<?xml version='1.0' encoding='utf-8'?>
 <Context>
 <resource
      name="jdbc/library"
      auth="Container"
      description="DB Connection"
      username="root"
      password="root"
      driverClassName="com.mysql.jdbc.Driver"
      url="jdbc:mysql://localhost:3306/library"
      maxActive="10"
      maxIdle="3"
      maxWait="100"
      factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
      type="javax.sql.DataSource"></resource>
 </Context>

<resource-ref>
  <description>DB Connection</description>
  <res-ref-name>jdbc/library</res-ref-name>
  <res-type>javax.sql.DataSource</res-type>
  <res-auth>Container</res-auth>
</resource-ref>

public void check() {
    try {
        InitialContext initialContext = new InitialContext();
        DataSource dataSource =    (DataSource)initialContext.lookup("java:comp/env/jdbc/library");
        Connection connection = dataSource.getConnection();
        Statement statement = connection.createStatement();
        ResultSet resultSet = statement.executeQuery("SELECT * FROM book");
        System.out.println(resultSet.next());
    } catch (NamingException e) {
        e.printStackTrace();
    } catch (SQLException e) {
        e.printStackTrace();
    }
 }