feat(postgres_java): added class JavaPostgreSqlVersion

postgres_java/README.md

@@ -1,5 +1,20 @@
 # Overview
 This project shows how Postgres and Java interact.
 
+# Notes
+The instruction
+
+```/etc/init.d/postgresql status```
+
+is equivalent with
+
+```systemctl status postgresql```
+
+.
+
+obx21
+
+firstairport21
+
 # Links
 [source](https://zetcode.com/java/postgresql/)

postgres_java/pom.xml

@@ -30,6 +30,18 @@
 
     <build>
         <plugins>
+            <!--Set up the following plugin in order to run command line applications from Maven.
+            Run the app with mvn -q exec:java command.
+            The q runs mvn in quite mode.-->
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.6.0</version>
+                <configuration>
+                    <mainClass>de.swingbe.postgres_java.JavaPostgreSqlVersion
+                    </mainClass>
+                </configuration>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
@@ -72,7 +84,8 @@
                                 <transformer
                                         implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                     <manifestEntries>
-                                        <Main-Class>de.swingbe.postgres_java.Main
+                                        <Main-Class>
+                                            de.swingbe.postgres_java.Main
                                         </Main-Class>
                                     </manifestEntries>
                                 </transformer>
@@ -83,4 +96,13 @@
             </plugin>
         </plugins>
     </build>
+
+    <dependencies>
+        <!--Add the following dependency to include PostgreSQL  Java driver.-->
+        <dependency>
+            <groupId>org.postgresql</groupId>
+            <artifactId>postgresql</artifactId>
+            <version>42.3.1</version>
+        </dependency>
+    </dependencies>
 </project>

postgres_java/src/main/java/de/swingbe/postgres_java/JavaPostgreSqlVersion.java

@@ -0,0 +1,29 @@
+package de.swingbe.postgres_java;
+
+import java.sql.*;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class JavaPostgreSqlVersion {
+
+    public static void main(String[] args) {
+
+        String url = "jdbc:postgresql://localhost:5432/testdb";
+        String user = "usr";
+        String password = "#password";
+
+        try (Connection con = DriverManager.getConnection(url, user, password);
+             Statement st = con.createStatement();
+             ResultSet rs = st.executeQuery("SELECT VERSION()")) {
+
+            if (rs.next()) {
+                System.out.println(rs.getString(1));
+            }
+
+        } catch (SQLException ex) {
+
+            Logger lgr = Logger.getLogger(JavaPostgreSqlVersion.class.getName());
+            lgr.log(Level.SEVERE, ex.getMessage(), ex);
+        }
+    }
+}