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BAEL-1818 - A Guide to Connection Pools in Java (#4735) 

* Strange git issue with README.MD, wouldn't revert the file

* Initial Commit

* Initial Commit

* Update pom.xml

* Update pom.xml

* Initial Commit

* Update pom.xml

* Update source files

* Update source files

* Update source files

* Update source files

* Update Application.java

* Update pom.xml

* Update HikariCPDataSourceUnitTest class

* Update HikariCPDataSourceUnitTest.java

* Update pom.xml

* Update unit test classes

* Update BasicConnectionPoolUnitTest.java

* Fix indentation in DBCDDataSource class

* Update DBCPDataSource.java

* Update BasicConnectionPool class

* Update BasicConnectionPool class

* Update BasicConnectionPool.java

* Update BasicConnectionPool.java

* Update pom.xml

* Update pom.xml

* BAEL-1818 Refactored getConnection(), added shutdown(), cleaned up pom.xml

* BAEL-1818 Removed getConnectionPool(), upgraded c3po version

* BAEL-1818 Deleted obsolete connectionpool module

* BAEL-1818 Deleted obsolete connectionpool module
This commit is contained in:
Alejandro Gervasio 2018-07-20 20:28:01 -03:00 committed by Predrag Maric
parent 86daa854d2
commit ac801b4319
10 changed files with 328 additions and 5 deletions
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36
core-java/pom.xml
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@ -1,5 +1,5 @@
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.baeldung</groupId>
<artifactId>core-java</artifactId>
@ -73,9 +73,10 @@
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<version>${assertj-core.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>commons-codec</groupId>
<artifactId>commons-codec</artifactId>
@ -146,6 +147,21 @@
<artifactId>icu4j</artifactId>
<version>${icu4j.version}</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-dbcp2</artifactId>
<version>${commons-dbcp2.version}</version>
</dependency>
<dependency>
<groupId>com.zaxxer</groupId>
<artifactId>HikariCP</artifactId>
<version>${HikariCP.version}</version>
</dependency>
<dependency>
<groupId>com.mchange</groupId>
<artifactId>c3p0</artifactId>
<version>${c3p0.version}</version>
</dependency>
</dependencies>
<build>
@ -301,7 +317,7 @@
</arguments>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-javadoc-plugin</artifactId>
@ -348,6 +364,7 @@
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>${exec-maven-plugin.version}</version>
<executions>
<execution>
<id>run-benchmarks</id>
@ -375,6 +392,7 @@
</profiles>
<properties>
<!-- marshalling -->
<jackson.version>2.8.5</jackson.version>
<gson.version>2.8.2</gson.version>
@ -395,16 +413,23 @@
<vavr.version>0.9.0</vavr.version>
<!-- testing -->
<assertj.version>3.6.1</assertj.version>
<assertj-core.version>3.10.0</assertj-core.version>
<!-- JDBC pooling frameworks -->
<commons-dbcp2.version>2.4.0</commons-dbcp2.version>
<HikariCP.version>3.2.0</HikariCP.version>
<c3p0.version>0.9.5.2</c3p0.version>
<!-- maven plugins -->
<maven-surefire-plugin.version>2.19.1</maven-surefire-plugin.version>
<springframework.spring-web.version>4.3.4.RELEASE</springframework.spring-web.version>
<springframework.boot.spring-boot-starter.version>1.5.8.RELEASE</springframework.boot.spring-boot-starter.version>
<javamoney.moneta.version>1.1</javamoney.moneta.version>
<h2database.version>1.4.197</h2database.version>
<esapi.version>2.1.0.1</esapi.version>
<jmh-core.version>1.19</jmh-core.version>
<jmh-generator-annprocess.version>1.19</jmh-generator-annprocess.version>
<maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
<javax.mail.version>1.5.0-b01</javax.mail.version>
@ -412,7 +437,8 @@
<onejar-maven-plugin.version>1.4.4</onejar-maven-plugin.version>
<maven-shade-plugin.version>3.1.1</maven-shade-plugin.version>
<spring-boot-maven-plugin.version>2.0.3.RELEASE</spring-boot-maven-plugin.version>
<exec-maven-plugin.version>1.6.0</exec-maven-plugin.version>
<icu4j.version>61.1</icu4j.version>
</properties>
</project>
</project>

87
core-java/src/main/java/com/baeldung/connectionpool/connectionpools/BasicConnectionPool.java Normal file
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@ -0,0 +1,87 @@
package com.baeldung.connectionpool.connectionpools;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class BasicConnectionPool implements ConnectionPool {
private final String url;
private final String user;
private final String password;
private final List<Connection> connectionPool;
private final List<Connection> usedConnections = new ArrayList<>();
private static final int INITIAL_POOL_SIZE = 10;
private final int MAX_POOL_SIZE = 20;
public static BasicConnectionPool create(String url, String user, String password) throws SQLException {
List<Connection> pool = new ArrayList<>(INITIAL_POOL_SIZE);
for (int i = 0; i < INITIAL_POOL_SIZE; i++) {
pool.add(createConnection(url, user, password));
}
return new BasicConnectionPool(url, user, password, pool);
}
private BasicConnectionPool(String url, String user, String password, List<Connection> connectionPool) {
this.url = url;
this.user = user;
this.password = password;
this.connectionPool = connectionPool;
}
@Override
public Connection getConnection() throws SQLException {
if (connectionPool.size() == 0) {
if (usedConnections.size() < MAX_POOL_SIZE) {
connectionPool.add(createConnection(url, user, password));
} else {
throw new RuntimeException("Maximum pool size reached, no available connections!");
}
}
Connection connection = connectionPool.remove(connectionPool.size() - 1);
usedConnections.add(connection);
return connection;
}
@Override
public boolean releaseConnection(Connection connection) {
connectionPool.add(connection);
return usedConnections.remove(connection);
}
private static Connection createConnection(String url, String user, String password) throws SQLException {
return DriverManager.getConnection(url, user, password);
}
public int getSize() {
return connectionPool.size() + usedConnections.size();
}
@Override
public String getUrl() {
return url;
}
@Override
public String getUser() {
return user;
}
@Override
public String getPassword() {
return password;
}
public void shutdown() throws SQLException {
for (Connection c : usedConnections) {
this.releaseConnection(c);
}
for (Connection c : connectionPool) {
c.close();
}
connectionPool.clear();
}
}

28
core-java/src/main/java/com/baeldung/connectionpool/connectionpools/C3poDataSource.java Normal file
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@ -0,0 +1,28 @@
package com.baeldung.connectionpool.connectionpools;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import java.beans.PropertyVetoException;
import java.sql.Connection;
import java.sql.SQLException;
public class C3poDataSource {
private static final ComboPooledDataSource cpds = new ComboPooledDataSource();
static {
try {
cpds.setDriverClass("org.h2.Driver");
cpds.setJdbcUrl("jdbc:h2:mem:test");
cpds.setUser("user");
cpds.setPassword("password");
} catch (PropertyVetoException e) {
e.printStackTrace();
}
}
public static Connection getConnection() throws SQLException {
return cpds.getConnection();
}
private C3poDataSource(){}
}

18
core-java/src/main/java/com/baeldung/connectionpool/connectionpools/ConnectionPool.java Normal file
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@ -0,0 +1,18 @@
package com.baeldung.connectionpool.connectionpools;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
public interface ConnectionPool {
Connection getConnection() throws SQLException;
boolean releaseConnection(Connection connection);
String getUrl();
String getUser();
String getPassword();
}

25
core-java/src/main/java/com/baeldung/connectionpool/connectionpools/DBCPDataSource.java Normal file
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@ -0,0 +1,25 @@
package com.baeldung.connectionpool.connectionpools;
import java.sql.Connection;
import java.sql.SQLException;
import org.apache.commons.dbcp2.BasicDataSource;
public class DBCPDataSource {
private static final BasicDataSource ds = new BasicDataSource();
static {
ds.setUrl("jdbc:h2:mem:test");
ds.setUsername("user");
ds.setPassword("password");
ds.setMinIdle(5);
ds.setMaxIdle(10);
ds.setMaxOpenPreparedStatements(100);
}
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
private DBCPDataSource(){}
}

28
core-java/src/main/java/com/baeldung/connectionpool/connectionpools/HikariCPDataSource.java Normal file
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@ -0,0 +1,28 @@
package com.baeldung.connectionpool.connectionpools;
import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;
import java.sql.Connection;
import java.sql.SQLException;
public class HikariCPDataSource {
private static final HikariConfig config = new HikariConfig();
private static final HikariDataSource ds;
static {
config.setJdbcUrl("jdbc:h2:mem:test");
config.setUsername("user");
config.setPassword("password");
config.addDataSourceProperty("cachePrepStmts", "true");
config.addDataSourceProperty("prepStmtCacheSize", "250");
config.addDataSourceProperty("prepStmtCacheSqlLimit", "2048");
ds = new HikariDataSource(config);
}
public static Connection getConnection() throws SQLException {
return ds.getConnection();
}
private HikariCPDataSource(){}
}

69
core-java/src/test/java/com/baeldung/connectionpool/BasicConnectionPoolUnitTest.java Normal file
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@ -0,0 +1,69 @@
package com.baeldung.connectionpool;
import com.baeldung.connectionpool.connectionpools.BasicConnectionPool;
import com.baeldung.connectionpool.connectionpools.ConnectionPool;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;
import static org.assertj.core.api.Assertions.assertThat;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;
import org.junit.BeforeClass;
import org.junit.Test;
public class BasicConnectionPoolUnitTest {
private static ConnectionPool connectionPool;
@BeforeClass
public static void setUpBasicConnectionPoolInstance() throws SQLException {
connectionPool = BasicConnectionPool.create("jdbc:h2:mem:test", "user", "password");
}
@Test
public void givenBasicConnectionPoolInstance_whenCalledgetConnection_thenCorrect() throws Exception {
assertTrue(connectionPool.getConnection().isValid(1));
}
@Test
public void givenBasicConnectionPoolInstance_whenCalledreleaseConnection_thenCorrect() throws Exception {
Connection connection = connectionPool.getConnection();
assertThat(connectionPool.releaseConnection(connection)).isTrue();
}
@Test
public void givenBasicConnectionPoolInstance_whenCalledgetUrl_thenCorrect() {
assertThat(connectionPool.getUrl()).isEqualTo("jdbc:h2:mem:test");
}
@Test
public void givenBasicConnectionPoolInstance_whenCalledgetUser_thenCorrect() {
assertThat(connectionPool.getUser()).isEqualTo("user");
}
@Test
public void givenBasicConnectionPoolInstance_whenCalledgetPassword_thenCorrect() {
assertThat(connectionPool.getPassword()).isEqualTo("password");
}
@Test(expected = RuntimeException.class)
public void givenBasicConnectionPoolInstance_whenAskedForMoreThanMax_thenError() throws Exception {
// this test needs to be independent so it doesn't share the same connection pool as other tests
ConnectionPool cp = BasicConnectionPool.create("jdbc:h2:mem:test", "user", "password");
final int MAX_POOL_SIZE = 20;
for (int i = 0; i < MAX_POOL_SIZE + 1; i++) {
cp.getConnection();
}
fail();
}
@Test
public void givenBasicConnectionPoolInstance_whenSutdown_thenEmpty() throws Exception {
ConnectionPool cp = BasicConnectionPool.create("jdbc:h2:mem:test", "user", "password");
assertThat(((BasicConnectionPool)cp).getSize()).isEqualTo(10);
((BasicConnectionPool) cp).shutdown();
assertThat(((BasicConnectionPool)cp).getSize()).isEqualTo(0);
}
}

14
core-java/src/test/java/com/baeldung/connectionpool/C3poDataSourceUnitTest.java Normal file
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@ -0,0 +1,14 @@
package com.baeldung.connectionpool;
import com.baeldung.connectionpool.connectionpools.C3poDataSource;
import java.sql.SQLException;
import static org.junit.Assert.assertTrue;
import org.junit.Test;
public class C3poDataSourceUnitTest {
@Test
public void givenC3poDataSourceClass_whenCalledgetConnection_thenCorrect() throws SQLException {
assertTrue(C3poDataSource.getConnection().isValid(1));
}
}

14
core-java/src/test/java/com/baeldung/connectionpool/DBCPDataSourceUnitTest.java Normal file
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@ -0,0 +1,14 @@
package com.baeldung.connectionpool;
import com.baeldung.connectionpool.connectionpools.DBCPDataSource;
import java.sql.SQLException;
import static org.junit.Assert.assertTrue;
import org.junit.Test;
public class DBCPDataSourceUnitTest {
@Test
public void givenDBCPDataSourceClass_whenCalledgetConnection_thenCorrect() throws SQLException {
assertTrue(DBCPDataSource.getConnection().isValid(1));
}
}

14
core-java/src/test/java/com/baeldung/connectionpool/HikariCPDataSourceUnitTest.java Normal file
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@ -0,0 +1,14 @@
package com.baeldung.connectionpool;
import com.baeldung.connectionpool.connectionpools.HikariCPDataSource;
import java.sql.SQLException;
import static org.junit.Assert.assertTrue;
import org.junit.Test;
public class HikariCPDataSourceUnitTest {
@Test
public void givenHikariDataSourceClass_whenCalledgetConnection_thenCorrect() throws SQLException {
assertTrue(HikariCPDataSource.getConnection().isValid(1));
}
}