From: Roland Haeder <roland@mxchange.org>
Date: Thu, 30 Jul 2015 13:32:41 +0000 (+0200)
Subject: First atttempt of prepared statement
X-Git-Url: https://git.mxchange.org/?a=commitdiff_plain;h=f9fc2ec9a73e932e678cf6532225cd228d7cfa95;p=addressbook-swing.git

First atttempt of prepared statement
Signed-off-by:Roland Häder <roland@mxchange.org>
---

diff --git a/Addressbook/src/org/mxchange/addressbook/database/backend/DatabaseBackend.java b/Addressbook/src/org/mxchange/addressbook/database/backend/DatabaseBackend.java
index 9a66e94..70cfd81 100644
--- a/Addressbook/src/org/mxchange/addressbook/database/backend/DatabaseBackend.java
+++ b/Addressbook/src/org/mxchange/addressbook/database/backend/DatabaseBackend.java
@@ -47,8 +47,9 @@ public interface DatabaseBackend extends FrameworkInterface {
 	 * Some "getter" for total table row count
 	 * 
 	 * @return Total row count
+	 * @throws java.sql.SQLException If an SQL error occurs
 	 */
-	public int getTotalCount ();
+	public int getTotalCount () throws SQLException;
 
 	/**
 	 * Checks whether at least one row is found with given boolean value.
@@ -56,8 +57,9 @@ public interface DatabaseBackend extends FrameworkInterface {
 	 * @param columnName Column to check for boolean value
 	 * @param bool Boolean value to check
 	 * @return Whether boolean value is found and returns at least one row
+	 * @throws java.sql.SQLException If an SQL error occurs
 	 */
-	public boolean isRowFound (final String columnName, final boolean bool);
+	public boolean isRowFound (final String columnName, final boolean bool) throws SQLException;
 
 	/**
 	 * Rewinds backend
diff --git a/Addressbook/src/org/mxchange/addressbook/database/backend/mysql/MySqlDatabaseBackend.java b/Addressbook/src/org/mxchange/addressbook/database/backend/mysql/MySqlDatabaseBackend.java
index 8845521..8b0ad9f 100644
--- a/Addressbook/src/org/mxchange/addressbook/database/backend/mysql/MySqlDatabaseBackend.java
+++ b/Addressbook/src/org/mxchange/addressbook/database/backend/mysql/MySqlDatabaseBackend.java
@@ -19,6 +19,8 @@ package org.mxchange.addressbook.database.backend.mysql;
 import java.io.IOException;
 import java.sql.Connection;
 import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.text.MessageFormat;
 import java.util.Iterator;
@@ -40,6 +42,11 @@ public class MySqlDatabaseBackend extends BaseDatabaseBackend implements Databas
 	 */
 	private static Connection connection;
 
+	/**
+	 * Prepared statement for full row count
+	 */
+	private PreparedStatement totalRowCount;
+
 	/**
 	 * Constructor with table name
 	 * 
@@ -84,6 +91,18 @@ public class MySqlDatabaseBackend extends BaseDatabaseBackend implements Databas
 				this.getProperty("database.mysql.password") //NOI18N
 		);
 
+		// Is the connection really up?
+		if (MySqlDatabaseBackend.connection.isClosed()) {
+			// Connection is closed again
+			throw new SQLException("Connection is closed."); //NOI18N
+		}
+
+		// Debug message
+		this.getLogger().debug("Connection is up, preparing some statements ..."); //NOI18N
+
+		// Here, the connection is established, so prepare some statements
+		this.totalRowCount = MySqlDatabaseBackend.connection.prepareStatement("SELECT COUNT(`id`) AS `cnt` FROM ? LIMIT 1"); //NOI18N
+
 		// Trace message
 		this.getLogger().trace("EXIT!"); //NOI18N
 	}
@@ -97,7 +116,7 @@ public class MySqlDatabaseBackend extends BaseDatabaseBackend implements Databas
 	@Override
 	public void doShutdown () {
 		// This should not happen:
-		assert(MySqlDatabaseBackend.connection == null) : "connection is null"; //NOI18N
+		assert(MySqlDatabaseBackend.connection instanceof Connection) : MessageFormat.format("connection is not valid: {0}", MySqlDatabaseBackend.connection); //NOI18N
 
 		try {
 			// Close down database connection
@@ -108,8 +127,30 @@ public class MySqlDatabaseBackend extends BaseDatabaseBackend implements Databas
 	}
 
 	@Override
-	public int getTotalCount () {
-		throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
+	public int getTotalCount () throws SQLException{
+		// Nothing counted by default
+		int count = 0;
+
+		// Set table name
+		this.totalRowCount.setString(1, this.getTableName());
+
+		// Prepared statements are cool ...
+		if (this.totalRowCount.execute()) {
+			// Did fully work, so get result set
+			ResultSet set = this.totalRowCount.getResultSet();
+
+			// First rewind it
+			assert(set.last()) : ": last() failed"; //NOI18N
+
+			// Get integer from 'cnt' alias (see statement)
+			count = set.getInt("cnt"); //NOI18N
+
+			// Go back to beginning
+			set.beforeFirst();
+		}
+
+		// Return result
+		return count;
 	}
 
 	/**
@@ -120,7 +161,7 @@ public class MySqlDatabaseBackend extends BaseDatabaseBackend implements Databas
 	 * @return Whether boolean value is found and returns at least one row
 	 */
 	@Override
-	public boolean isRowFound (final String columnName, final boolean bool) {
+	public boolean isRowFound (final String columnName, final boolean bool) throws SQLException {
 		// Is at least one entry found?
 		if (this.getTotalCount() == 0) {
 			// No entry found at all