connection;
4 import java.util.LinkedList;
5
6 import cn.jdbc_utils.JdbcUtils;
7
8 public class MyDataSource {
9 // 用LinkedList 增删快 查询慢
10 static LinkedList<Connection> pool = new LinkedList<>();
11 static {
12 // 初始化的时候需要放入3个连接,存放对象则是集合
13 for (int i = 0; i < 3; i++) {
14 try {
15 Connection conn = JdbcUtils.getConnection();
16 pool.addLast(conn);
17 } catch (Exception e) {
18 e.printStackTrace();
19 }
20 }
21 }
22
23 // 获取连接
24 public static Connection getConnection() {
25 if (pool.isEmpty()) {
26 for (int i = 0; i < 3; i++) {
27 try {
28 Connection conn = JdbcUtils.getConnection();
29 pool.addLast(conn);
30 } catch (Exception e) {
31 e.printStackTrace();
32 }
33 }
34 }
35 return pool.removeFirst();//先进先出
36 }
37 // 归还连接的方法用装饰者模式增强
38 }
使用装饰者模式增强close方法
1.创建一个MyConn类，实现Connection接口（java.sql）
2.需要增强的close方法则重写
3.不需要增强的方法调用原方法
自定义连接池类
1 package cn.jdbc_myConn;
2
3 import java.sql.Connection;
4 import java.util.LinkedList;
5
6 import cn.jdbc_utils.JdbcUtils;
7
8 public class MyDataSource {
9 // 用LinkedList 增删快 查询慢
10 static LinkedList<Connection> pool = new LinkedList<>();
11 static {
12 // 初始化的时候需要放入3个连接,存放对象则是集合
13 for (int i = 0; i < 3; i++) {
14 try {
15 Connection conn = JdbcUtils.getConnection();
16 pool.addLast(conn);
17 } catch (Exception e) {
18 e.printStackTrace();
19 }
20 }
21 }
22
23 // 获取连接
24 public static Connection getConnection() {
25 if (pool.isEmpty()) {
26 for (int i = 0; i < 3; i++) {
27 try {
28 Connection conn = JdbcUtils.getConnection();
29 pool.addLast(conn);
30 } catch (Exception e) {
31 e.printStackTrace();
32 }
33 }
34 }
35 System.out.println("从池子中获取了一个连接");
36 Connection conn = pool.removeFirst();
37 MyConnWarp myConn = new MyConnWarp(conn,pool);
38 return myConn;//先进先出
39 }
40 // 归还连接的方法用装饰着模式增强
41 }
重写close方法类
1 package cn.jdbc_myConn;
2
3 import java.sql.Array;
4 import java.sql.Blob;
5 import java.sql.CallableStatement;
6 import java.sql.Clob;
7 import java.sql.Connection;
8 import java.sql.DatabaseMetaData;
9 import java.sql.NClob;
10 import java.sql.PreparedStatement;
11 import java.sql.SQLClientInfoException;
12 import java.sql.SQLException;
13 import java.sql.SQLWarning;
14 import java.sql.SQLXML;
15 import java.sql.Savepoint;
16 import java.sql.Statement;
17 import java.sql.Struct;
18 import java.util.LinkedList;
19 import java.util.Map;
20 import java.util.Properties;
21 import java.util.concurrent.Executor;
22
23 public class MyConnWarp implements Connection {
24
25 private Connection conn;
26 private LinkedList<Connection> list;
27 //带参构造,传入connection,语句执行者,获取连接需要连接池
28 public MyConnWarp(Connection conn){
29 this.conn=conn;
30 }
31 public MyConnWarp(Connection conn,LinkedList<Connection> list){
32 this.conn=conn;
33 this.list=list;
34 }
35 //需要加强的方法
36 @Override
37 public void close() throws SQLException {
38 //添加到连接池中
39 System.out.println("归还前的大小："+list.size());
40 list.addFirst(this);
41 System.out.println("归还后的大小："+list.size());
42 System.out.println("已经归还!");
43 }
44
45 @Override
46 public Statement createStatement() throws SQLException {
47 // TODO Auto-generated method stub
48 return conn.createStatement();
49 }
50
51 @Override
52 public PreparedStatement prepareStatement(String sql) throws SQLException {
53 // TODO Auto-generated method stub
54 return conn.prepareStatement(sql);
55 }
56
57 @Override
58 public <T> T unwrap(Class<T> iface) throws SQLException {
59 // TODO Auto-generated method stub
60 return null;
61 }
62
63 @Override
64 public boolean isWrapperFor(Class<?> iface) throws SQLException {
65 // TODO Auto-generated method stub
66 return false;
67 }
68
69 @Override
70 public CallableStatement prepareCall(String sql) throws SQLException {
71 // TODO Auto-generated method stub
72 return null;
73 }
74
75 @Override
76 public String nativeSQL(String sql) throws SQLException {
77 // TODO Auto-generated method stub
78 return null;
79 }
80
81 @Override
82 public void setAutoCommit(boolean autoCommit) throws SQLException {
83 // TODO Auto-generated method stub
84
85 }
86
87 @Override
88 public boolean getAutoCommit() throws SQLException {
89 // TODO Auto-generated method stub
90 return false;
91 }
92
93 @Override
94 public void commit() throws SQLException {
95 // TODO Auto-generated method stub
96
97 }
98
99 @Override
100 public void rollback() throws SQLException {
101 // TODO Auto-generated method stub
102
103 }
104
105 @Override
106 public boolean isClosed() throws SQLException {
107 // TODO Auto-generated method stub
108 return false;
109 }
110
111 @Override
112 public DatabaseMetaData getMetaData() throws SQLException {
113 // TODO Auto-generated method stub
114 return null;
115 }
116
117 @Override
118 public void setReadOnly(boolean readOnly) throws SQLException {
119 // TODO Auto-generated method stub
120
121 }
122
123 @Override
124 public boolean isReadOnly() throws SQLException {
125 // TODO Auto-generated method stub
126 return false;
127 }
128
129 @Override
130 public void setCatalog(String catalog) throws SQLException {
131 // TODO Auto-generated method stub
132
133 }
134
135 @Override
136 public String getCatalog() throws SQLException {
137 // TODO Auto-generated method stub
138 return null;
139 }
140
141 @Override
142 public void setTransactionIsolation(int level) throws SQLException {
143 // TODO Auto-generated method stub
144
145 }
146
147 @Override
148 public int getTransactionIsolation() throws SQLException {
149 // TODO Auto-generated method stub
150 return 0;
151 }
152
153 @Override
154 public SQLWarning getWarnings() throws SQLException {
155 // TODO Auto-generated method stub
156 return null;
157 }
158
159 @Override
160 public void clearWarnings() throws SQLException {
161 // TODO Auto-generated method stub
162
163 }
164
165 @Override
166 public Statement createStatement(int resultSetType, int resultSetConcurrency) throws SQLException {
167 // TODO Auto-generated method stub
168 return null;
169 }
170
171 @Override
172 public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency)
173 throws SQLException {
174 // TODO Auto-generated method stub
175 return null;
176 }
177
178 @Override
179 public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency) throws SQLException {
180 // TODO Auto-generated method stub
181 return null;
182 }
183
184 @Override
185 public Map<String, Class<?>> getTypeMap() throws SQLException {
186 // TODO Auto-generated method stub
187 return null;
188 }
189
190 @Override
191 public void setTypeMap(Map<String, Class<?>> map) throws SQLException {
192 // TODO Auto-generated method stub
193
194 }
195
196 @Override
197 public void setHoldability(int holdability) throws SQLException {
198 // TODO Auto-generated method stub
199
200 }
201
202 @Override
203 public int getHoldability() throws SQLException {
204 // TODO Auto-generated method stub
205 return 0;
206 }
207
208 @Override
209 public Savepoint setSavepoint() throws SQLException {
210 // TODO Auto-generated method stub
211 return null;
212 }
213
214 @Override
215 public Savepoint setSavepoint(String name) throws SQLException {
216 // TODO Auto-generated method stub
217 return null;
218 }
219
220 @Override
221 public void rollback(Savepoint savepoint) throws SQLException {
222 // TODO Auto-generated method stub
223
224 }
225
226 @Override
227 public void releaseSavepoint(Savepoint savepoint) throws SQLException {
228 // TODO Auto-generated method stub
229
230 }
231
232 @Override
233 public Statement createStatement(int resultSetType, int resultSetConcurrency, int resultSetHoldability)
234 throws SQLException {
235 // TODO Auto-generated method stub
236 return null;
237 }
238
239 @Override
240 public PreparedStatement prepareStatement(String sql, int resultSetType, int resultSetConcurrency,
241 int resultSetHoldability) throws SQLException {
242 // TODO Auto-generated method stub
243 return null;
244 }
245
246 @Override
247 public CallableStatement prepareCall(String sql, int resultSetType, int resultSetConcurrency,
248 int resultSetHoldability) throws SQLException {
249 // TODO Auto-generated method stub
250 return null;
251 }
252
253 @Override
254 public PreparedStatement prepareStatement(String sql, int autoGeneratedKeys) throws SQLException {
255 // TODO Auto-generated method stub
256 return null;
257 }
258
259 @Override
260 public PreparedStatement prepareStatement(String sql, int[] columnIndexes) throws SQLException {
261 // TODO Auto-generated method stub
262 return null;
263 }
264
265 @Override
266 public PreparedStatement prepareStatement(String sql, String[] columnNames) throws SQLException {
267 // TODO Auto-generated method stub
268 return null;
269 }
270
271 @Override
272 public Clob createClob() throws SQLException {
273 // TODO Auto-generated method stub
274 return null;
275 }
276
277 @Override
278 public Blob createBlob() throws SQLException {
279 // TODO Auto-generated method stub
280 return null;
281 }
282
283 @Override
284 public NClob createNClob() throws SQLException {
285 // TODO Auto-generated method stub
286 return null;
287 }
288
289 @Override
290 public SQLXML createSQLXML() throws SQLException {
291 // TODO Auto-generated method stub
292 return null;
293 }
294
295 @Override
296 public boolean isValid(int timeout) throws SQLException {
297 // TODO Auto-generated method stub
298 return false;
299 }
300
301 @Override
302 public void setClientInfo(String name, String value) throws SQLClientInfoException {
303 // TODO Auto-generated method stub
304
305 }
306
307 @Override
308 public void setClientInfo(Properties properties) throws SQLClientInfoException {
309 // TODO Auto-generated method stub
310
311 }
312
313 @Override
314 public String getClientInfo(String name) throws SQLException {
315 // TODO Auto-generated method stub
316 return null;
317 }
318
319 @Override
320 public Properties getClientInfo() throws SQLException {
321 // TODO Auto-generated method stub
322 return null;
323 }
324
325 @Override
326 public Array createArrayOf(String typeName, Object[] elements) throws SQLException {
327 // TODO Auto-generated method stub
328 return null;
329 }
330
331 @Override
332 public Struct createStruct(String typeName, Object[] attributes) throws SQLException {
333 // TODO Auto-generated method stub
334 return null;
335 }
336
337 @Override
338 public void setSchema(String schema) throws SQLException {
339 // TODO Auto-generated method stub
340
341 }
342
343 @Override
344 public String getSchema() throws SQLException {
345 // TODO Auto-generated method stub
346 return null;
347 }
348
349 @Override
350 public void abort(Executor executor) throws SQLException {
351 // TODO Auto-generated method stub
352
353 }
354
355 @Override
356 public void setNetworkTimeout(Executor executor, int milliseconds) throws SQLException {
357 // TODO Auto-generated method stub
358
359 }
360
361 @Override
362 public int getNetworkTimeout() throws SQLException {
363 // TODO Auto-generated method stub
364 return 0;
365 }
366
367 }
测试类
1 package cn.jdbc_myConn;
2
3 import java.sql.Connection;
4 import java.sql.SQLException;
5
6 public class Test {
7 public static void main(String[] args) throws SQLException {
8
9 //获取连接
10 Connection conn= MyDataSource.getConnection();
11 System.out.println(conn);
12 conn.close();
13 }
14 }
时间： 2025-01-15 08:24:46