6 files changed, 393 insertions, 0 deletions
diff --git a/src/uk/org/ury/database/DatabaseDriver.java b/src/uk/org/ury/database/DatabaseDriver.java
new file mode 100644
index 0000000..0f03267
--- /dev/null
+++ b/src/uk/org/ury/database/DatabaseDriver.java
@@ -0,0 +1,122 @@
+package uk.org.ury.database;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+
+import uk.org.ury.database.exceptions.ConnectionFailureException;
+import uk.org.ury.database.exceptions.MissingCredentialsException;
+
+
+/**
+ * A database connection manager that connects to the URY databases 
+ * using suitably privileged accounts, and handles the processing 
+ * of SQL queries.
+ *
+ * @author Matt Windsor
+ *
+ */
+
+public class DatabaseDriver
+{ 
+  /* The JDBC path used to connect to the URY database. */
+  private String DATABASE_PATH = "jdbc:postgresql://localhost/membership";
+  
+  /* The database connection. */
+  private Connection conn;
+  
+  
+  /**
+   * Construct a new DatabaseDriver with the given user class.
+   * 
+   * @param userclass  The user class to log in to the database with.
+   * 
+   * @throws           IllegalArgumentException if the user class is 
+   *                   not supported (this should not happen).
+   *                   
+   * @throws           MissingCredentialsException if the user class 
+   *                   login credentials could not be loaded.
+   *                   
+   * @throws           ConnectionFailureException if the database 
+   *                   backend failed to connect to the database 
+   *                   server.
+   */
+  
+  public
+  DatabaseDriver (UserClass userclass) throws MissingCredentialsException, ConnectionFailureException
+  { 
+    DatabaseLogin login = null;
+    
+    switch (userclass)
+    {
+    case READ_ONLY:
+      login = DatabaseLogin.getLoginFromFile ("read_only.txt");
+      break;
+    case READ_WRITE:
+      login = DatabaseLogin.getLoginFromFile ("read_write.txt");
+    default:
+      throw new IllegalArgumentException ("Unused user class.");
+    }
+
+
+    try
+      {
+        System.out.println ("Trying to acquire connection...");
+        
+        connect (login);
+        
+        System.out.println ("...connection succeeded.");
+      }
+    catch (SQLException e)
+      {
+        throw new ConnectionFailureException (e.getMessage ());
+      }
+
+  }
+  
+  
+  public void
+  connect (DatabaseLogin login) throws SQLException
+  {
+    if (login == null)
+      throw new IllegalArgumentException ("Supplied null login.");
+    
+    if (login.getUsername () == null)
+      throw new IllegalArgumentException ("Login has no associated username.");
+    
+    if (login.getPassword () == null)
+      throw new IllegalArgumentException ("Login has no associated password.");
+    
+    conn = DriverManager.getConnection (DATABASE_PATH,
+                                        login.getUsername (),
+                                        login.getPassword ());
+  }
+  
+  
+  /**
+   * Execute a SQL statement.
+   * 
+   * @param sql  The SQL statement to execute.
+   * 
+   * @return     the JDBC results set.
+   */
+  
+  public ResultSet
+  executeQuery (String sql)
+  {
+    try 
+      {
+        Statement st = conn.createStatement ();
+        st.setFetchSize (50);
+        
+        return st.executeQuery (sql);
+      }
+    catch (SQLException e)
+      {
+        e.printStackTrace ();
+        return null;
+      }
+  }
+}
diff --git a/src/uk/org/ury/database/DatabaseLogin.java b/src/uk/org/ury/database/DatabaseLogin.java
new file mode 100644
index 0000000..e2f22bf
--- /dev/null
+++ b/src/uk/org/ury/database/DatabaseLogin.java
@@ -0,0 +1,150 @@
+/**
+ * 
+ */
+package uk.org.ury.database;
+
+import java.io.BufferedReader;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+import java.net.URL;
+
+import uk.org.ury.database.exceptions.MissingCredentialsException;
+
+
+/**
+ * A login username/password pair.
+ * 
+ * @author  Matt Windsor
+ */
+
+public class DatabaseLogin
+{
+  private String username;
+  private String password;
+  
+  
+  /**
+   * Create a new DatabaseLogin.
+   * 
+   * This constructor is intentionally left private to prevent 
+   * coders from hard-coding passwords.  Please read database 
+   * credentials from a source external to the program code.
+   * 
+   * @param username  The database username.
+   * @param password  The database password.
+   * 
+   * @see             getLoginFromFile
+   */
+  
+  private
+  DatabaseLogin (String username, String password)
+  {
+    this.username = username;
+    this.password = password;
+  }
+  
+  
+  /**
+   * Retrieve login credentials from a plaintext file.
+   * 
+   * The credentials should be listed in the following format:
+   * 
+   * username <newline>
+   * password
+   * 
+   * @param file  The filename of the file
+   * 
+   * @return      a new DatabaseLogin containing the information 
+   *              retrieved from the file.
+   * 
+   * @throws      IllegalArgumentException if the filename is null.
+   * 
+   * @throws      MissingCredentialsException if the file does not exist 
+   *              or is of the wrong format.
+   */
+  
+  public static DatabaseLogin
+  getLoginFromFile (String file) throws MissingCredentialsException
+  {
+    // Find the credentials file.
+    
+    if (file == null)
+      throw new IllegalArgumentException ("Supplied null credentials filename.");
+
+    URL fileURL = DatabaseLogin.class.getResource ("credentials/" + file);
+    
+    if (fileURL == null)
+      throw new MissingCredentialsException ("Credentials file "
+                                             + file
+                                             + " not found.");
+    
+    
+    String username = null;
+    String password = null;
+    BufferedReader reader = null;
+
+    
+    try
+      {
+        reader = new BufferedReader (new FileReader (fileURL.getFile ()));
+      }
+    catch (FileNotFoundException e)
+      {
+        throw new MissingCredentialsException ("Credentials file "
+                                               + file 
+                                               + " not found.");
+      }
+    
+    try
+      {
+        username = reader.readLine ();
+        password = reader.readLine ();
+      }
+    catch (IOException e)
+      {
+        throw new MissingCredentialsException ("Credentials file "
+                                               + file
+                                               + "is invalid.");
+      }
+    finally
+      {
+        try
+          {
+            reader.close ();
+          }
+        catch (IOException e)
+          {
+            // TODO Auto-generated catch block
+            e.printStackTrace ();
+          }
+      }
+
+    
+    DatabaseLogin login = new DatabaseLogin (username, password);
+    
+    return login;
+  }
+
+
+  /**
+   * @return  the username.
+   */
+  
+  public String
+  getUsername ()
+  {
+    return username;
+  }
+
+
+  /**
+   * @return  the password.
+   */
+  
+  public String
+  getPassword ()
+  {
+    return password;
+  }
+}
diff --git a/src/uk/org/ury/database/UserClass.java b/src/uk/org/ury/database/UserClass.java
new file mode 100644
index 0000000..8f30952
--- /dev/null
+++ b/src/uk/org/ury/database/UserClass.java
@@ -0,0 +1,24 @@
+/**
+ * 
+ */
+package uk.org.ury.database;
+
+
+/**
+ * The various user classes of the database driver.
+ * 
+ * These refer to various users in the database proper, and thus 
+ * grant various levels of permission to the program.
+ * 
+ * Please use the least privileged user class that works.  For most 
+ * cases, READ_ONLY should work perfectly.
+ * 
+ * @author  Matt Windsor
+ *
+ */
+
+public enum UserClass
+  {
+    READ_ONLY,
+    READ_WRITE
+  }
diff --git a/src/uk/org/ury/database/credentials/.gitignore b/src/uk/org/ury/database/credentials/.gitignore
new file mode 100644
index 0000000..2211df6
--- /dev/null
+++ b/src/uk/org/ury/database/credentials/.gitignore
@@ -0,0 +1 @@
+*.txt
diff --git a/src/uk/org/ury/database/exceptions/ConnectionFailureException.java b/src/uk/org/ury/database/exceptions/ConnectionFailureException.java
new file mode 100644
index 0000000..030b24f
--- /dev/null
+++ b/src/uk/org/ury/database/exceptions/ConnectionFailureException.java
@@ -0,0 +1,44 @@
+/**
+ * 
+ */
+package uk.org.ury.database.exceptions;
+
+/**
+ * Exception thrown when the database backend fails to connect to
+ * the database server, in absence of a more specific exception.
+ * 
+ * @author Matt Windsor
+ */
+
+public class ConnectionFailureException extends Exception
+{
+ /**
+   * 
+   */
+  private static final long serialVersionUID = -7353531873142099828L;
+
+
+/**
+  * Construct a new ConnectionFailureException with a 
+  * default reason.
+  */
+ 
+ public
+ ConnectionFailureException ()
+ {
+   super ("Connection failure.");
+ }
+ 
+ 
+ /**
+  * Construct a new ConnectionFailureException.
+  * 
+  * @param reason  The explanation for the exception.
+  */
+ 
+ public
+ ConnectionFailureException (String reason)
+ {
+   super (reason);
+ }
+}
diff --git a/src/uk/org/ury/database/exceptions/MissingCredentialsException.java b/src/uk/org/ury/database/exceptions/MissingCredentialsException.java
new file mode 100644
index 0000000..2e45526
--- /dev/null
+++ b/src/uk/org/ury/database/exceptions/MissingCredentialsException.java
@@ -0,0 +1,52 @@
+/**
+ * 
+ */
+package uk.org.ury.database.exceptions;
+
+/**
+ * Exception thrown when the database credentials required to 
+ * log into the URY database under a user class are missing, 
+ * and thus the log-in cannot continue.
+ * 
+ * The best practice for handling a MissingCredentialsException 
+ * is to attempt to log into the database with a less privileged 
+ * user class or, if the credentials for read-only access are 
+ * missing, give up.
+ * 
+ * @author Matt Windsor
+ */
+
+public class MissingCredentialsException extends Exception
+{
+  
+  /**
+   *
+   */
+  
+  private static final long serialVersionUID = -397479334359858162L;
+
+
+  /**
+   * Construct a new MissingCredentialsException with a 
+   * default reason.
+   */
+  
+  public
+  MissingCredentialsException ()
+  {
+    super ("Missing credentials.");
+  }
+  
+  
+  /**
+   * Construct a new MissingCredentialsException.
+   * 
+   * @param reason  The explanation for the exception.
+   */
+  
+  public
+  MissingCredentialsException (String reason)
+  {
+    super (reason);
+  }
+}