ORIGIN

JDBC Database Connection Pool

2023-02-13

JDBC Java Database Connection Pool 4 mins751 words

This article is note about learning Connection Pool.

Connection Pool

Connection pooling means that connections are reused rather than created each time a connection is requested. To facilitate connection reuse, a memory cache of database connections, called a connection pool, is maintained by a connection pooling module as a layer on top of any standard JDBC driver product.

Some open source Connection Pool

DBCP: offered by Apache, faster than c3p0, but has some bugs
C3P0: offered by open source organization. relatively slow, but with good stability. Advised by hibernate.
Proxool: an open project under sourceforge, can monitor the status of connection pool, but not so stable compared to c3p0
BoneCP: fast speed
Druid: offered by Alibaba, combine the best of BDCP, C3P0, Proxool, but speed is not sure to faster than BoneCP

Implements of Connection Pools

C3P0

download the source on sourceforge add \lib\c3p0-x.x.x.x.jar to /lib folder
then build path for it.

Method 1

get c3p0 database connection pool

ComboPooledDataSource cpds = new ComboPooledDataSource();
cpds.setDriverClass("com.mysql.jdbc.Driver"); // loads the jdbc driver
cpds.setJdbcUrl("jdbc:mysql://localhost:3306/testdb");
cpds.setUser("dbuser");
cpds.setPassword("dbpassword");

by setting related parameters, helps to manage the connection pool

1	cpds.setInitialPoolSize(10);

return connection

1 2	Connection conn = cpds.getConnection(); return conn;

Method 2 - xml config

create a new c3p0-config.xml file in /src folder

write the xml flie

<?xml version="1.0" encoding="UTF-8"?>
<c3p0-config>

  <named-config name="intergalactoApp"> 
    <!-- four base information for getting a connection  -->
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl ">jdbc:mysql://localhost:3306/test</property>
    <property name="user">root</property>
    <property name="password">123abc</property>

    <!-- basic properties to manage connection pool -->
    <property name="acquireIncrement">5</property> 
    <property name="initialPoolSize">10</property>
    <property name="minPoolSize">10</property>
    <property name="maxPoolSize">100</property>
    <property name="maxStatements">50</property>
    <property name="maxStatementsPerConnection">2</property>

  </named-config>
</c3p0-config>

acquireIncrement: when the connection is not enough, the number of connection that c3p0 will apply for to database server.
initialPoolSize: number of connection when initialize
minPoolSize: minimum number of connection the pool will maintain
maxPoolSize: maximum number of connection the pool will maintain
maxStatements: maximum number of Statement the pool will maintain
maxStatementsPerConnection: maximum number of Statement each connection can use

call the xml file

1 2	ComboPooledDataSource cpds = new ComboPooledDataSource("intergalactoApp"); Connection conn = cpds.getConnection();

but actually, it’s the new ComboPooledDataSource("intergalactoApp") should be write out side function wrapper. To avoid creating a pool each time getting a connection.

private static ComboPooledDataSource cpds = new ComboPooledDataSource("intergalactoApp");
public Connection testGetConnection2() throws Exception {
    Connection conn = cpds.getConnection();
    return conn;
}

DBCP

Download the bin file here https://commons.apache.org/proper/commons-dbcp/download_dbcp.cgi

Add commons-dbcp2-x.x.x.jar to file path

Also need to download the commons-pool2 and do the same thing. https://commons.apache.org/proper/commons-pool/download_pool.cgi

Method 1

public Connection testGetConnection() throws Exception {
    // create DBCP connection pool
    BasicDataSource source = new BasicDataSource();

    // set basic information
    source.setDriverClassName("com.mysql.jdbc.Driver");
    source.setUrl("jdbc://mysql///test");
    source.setUsername("root");
    source.setPassword("1122");

    // settting about manage pool
    source.setInitialSize(10);
    source.setMaxTotal(10);

    Connection conn = source.getConnection();
    return conn;
}

Method 2 - config file

creating a properties file

username=root
password=123
url=jdbc:mysql://localhost:3306/test
driverClassName=com.mysql.jdbc.Driver

initialSize=10

load file

// method 1
InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream("dbcp.properties");
// method 2
FileInputStream is = new FileInputStream(new File("src/dbcp.properties"));

pros.load(is);

whole code:

private static DataSource source;
static {
    try {
        Properties pros = new Properties();
        // InputStream is = ClassLoader.getSystemClassLoader().getResourceAsStream("dbcp.properties");
        FileInputStream is = new FileInputStream(new File("src/dbcp.properties"));
        pros.load(is);
        source = BasicDataSourceFactory.createDataSource(pros);
    } catch (Exception e) {
        e.printStackTrace();
    }
}
public Connection testGetConnection2() throws Exception {
    // create DBCP connection pool 
    Connection conn = source.getConnection();
    return conn;
}