How do I store BLOBs data into database?

By Wayan in JDBC 1 Comment

Database BLOBs (Binary Large Objects) can be used to store any data, such as images, audio, or video files, for instance. This example shows you how we use JDBC library to store image in our database. To send the binary information to the database, we can call the PreparedStatement.setBinaryStream() method and pass the appropriate input stream and its size.

package org.kodejava.jdbc;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class BlobDemo {
    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 conn =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            conn.setAutoCommit(false);

            String sql = "INSERT INTO product_image " +
                         "(product_id, name, description, image) VALUES (?, ?, ?, ?)";
            String image = "/uml-distilled-3rd-edition.jpg";

            try (PreparedStatement stmt = conn.prepareStatement(sql);
                 InputStream is = BlobDemo.class.getResourceAsStream(image)) {

                stmt.setLong(1, 1L);
                stmt.setString(2, "uml-distilled-3rd-edition.jpg");
                stmt.setString(3, "UML Distilled 3rd Edition");
                stmt.setBinaryStream(4, is);
                stmt.execute();

                conn.commit();
            } catch (Exception e) {
                conn.rollback();
                e.printStackTrace();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

The structure of product_image table.

CREATE TABLE `product_image`
(
    `id`          bigint(20) unsigned NOT NULL AUTO_INCREMENT,
    `product_id`  bigint(20) unsigned NOT NULL,
    `name`        varchar(255)        NOT NULL,
    `description` varchar(255) DEFAULT NULL,
    `image`       blob,
    PRIMARY KEY (`id`),
    KEY `product_id` (`product_id`),
    CONSTRAINT `product_image_ibfk_1` FOREIGN KEY (`product_id`) REFERENCES `product` (`id`)
) ENGINE = InnoDB;

Maven Dependencies

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

Maven Central

How do I execute stored procedure?

By Wayan in JDBC 0 Comment

Stored-procedure are user-generated functions or procedures that, once created in the database, it can be called by the client applications, such as Java application. In this example we’ll demonstrate how to use the JDBC java.sql.CallableStatement to call a stored procedure. The store procedure in this example is just for selecting records from the products table.

package org.kodejava.jdbc;

import java.sql.*;

public class CallableStatementDemo {
    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)) {

            // Create a CallableStatement to execute the GetAllProducts() 
            // procedure.
            CallableStatement stmt =
                    connection.prepareCall("{CALL Get_All_Products()}");

            ResultSet rs = stmt.executeQuery();
            while (rs.next()) {
                System.out.println(rs.getLong("id") + "\t"
                        + rs.getString("code") + "\t"
                        + rs.getString("name") + "\t"
                        + rs.getDouble("price"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Below is the stored procedure definition that was executed in the code above.

DELIMITER ;;
CREATE PROCEDURE `Get_All_Products`()
BEGIN
    SELECT * FROM product;
END;;
DELIMITER ;

When running the code snippet, the result will be something like this:

1   P0000001    UML Distilled 3rd Edition   25.0
3   P0000003    PHP Programming 20.0
4   P0000004    Longman Active Study Dictionary 40.0
5   P0000005    Ruby on Rails   24.0
6   P0000006    Championship Manager    0.0
7   P0000007    Transport Tycoon Deluxe 0.0
8   P0000008    Roller Coaster Tycoon 3 0.0
9   P0000009    Pro Evolution Soccer    0.0
10  P0000010    Data Structures, Algorithms 50.99

Maven Dependencies

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

Maven Central

How do I sort items in a Set?

By Wayan in Core API, Util Package 0 Comment

The trick to sort a java.util.Set is to use the implementation of a java.util.SortedSet such as the java.util.TreeSet class. The example below shows you the result of using the java.util.TreeSet class, in which the items in it will be sorted based on the element’s natural order.

package org.kodejava.util;

import java.util.Set;
import java.util.TreeSet;

public class TreeSetDemo {
    public static void main(String[] args) {
        // The TreeSet class is an implementation of a SortedSet, this means
        // that when you are using the TreeSet to store you data collections
        // you'll get the items ordered base on its elements natural order.
        Set<String> set = new TreeSet<>();

        // In the example below we add some letters to the TreeSet, this mean
        // that the alphabets will be ordered based on the alphabet order
        // which is from A to Z.
        set.add("Z");
        set.add("A");
        set.add("F");
        set.add("B");
        set.add("H");
        set.add("X");
        set.add("N");

        for (String item : set) {
            System.out.print(item + " ");
        }
    }
}

This demo prints:

A B F H N X Z

How do I create a string search and replace using regex?

By Wayan in Regex 0 Comment

In this example you’ll see how we can create a small search and replace program using the regular expression classes in Java. The code below will replace all the brown words to red.

package org.kodejava.regex;

import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class StringReplace {
    public static void main(String[] args) {
        String source = "The quick brown fox jumps over the brown lazy dog.";
        String find = "brown";
        String replace = "red";

        // Compiles the given regular expression into a pattern.
        Pattern pattern = Pattern.compile(find);

        // Creates a matcher that will match the given input against the
        // pattern.
        Matcher matcher = pattern.matcher(source);

        // Replaces every subsequence of the input sequence that matches
        // the pattern with the given replacement string.
        String output = matcher.replaceAll(replace);

        System.out.println("Source = " + source);
        System.out.println("Output = " + output);
    }
}

The result of the code snippet is:

Source = The quick brown fox jumps over the brown lazy dog.
Output = The quick red fox jumps over the red lazy dog.

How do I do regular expression in Java?

By Wayan in Regex 0 Comment

This example demonstrates how we do regular expression in Java. The regular expression classes is in the java.uti.regex package. The main class including the java.util.regex.Pattern class and the java.util.regex.Matcher class.

In this example we are only testing to match a string literal if it is exists in the following sentence, we are searching the word “lazy”.

package org.kodejava.regex;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexDemo {
    public static void main(String[] args) {
        /*
         * To create a Pattern instance we must call the static method
         * called compile() in the Pattern class. Pattern object is
         * the compiled representation of a regular expression.
         */
        Pattern pattern = Pattern.compile("lazy");

        /*
         * The Matcher class also doesn't have the public constructor
         * so to create a matcher call the Pattern's class matcher()
         * method. The Matcher object itself is the engine that match
         * the input string against the provided pattern.
         */
        String input = "The quick brown fox jumps over the lazy dog";
        Matcher matcher = pattern.matcher(input);

        while (matcher.find()) {
            System.out.format("Text \"%s\" found at %d to %d.%n",
                    matcher.group(), matcher.start(), matcher.end());
        }
    }
}

The output of the code snippet above is:

Text "lazy" found at 35 to 39.