Add Database.getTableMetaData method to enable getting basic info about a Table (by name) without actually loading it. fixes feature request #33

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/trunk@979 f203690c-595d-4dc9-a70b-905162fa7fd2

3 files changed, 138 insertions, 4 deletions

diff --git a/src/main/java/com/healthmarketscience/jackcess/Database.java b/src/main/java/com/healthmarketscience/jackcess/Database.java
index 48273ef..42eb216 100644
--- a/src/main/java/com/healthmarketscience/jackcess/Database.java
+++ b/src/main/java/com/healthmarketscience/jackcess/Database.java
@@ -201,13 +201,21 @@ public interface Database extends Iterable<Table>, Closeable, Flushable
   public TableIterableBuilder newIterable();
   
   /**
-   * @param name Table name (case-insensitive)
-   * @return The table, or null if it doesn't exist
+   * @param name User table name (case-insensitive)
+   * @return The Table, or null if it doesn't exist (or is a system table)
    * @usage _general_method_
    */
   public Table getTable(String name) throws IOException;
 
   /**
+   * @param name Table name (case-insensitive), may be any table type
+   *             (i.e. includes system or linked tables).
+   * @return The meta data for the table, or null if it doesn't exist
+   * @usage _intermediate_method_
+   */
+  public TableMetaData getTableMetaData(String name) throws IOException;
+
+  /**
    * Finds all the relationships in the database between the given tables.
    * @usage _intermediate_method_
    */
diff --git a/src/main/java/com/healthmarketscience/jackcess/TableMetaData.java b/src/main/java/com/healthmarketscience/jackcess/TableMetaData.java
new file mode 100644
index 0000000..250932b
--- /dev/null
+++ b/src/main/java/com/healthmarketscience/jackcess/TableMetaData.java
@@ -0,0 +1,62 @@
+/*
+Copyright (c) 2016 James Ahlborn
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package com.healthmarketscience.jackcess;
+
+import java.io.IOException;
+
+/**
+ * Basic metadata about a single database Table.  This is the top-level
+ * information stored in a (local) database which can be retrieved without
+ * attempting to load the Table itself.
+ *
+ * @author James Ahlborn
+ * @usage _intermediate_class_
+ */
+public interface TableMetaData 
+{
+  /**
+   * The name of the table (as it is stored in the database)
+   */
+  public String getName();
+
+  /**
+   * {@code true} if this is a linked table, {@code false} otherwise.
+   */
+  public boolean isLinked();
+  
+  /**
+   * {@code true} if this is a system table, {@code false} otherwise.
+   */
+  public boolean isSystem();
+
+  /**
+   * The name of this linked table in the linked database if this is a linked
+   * table, {@code null} otherwise.
+   */
+  public String getLinkedTableName();
+
+  /**
+   * The name of this the linked database if this is a linked table, {@code
+   * null} otherwise.
+   */
+  public String getLinkedDbName();
+
+  /**
+   * Opens this table from the given Database instance.
+   */
+  public Table open(Database db) throws IOException;
+}
diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/DatabaseImpl.java b/src/main/java/com/healthmarketscience/jackcess/impl/DatabaseImpl.java
index 490e75f..99500dd 100644
--- a/src/main/java/com/healthmarketscience/jackcess/impl/DatabaseImpl.java
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/DatabaseImpl.java
@@ -60,6 +60,7 @@ import com.healthmarketscience.jackcess.Relationship;
 import com.healthmarketscience.jackcess.Row;
 import com.healthmarketscience.jackcess.RuntimeIOException;
 import com.healthmarketscience.jackcess.Table;
+import com.healthmarketscience.jackcess.TableMetaData;
 import com.healthmarketscience.jackcess.impl.query.QueryImpl;
 import com.healthmarketscience.jackcess.query.Query;
 import com.healthmarketscience.jackcess.util.CaseInsensitiveColumnMatcher;
@@ -928,6 +929,10 @@ public class DatabaseImpl implements Database
     return getTable(name, false);
   }
 
+  public TableMetaData getTableMetaData(String name) throws IOException {
+    return getTableInfo(name, true);
+  }  
+
   /**
    * @param tableDefPageNumber the page number of a table definition
    * @return The table, or null if it doesn't exist
@@ -962,15 +967,29 @@ public class DatabaseImpl implements Database
   private TableImpl getTable(String name, boolean includeSystemTables) 
     throws IOException 
   {
+    TableInfo tableInfo = getTableInfo(name, includeSystemTables);
+    return ((tableInfo != null) ? 
+            getTable(tableInfo, includeSystemTables) : null);
+  }
+
+  private TableInfo getTableInfo(String name, boolean includeSystemTables) 
+    throws IOException 
+  {
     TableInfo tableInfo = lookupTable(name);
     
     if ((tableInfo == null) || (tableInfo.pageNumber == null)) {
       return null;
     }
-    if(!includeSystemTables && isSystemObject(tableInfo.flags)) {
+    if(!includeSystemTables && tableInfo.isSystem()) {
       return null;
     }
 
+    return tableInfo;
+  }
+
+  private TableImpl getTable(TableInfo tableInfo, boolean includeSystemTables) 
+    throws IOException 
+  {
     if(tableInfo.isLinked()) {
 
       if(_linkedDbs == null) {
@@ -1884,7 +1903,7 @@ public class DatabaseImpl implements Database
   /**
    * Utility class for storing table page number and actual name.
    */
-  private static class TableInfo
+  private static class TableInfo implements TableMetaData
   {
     public final Integer pageNumber;
     public final String tableName;
@@ -1896,9 +1915,44 @@ public class DatabaseImpl implements Database
       flags = newFlags;
     }
 
+    public String getName() {
+      return tableName;
+    }
+    
     public boolean isLinked() {
       return false;
     }
+
+    public boolean isSystem() {
+      return isSystemObject(flags);
+    } 
+
+    public String getLinkedTableName() {
+      return null;
+    }
+
+    public String getLinkedDbName() {
+      return null;
+    }
+
+    public Table open(Database db) throws IOException {
+      return ((DatabaseImpl)db).getTable(this, true);
+    }
+
+    @Override
+    public String toString() {
+      ToStringBuilder sb = CustomToStringStyle.valueBuilder("TableMetaData")
+        .append("name", getName());
+        if(isSystem()) {
+          sb.append("isSystem", isSystem());
+        }
+        if(isLinked()) {
+          sb.append("isLinked", isLinked())
+            .append("linkedTableName", getLinkedTableName())
+            .append("linkedDbName", getLinkedDbName());
+        }
+        return sb.toString();
+    }
   }
 
   /**
@@ -1921,6 +1975,16 @@ public class DatabaseImpl implements Database
     public boolean isLinked() {
       return true;
     }
+
+    @Override
+    public String getLinkedTableName() {
+      return linkedTableName;
+    }
+
+    @Override
+    public String getLinkedDbName() {
+      return linkedDbName;
+    }
   }
 
   /**