How do I register out parameter in CallableStatement?

By Wayan in JDBC 0 Comment

This example show you how to register out parameter for executing a stored procedure using the CallableStatement.registerOutParameter() method call. We must register the out parameters before the query execution. The registerOutParameter() method takes two parameters, the index of the parameter and the sql data type of the out parameter.

package org.kodejava.jdbc;

import java.sql.*;

public class RegisterOutParameter {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            // Creates a CallableStatement for executing the stored
            // procedure
            String query = "call Get_Product_Detail_By_Name(?, ?, ?)";
            CallableStatement cb = connection.prepareCall(query);

            // Sets the input parameter
            cb.setString(1, "Data Structures, Algorithms");

            // Registers the out parameters
            cb.registerOutParameter(2, Types.VARCHAR);
            cb.registerOutParameter(3, Types.DECIMAL);

            // Executes the query
            cb.executeQuery();

            // Gets the query result output
            System.out.println("Name  : " + cb.getString(1));
            System.out.println("Code  : " + cb.getString(2));
            System.out.println("Price : " + cb.getBigDecimal(3));
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Here is the MySQL stored procedure that we call in the code above.

DELIMITER ;;
DROP PROCEDURE IF EXISTS `Get_Product_Detail_By_Name`;;
CREATE PROCEDURE `Get_Product_Detail_By_Name`(
    INOUT product_name VARCHAR(100),
    OUT product_code VARCHAR(20),
    OUT product_price DECIMAL(10, 2))
BEGIN
    SELECT code INTO product_code FROM product WHERE name = product_name;

    SELECT price INTO product_price FROM product WHERE name = product_name;
END;;
DELIMITER ;

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central

How do I use the unary operators?

By Wayan in Basic, Core API 0 Comment

The unary operators requires only one operand to operate on, it can perform operations such as incrementing or decrementing value by one, negating a value or inverting a value of a boolean expression.

The unary operators use the following symbols:

Symbol Description
+ unary plus operator; indicates positive value
- unary minus operator; negates a value
++ unary increment operator; increments value by one
-- unary decrement operator; decrements value by one
! unary logical complement operator; inverts a boolean value 
package org.kodejava.basic;

public class UnaryOperatorsDemo {
    public static void main(String[] args) {
        int result = +10;  // result = 10
        System.out.println("result = " + result);
        result--;          // result = 9
        System.out.println("result = " + result);
        result++;          // result = 10
        System.out.println("result = " + result);
        result = -result;  // result = -10;
        System.out.println("result = " + result);

        // The increment and decrement operators can be applied
        // before (prefix) or after (postfix) the operand. Both
        // of them will increment or decrement value by one. The
        // different is that the prefix version evaluates to the
        // incremented or decremented value while the postfix
        // version evaluates to the original value;
        --result;
        System.out.println("result = " + result);
        ++result;
        System.out.println("result = " + result);

        boolean status = result == -10;  // status = true
        System.out.println("status = " + status);
        status = !status;                // status = false;
        System.out.println("status = " + status);
    }
}

How do I use the arithmetic operators?

By Wayan in Basic, Core API 0 Comment

The following example show you how to use Java arithmetic operators. The operators consist of the multiplicative operators (* for multiplication, / for division), % for remainder of division) and the additive operators (+ for addition,- for subtraction).

You’ll also see we are using a combination of a simple assignment operator with the arithmetic operators to create compound assignments.

package org.kodejava.basic;

public class ArithmeticOperatorsDemo {
    public static void main(String[] args) {
        int result = 5 + 4;  // result = 9
        System.out.println("result = " + result);

        result = result - 2; // result = 7
        System.out.println("result = " + result);

        result = result * 4; // result = 28
        System.out.println("result = " + result);

        result = result / 7; // result = 4
        System.out.println("result = " + result);

        result = result % 3; // result = 1
        System.out.println("result = " + result);

        // Combining the arithmetic operators with a simple assignment
        // operators give us a compound assignment. We can write the
        // operation above in the following form. But as you can see
        // the above snippets is easier to read.
        result = 5 + 4; // result = 9
        System.out.println("result = " + result);

        result -= 2;    // result = 7
        System.out.println("result = " + result);

        result *= 4;    // result = 28
        System.out.println("result = " + result);

        result /= 7;    // result = 4
        System.out.println("result = " + result);

        result %= 3;    // result = 1
        System.out.println("result = " + result);
    }
}

How do I set the query timeout limit?

By Wayan in JDBC 1 Comment

The Statement.setQueryTimeout() method set the limit in seconds for query execution time. The execution has no timeout limit when the value is set to zero.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.SQLException;
import java.sql.DriverManager;

public class QueryTimeout {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            Statement stmt = connection.createStatement();

            // Sets the number of seconds the driver will wait for
            // a statement object to execute to the given number of
            // seconds. If the limit is exceeded, an SQLException
            // is thrown.
            stmt.setQueryTimeout(60);

            // Execute sql query
            ResultSet rs = stmt.executeQuery("select * from product");

            while (rs.next()) {
                System.out.println("code: " + rs.getString("code") + 
                                   ", product: " + rs.getString("name") + 
                                   ", price: " + rs.getDouble("price"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central

How do I get peak live threads count?

By Wayan in Core API, Management 0 Comment 
package org.kodejava.lang.management;

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadMXBean;

public class PeakThreadCount {
    public static void main(String[] args) {
        // Get the managed bean for the thread system of the Java
        // virtual machine.
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();

        // Get the peak live thread count since the Java virtual
        // machine started or peak was reset.
        int peakThreadCount = bean.getPeakThreadCount();
        System.out.println("Peak Thread Count = " + peakThreadCount);
    }
}