feat(postgres_java): added class JavaPostgreSqlProperties.java

postgres_java/pom.xml

@@ -38,7 +38,7 @@
                 <artifactId>exec-maven-plugin</artifactId>
                 <version>1.6.0</version>
                 <configuration>
-                    <mainClass>de.swingbe.postgres_java.JavaPostgreSqlRetrieve
+                    <mainClass>de.swingbe.postgres_java.JavaPostgreSqlProperties
                     </mainClass>
                 </configuration>
             </plugin>
@@ -85,7 +85,7 @@
                                         implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                                     <manifestEntries>
                                         <Main-Class>
-                                            de.swingbe.postgres_java.JavaPostgreSqlRetrieve
+                                            de.swingbe.postgres_java.JavaPostgreSqlProperties
                                         </Main-Class>
                                     </manifestEntries>
                                 </transformer>

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

@@ -0,0 +1,61 @@
+package de.swingbe.postgres_java;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.sql.*;
+import java.util.Properties;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class JavaPostgreSqlProperties {
+
+    public static Properties readProperties() {
+
+        Properties props = new Properties();
+        Path path = Paths.get("src/main/resources/database.properties");
+
+        try {
+            BufferedReader br = Files.newBufferedReader(path, StandardCharsets.UTF_8);
+            props.load(br);
+        } catch (IOException e) {
+            Logger.getLogger(JavaPostgreSqlProperties.class.getName()).log(
+                    Level.SEVERE, null, e);
+        }
+        return props;
+    }
+
+    public static void main(String[] args) {
+
+        Properties props = readProperties();
+
+        String url = props.getProperty("db.url");
+        String user = props.getProperty("db.user");
+        String password = props.getProperty("db.password");
+
+        //get all columns from a table
+        String query = "SELECT * FROM authors";
+
+        //create prepared statement using placeholders instead of directly writing values
+        try (Connection con = DriverManager.getConnection(url, user, password);
+             PreparedStatement pst = con.prepareStatement(query);
+             ResultSet rs = pst.executeQuery()) {
+
+            //advance cursor to the next record
+            //return false if there are no more records in the result set
+            while (rs.next()) {
+                System.out.print(rs.getInt(1));
+                System.out.print(" | ");
+                System.out.println(rs.getString(2));
+            }
+
+        } catch (SQLException ex) {
+
+            Logger lgr = Logger.getLogger(JavaPostgreSqlProperties.class.getName());
+            lgr.log(Level.SEVERE, ex.getMessage(), ex);
+        }
+    }
+}

postgres_java/src/main/resources/database.properties

@@ -0,0 +1,3 @@
+db.url=jdbc:postgresql://localhost:5432/testdb
+db.user=usr
+db.passwd=password