Database connection pool & jdbctemplate

Catalog

1、 Database connection pool

1.1、 brief introduction

1.2、 Use （quickstart）

1.2.1、C3P0 Database connection pool

1.2.2、Druid Database connection pool  

2、JDBCTemplate Use

---

1、 Database connection pool

1.1、 brief introduction

1、 Database connection pool ： In short , It's actually a container ( aggregate ), Container for storing database connection objects .

  When the system is initialized , The container is created , Some connection objects will be requested in the container , When the user comes to access the database , Get the connection object from the container , After the user visits , The connection object is returned to the container .

2. The benefits of using connection pools ：
    1. Saving resource , Lifting performance
    2. Efficient user access , Faster response

3. Realization ：
    1. Standard interface ：DataSource    be located javax.sql It's a bag
        1. Method ：
              Get the connection ：getConnection()
             Return connection ：Connection.close().

If the connection object Connection It's taken from the connection pool , So called Connection.close() Method , The connection will no longer be closed . But return the connection

4、 Common database connection pool ：
        1. C3P0： Database connection pool technology
        2. Druid： Database connection pool implementation technology , Provided by Alibaba

5、 Use of jar Package download address ：jar Package download

1.2、 Use （quickstart）

1.2.1、C3P0 Database connection pool

Use steps ：    

       1. Import jar package ( Two ) c3p0-0.9.5.2.jar mchange-commons-java-0.2.12.jar ,
             Don't forget to import database drivers jar package   jar Package download address
        2. Define configuration file ：
            name ： c3p0.properties perhaps c3p0-config.xml
            route ： Put the document directly in src Under the directory .

        3. Create core objects Database connection pool object ComboPooledDataSource
        4. Get the connection ： getConnection

1、 Import jar package

2、 To write c3p0.xml The configuration file

<c3p0-config>
  <!--  Use the default configuration to read connection pool objects  -->
  <default-config>
  	<!--   Connection parameters  -->
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://localhost:3306/day10</property>
    <property name="user">root</property>
    <property name="password">123456</property>
    
    <!--  Connection pool parameters  -->
    <property name="initialPoolSize">5</property>
    <property name="maxPoolSize">10</property>
    <property name="checkoutTimeout">3000</property>
  </default-config>

  <named-config name="otherc3p0"> 
    <!--   Connection parameters  -->
    <property name="driverClass">com.mysql.jdbc.Driver</property>
    <property name="jdbcUrl">jdbc:mysql://localhost:3306/study</property>
    <property name="user">root</property>
    <property name="password">123456</property>
    
    <!--  Connection pool parameters  -->
    <property name="initialPoolSize">5</property>
    <property name="maxPoolSize">8</property>
    <property name="checkoutTimeout">1000</property>
  </named-config>
</c3p0-config>

3、 code

public class C3p0Test {
    public static void main(String[] args) throws SQLException {
        // TODO 1、 obtain datasource
        ComboPooledDataSource dataSource = new ComboPooledDataSource();
        // TODO 2、 obtain connection
        Connection connection = dataSource.getConnection();
        // TODO 3、 Definition sql
        String sql = "select * from person";
        // TODO 4、 perform sql
        ResultSet resultSet = connection.createStatement().executeQuery(sql);
        // TODO 5、 Print query data 
        while (resultSet.next()){
            String name = resultSet.getString("name");
            String email = resultSet.getString("email");
            System.out.println(name + "=======" + email);
        }
        // TODO 6、 Release resources 
        resultSet.close();
        connection.close();


    }

}

---

1.2.2、Druid Database connection pool  

Druid： Database connection pool implementation technology , Provided by Alibaba
    1. step ：
        1. Import jar package druid-1.0.9.jar 
        2. Define configuration file ：
             yes properties Formal
             You can call it anything , It can be placed in any directory
        3. Load profile Properties
        4. Get database connection pool object ： From the factory  DruidDataSourceFactory
        5. Get the connection ：getConnection

1、 Import jar package

2、 To write druid Configuration file for

druid.properties

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/day10
username=root
password=123456
initialSize=5
maxActive=10
maxWait=3000

3、 code

public class DruidTest {
    public static void main(String[] args) throws Exception {
        // TODO 1、 Load profile 
        Properties properties = new Properties();
        InputStream is = DruidTest.class.getClassLoader().getResourceAsStream("druid.properties");
        properties.load(is);

        // TODO 2、 establish datasource
        DataSource dataSource = DruidDataSourceFactory.createDataSource(properties);

        // TODO 3、 Get database connection object 
        Connection connection = dataSource.getConnection();

        // TODO 4、 Print objects directly   See if you can get the database connection object 
        System.out.println(connection);

    }
}

---

2、JDBCTemplate Use

  Use JDBCTemplate It can greatly reduce our writing jdbc Code for To simplify our development

jdbctemplate A quick start to

1、 Import jar package   

2、 code

public class JDBCTemplate_quickstart {
    public static void main(String[] args) throws Exception {
        // TODO 1、 Load profile 
        Properties properties = new Properties();
        InputStream is = DruidTest.class.getClassLoader().getResourceAsStream("druid.properties");
        properties.load(is);

        // TODO 2、 establish datasource
        DataSource dataSource = DruidDataSourceFactory.createDataSource(properties);

        // TODO 3、 establish JDBCTemplate object   Need to pass on a datasource
        JdbcTemplate template = new JdbcTemplate(dataSource);

        // TODO 4、 Definition sql
        String sql = "update person set addr = ' panama ' where id = ?";
        int count = template.update(sql,5); //  take id by 5 Change your address to Panama 
        System.out.println(count); //  Number of rows affected  1

        // TODO  Use jdbcTemplate It can greatly simplify the amount of our code   Only care about sql
    }
}

3、 test

  But the above code is still a lot , Then the tool classes we extracted before are used

1、 Create a new one util package , Put the extracted tool classes into the toolkit

//  This is a jdbc Tool class of 
public class JdbcUtil {
    //  Define a member variable datasource
    private static DataSource dataSource;

    static {
        try {
            // 1、 establish properties Collection classes 
            Properties properties = new Properties();
            // 2、 Load profile 
            InputStream resourceAsStream = JdbcUtil.class.getClassLoader().getResourceAsStream("druid.properties");
            properties.load(resourceAsStream);
           // 3、 Use database connection pool  druid
            dataSource = DruidDataSourceFactory.createDataSource(properties);

        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     *  return datasource Methods 
     * @return
     */
    public static DataSource getDataSource(){
        return dataSource;
    }
    
    /**
     *  Get database connection object 
     * @return  Data connection objects 
     */
    public static Connection getConnection() throws SQLException {
        return dataSource.getConnection();
    }
    /**
     *  Release resources 
     *
     * @param stmt
     * @param conn
     */
    public static void close(Statement stmt, Connection conn) {
        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    public static void close(PreparedStatement pstmt, Connection conn) {
        if (pstmt != null) {
            try {
                pstmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }


    /**
     *  Release resources 
     *
     * @param stmt
     * @param conn
     */
    public static void close(ResultSet rs, Statement stmt, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    public static void close(ResultSet rs, PreparedStatement stmt, Connection conn) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (conn != null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}

2、 Use JDBCTemplate

public class JDBCTemplate_quickstart2 {
    public static void main(String[] args) throws Exception {

        // 1、 Create a template object 
        JdbcTemplate template = new JdbcTemplate(JdbcUtil.getDataSource());
        // 2、 Definition sql
        String sql = "select count(*) from person";
        // 3、 Use template perform sql
        Integer count = template.queryForObject(sql, Integer.class);
        System.out.println(count);

    }
}

This makes it look more concise And we just need to focus on sql Sentence can be used