package org.kodejava.util.zip;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipOutputStream;
public class ZippingFileExample {
public static void main(String[] args) {
String source = "data.txt";
String target = "data.zip";
try (ZipOutputStream zos =
new ZipOutputStream(new FileOutputStream(target));
InputStream is =
ZippingFileExample.class.getResourceAsStream("/" + source)) {
if (is != null) {
// Put a new ZipEntry in the ZipOutputStream
zos.putNextEntry(new ZipEntry(source));
int size;
byte[] buffer = new byte[1024];
// Read data to the end of the source file and write it
// to the zip output stream.
while ((size = is.read(buffer, 0, buffer.length)) > 0) {
zos.write(buffer, 0, size);
}
zos.closeEntry();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Category Archives: Java
How do I get all table names from a database?
package org.kodejava.jdbc;
import java.sql.*;
public class GettingTableListExample {
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)) {
// Gets the metadata of the database
DatabaseMetaData metaData = connection.getMetaData();
String[] types = {"TABLE"};
ResultSet rs = metaData.getTables("kodejava", "kodejava", "%", types);
while (rs.next()) {
String tableCatalog = rs.getString(1);
String tableSchema = rs.getString(2);
String tableName = rs.getString(3);
System.out.printf("%s - %s - %s%n",
tableCatalog, tableSchema, tableName);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
Here is the result:
kodejava - null - author
kodejava - null - book_author
kodejava - null - book
Maven Dependencies
<dependency>
<groupId>com.mysql</groupId>
<artifactId>mysql-connector-j</artifactId>
<version>8.4.0</version>
</dependency>
How do I drop table from a database?
This example is to show you how to delete or drop a table from your database. Basically we just send a DROP TABLE command and specify the table name to be deleted to the database. The example below show you how to do it in MySQL database.
package org.kodejava.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
public class DropTableExample {
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)) {
// To delete a table from database we use the DROP TABLE
// command and specify the table name to be dropped
String sql = "DROP TABLE IF EXISTS book";
// Create a statement
Statement statement = connection.createStatement();
// Execute the statement to delete the table
statement.execute(sql);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
Maven Dependencies
<dependency>
<groupId>com.mysql</groupId>
<artifactId>mysql-connector-j</artifactId>
<version>8.4.0</version>
</dependency>
How do I create a table in a database?
In this example you can see how to create a table in MySQL database. We create a table called book with the following fields, id, isbn, title, published_year and price. We start by creating a connection to the database and execute the create table query.
package org.kodejava.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
public class CreateTableExample {
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)) {
String sql = """
CREATE TABLE book
(
id bigint(20) unsigned NOT NULL AUTO_INCREMENT,
isbn varchar(50) NOT NULL,
title varchar(100) NOT NULL,
published_year int(11) DEFAULT NULL,
price decimal(10, 2) NOT NULL DEFAULT '0.00',
PRIMARY KEY (id)
)
""";
Statement statement = connection.createStatement();
statement.execute(sql);
} catch (SQLException e) {
e.printStackTrace();
}
}
}
Maven Dependencies
<dependency>
<groupId>com.mysql</groupId>
<artifactId>mysql-connector-j</artifactId>
<version>8.4.0</version>
</dependency>
How do I know the number of rows affected when updating data in database table?
In this example you can see how to get number of rows or records affected when we update records in the database. The executeUpdate() method of Statement or PreparedStatement return an integer value which tell us how many records was affected by the executed command.
Note that when the return value for executeUpdate() method is 0, it can mean one of two things: (1) the statement executed was an update statement that affected zero row, or (2) the statement executed was a DDL statement such as statement to create a table in a database.
package org.kodejava.jdbc;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
public class HowManyRowExample {
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)) {
String sql = "UPDATE book SET title = ?, published_year = ? WHERE id = ?";
PreparedStatement ps = connection.prepareStatement(sql);
ps.setString(1, "Java 8 in Action, First Edition");
ps.setInt(2, 2014);
ps.setLong(3, 1L);
int rows = ps.executeUpdate();
System.out.printf("%d row(s) updated!", rows);
} catch (Exception e) {
e.printStackTrace();
}
}
}
The result of the code snippet above:
1 row(s) updated!
Maven Dependencies
<dependency>
<groupId>com.mysql</groupId>
<artifactId>mysql-connector-j</artifactId>
<version>8.4.0</version>
</dependency>