From f1f53140fa1f2bc46c4576f953a8634dd8a5cb22 Mon Sep 17 00:00:00 2001
From: goik <goik@hdm-stuttgart.de>
Date: Sat, 20 Oct 2012 13:04:23 +0200
Subject: [PATCH] Database connection parameters as Java properties. Javadoc
PersistenceHandler class completetd
---
.../Jdbc/src/sda/jdbc/intro/v1/DbProps.java | 22 ++++
.../sda/jdbc/intro/v1/PersistenceHandler.java | 104 ++++++++++++------
.../intro/v1/UsagePersistenceHandler.java | 18 +++
.../src/sda/jdbc/intro/v1/database.properties | 3 +
4 files changed, 114 insertions(+), 33 deletions(-)
create mode 100644 ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/DbProps.java
create mode 100644 ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/UsagePersistenceHandler.java
create mode 100644 ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/database.properties
diff --git a/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/DbProps.java b/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/DbProps.java
new file mode 100644
index 000000000..0bea232e0
--- /dev/null
+++ b/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/DbProps.java
@@ -0,0 +1,22 @@
+package sda.jdbc.intro.v1;
+
+import java.util.MissingResourceException;
+import java.util.ResourceBundle;
+
+public class DbProps {
+ private static final String BUNDLE_NAME = "sda.jdbc.intro.v1.database";
+
+ private static final ResourceBundle RESOURCE_BUNDLE = ResourceBundle
+ .getBundle(BUNDLE_NAME);
+
+ private DbProps() {
+ }
+
+ public static String getString(String key) {
+ try {
+ return RESOURCE_BUNDLE.getString(key);
+ } catch (MissingResourceException e) {
+ return '!' + key + '!';
+ }
+ }
+}
diff --git a/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/PersistenceHandler.java b/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/PersistenceHandler.java
index 700dec67f..a07f4e2bf 100644
--- a/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/PersistenceHandler.java
+++ b/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/PersistenceHandler.java
@@ -5,13 +5,25 @@ import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
-
/**
- * @author goik
+ * Handle database communication. There are two
+ * distinct internal states <q>disconnected</q> and <q>connected</q>, see
+ * {@link #isConnected()}. These two states may be toggled by invoking
+ * {@link #connect()} and {@link #disconnect()} respectively.
*
- * This class is intended to handle all database communication. There are two
- * distinct internal states "disconnected" and "connected", see
- * {@link #isConnected()}
+ * The following snippet illustrates the intended usage:
+ * <pre> public static void main(String[] args) {
+ final PersistenceHandler ph = new PersistenceHandler();
+ if (ph.connect()) {
+ if (!ph.add("Jim", "jim@foo.com")) {
+ System.err.println("Insert Error:" + ph.getErrorMessage());
+ }
+ } else {
+ System.err.println("Connect error:" + ph.getErrorMessage());
+ }
+ }</pre>
+ *
+ * @author goik
*/
public class PersistenceHandler {
@@ -19,20 +31,31 @@ public class PersistenceHandler {
Statement stmt = null;
String errorMessage = null;
-
+
/**
- * <dt><b>Precondition:</b><dd>
- * must be in "connected" state, see {@link #isConnected()}}
- *
- * Inserting a (name,email) record into the database server
- * @param name
- * @param email
- * @return true if the current data record has been successfully
- * inserted into the database server.
+ * Instance in <q>disconnected</q> state. See {@link #isConnected()}
*/
+ public PersistenceHandler() {/* only present here to supply javadoc comment */}
+
+ /**
+ * Inserting a (name, email) record into the database server. In case of
+ * errors corresponding messages may subsequently be retrieved by calling
+ * {@link #getErrorMessage()}.
+ *
+ * <dt><b>Precondition:</b></dt> <dd>must be in
+ * <q>connected</q> state, see {@link #isConnected()}</dd>
+ *
+ * @param name
+ * A person's name
+ * @param email
+ * A person's email address
+ *
+ * @return true if the current data record has been successfully inserted
+ * into the database server. false in case of error(s).
+ */
public boolean add(final String name, final String email){
- final String sql = "INSERT INTO Person VALUES('" + name + "', '" +
- email + "')";
+ final String sql = "INSERT INTO Person VALUES('" + name + "', '" +
+ email + "')";
try {
stmt.executeUpdate(sql);
return true;
@@ -42,33 +65,43 @@ public class PersistenceHandler {
}
}
- /**
- * If a call to {@link #add(String, String)}, {@link #connect()},
- * or {@link #disconnect()} returns false, the corresponding error explanation
- * my be retrieved
- * @return the error explanation corresponding to the latest failed operation,
- * null otherwise
- */
+ /**
+ * Retrieving error messages in case a call to {@link #add(String, String)},
+ * {@link #connect()}, or {@link #disconnect()} yields an error.
+ *
+ * @return the error explanation corresponding to the latest failed
+ * operation, null if no error yet occurred.
+ */
public String getErrorMessage() {
return errorMessage;
}
/**
- * Open a connection to a database server
- * <dt><b>Precondition:</b><dd>
- * must be in disconnected state, see {@link #isConnected()}
+ * Open a connection to a database server.
+ *
+ * <dt><b>Precondition:</b><dd>
+ * <dd>must be in <q>disconnected</q> state, see {@link #isConnected()}</dd>
+ *
+ * <dt><b>Precondition:</b><dd>
+ * <dd>The following properties must be set:
+ * <pre>PersistenceHandler.jdbcUrl=jdbc:mysql://localhost:3306/hdm
+PersistenceHandler.password=XYZ
+PersistenceHandler.username=foo</pre>
+ * </dd>
*
* @return true if connecting was successful
*/
public boolean connect () {
try {
conn = DriverManager.getConnection(
- "jdbc:mysql://localhost:3306/hdm", "hdmuser", "XYZ");
+ DbProps.getString("PersistenceHandler.jdbcUrl"),
+ DbProps.getString("PersistenceHandler.username"),
+ DbProps.getString("PersistenceHandler.password"));
try {
stmt = conn.createStatement();
return true;
} catch (SQLException e) {
- errorMessage = "Connection opened but Statement creation failed:\"" + e.getMessage() + "\".";
+ errorMessage = "Connection opened but Statement creation failed:\"" + e.getMessage() + "\".";
try {
conn.close();
} catch (SQLException ee) {
@@ -82,12 +115,17 @@ public class PersistenceHandler {
}
return false;
}
+
/**
- * Open a connection to a database server
- * <dt><b>Precondition:</b><dd>
- * must be in "connected" state, see {@link #isConnected()}
+ * Close a connection to a database server and clean up JDBC related resources
+ *
+ * Error messages in case of failure may subsequently be retrieved by
+ * calling {@link #getErrorMessage()}.
+ *
+ * <dt><b>Precondition:</b></dt>
+ * <dd>must be in <q>connected</q> state, see {@link #isConnected()}</dd>
*
- * @return true if disconnecting was successful
+ * @return true if disconnecting was successful, false in case error(s) occur.
*/
public boolean disconnect() {
boolean resultStatus = true;
@@ -113,7 +151,7 @@ public class PersistenceHandler {
}
/**
- * An instance can either be in "connected" or "disconnected" state. The
+ * An instance can either be in <q>connected</q> or <q>disconnected</q> state. The
* state can be toggled by invoking {@link #connect()} or
* {@link #disconnect()} respectively.
*
diff --git a/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/UsagePersistenceHandler.java b/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/UsagePersistenceHandler.java
new file mode 100644
index 000000000..ebdf5c95a
--- /dev/null
+++ b/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/UsagePersistenceHandler.java
@@ -0,0 +1,18 @@
+package sda.jdbc.intro.v1;
+
+public class UsagePersistenceHandler {
+
+ /**
+ * @param args
+ */
+ public static void main(String[] args) {
+ final PersistenceHandler ph = new PersistenceHandler();
+ if (ph.connect()) {
+ if (!ph.add("Jim", "jim@foo.com")) {
+ System.err.println("Insert Error:" + ph.getErrorMessage());
+ }
+ } else {
+ System.err.println("Connect error:" + ph.getErrorMessage());
+ }
+ }
+}
diff --git a/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/database.properties b/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/database.properties
new file mode 100644
index 000000000..32c844bac
--- /dev/null
+++ b/ws/eclipse/Jdbc/src/sda/jdbc/intro/v1/database.properties
@@ -0,0 +1,3 @@
+PersistenceHandler.jdbcUrl=jdbc:mysql://localhost:3306/hdm
+PersistenceHandler.password=XYZ
+PersistenceHandler.username=hdmuser
--
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