feat(driver-mongodb): support metadata

driver/datacap-driver-mongodb/src/main/java/io/edurt/datacap/driver/MongoResultSet.java

@@ -32,9 +32,10 @@ public class MongoResultSet
         implements ResultSet
 {
     private final MongoCursor<Document> cursor;
+    private final List<String> columnNames;
     private Document current;
     private boolean isClosed = false;
-    private final List<String> columnNames;
+    private ResultSetMetaData metadata;
 
     // Constructor
     // 构造函数
@@ -43,13 +44,15 @@ public MongoResultSet(AggregateIterable<Document> result)
         this.cursor = result.iterator();
         this.columnNames = new ArrayList<>();
         this.current = null;
+        this.metadata = null;
 
         // 预处理第一个文档以获取列名
         // Preprocess the first document to get the column names
         if (cursor.hasNext()) {
             Document first = result.first();
             if (first != null) {
                 columnNames.addAll(first.keySet());
+                this.metadata = new MongoResultSetMetaData(columnNames, first);
             }
         }
     }
@@ -224,7 +227,9 @@ public String getCursorName()
     public ResultSetMetaData getMetaData()
             throws SQLException
     {
-        return null;
+        checkClosed();
+
+        return metadata;
     }
 
     @Override

driver/datacap-driver-mongodb/src/main/java/io/edurt/datacap/driver/MongoResultSetMetaData.java

@@ -0,0 +1,237 @@
+package io.edurt.datacap.driver;
+
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import org.bson.Document;
+
+import java.sql.ResultSetMetaData;
+import java.sql.SQLException;
+import java.sql.Types;
+import java.util.List;
+import java.util.Map;
+
+@SuppressFBWarnings(value = {"NP_NONNULL_RETURN_VIOLATION", "EI_EXPOSE_REP2"})
+public class MongoResultSetMetaData
+        implements ResultSetMetaData
+{
+    private final List<String> columnNames;
+    private final Map<String, Object> sampleRow;
+
+    // Constructor
+    // 构造函数
+    public MongoResultSetMetaData(List<String> columnNames, Document sampleRow)
+    {
+        this.columnNames = columnNames;
+        this.sampleRow = sampleRow;
+    }
+
+    // Get number of columns
+    // 获取列数
+    @Override
+    public int getColumnCount()
+            throws SQLException
+    {
+        return columnNames.size();
+    }
+
+    // Get column name
+    // 获取列名
+    @Override
+    public String getColumnName(int column)
+            throws SQLException
+    {
+        checkColumnIndex(column);
+        return columnNames.get(column - 1);
+    }
+
+    // Get column label
+    // 获取列标签
+    @Override
+    public String getColumnLabel(int column)
+            throws SQLException
+    {
+        return getColumnName(column);
+    }
+
+    // Get column type
+    // 获取列类型
+    @Override
+    public int getColumnType(int column)
+            throws SQLException
+    {
+        checkColumnIndex(column);
+
+        String columnName = columnNames.get(column - 1);
+        Object value = sampleRow.get(columnName);
+        return MongoTypeHelper.getJdbcType(value);
+    }
+
+    // Get column type name
+    // 获取列类型名称
+    @Override
+    public String getColumnTypeName(int column)
+            throws SQLException
+    {
+        checkColumnIndex(column);
+
+        String columnName = columnNames.get(column - 1);
+        Object value = sampleRow.get(columnName);
+        return MongoTypeHelper.getTypeName(value);
+    }
+
+    // Get column class name
+    // 获取列的Java类名
+    @Override
+    public String getColumnClassName(int column)
+            throws SQLException
+    {
+        checkColumnIndex(column);
+
+        String columnName = columnNames.get(column - 1);
+        Object value = sampleRow.get(columnName);
+        return MongoTypeHelper.getJavaClassName(value);
+    }
+
+    // Check if column is nullable
+    // 检查列是否可为空
+    @Override
+    public int isNullable(int column)
+            throws SQLException
+    {
+        return columnNullable;
+    }
+
+    // Check if column is auto increment
+    // 检查列是否自动递增
+    @Override
+    public boolean isAutoIncrement(int column)
+            throws SQLException
+    {
+        String columnName = getColumnName(column);
+        return columnName.equals("_id");
+    }
+
+    // Check if column is case sensitive
+    // 检查列是否大小写敏感
+    @Override
+    public boolean isCaseSensitive(int column)
+            throws SQLException
+    {
+        return getColumnType(column) == Types.VARCHAR;
+    }
+
+    // Check if column is searchable
+    // 检查列是否可搜索
+    @Override
+    public boolean isSearchable(int column)
+            throws SQLException
+    {
+        return true;
+    }
+
+    // Check if column is currency
+    // 检查列是否货币类型
+    @Override
+    public boolean isCurrency(int column)
+            throws SQLException
+    {
+        return false;
+    }
+
+    // Validate column index
+    // 验证列索引
+    private void checkColumnIndex(int column)
+            throws SQLException
+    {
+        if (column < 1 || column > columnNames.size()) {
+            throw new SQLException("Invalid column index: " + column);
+        }
+    }
+
+    @Override
+    public boolean isSigned(int column)
+            throws SQLException
+    {
+        int type = getColumnType(column);
+        return type == Types.INTEGER || type == Types.BIGINT || type == Types.DOUBLE;
+    }
+
+    @Override
+    public int getColumnDisplaySize(int column)
+            throws SQLException
+    {
+        return 0;
+    }
+
+    @Override
+    public int getPrecision(int column)
+            throws SQLException
+    {
+        return 0;
+    }
+
+    @Override
+    public int getScale(int column)
+            throws SQLException
+    {
+        return 0;
+    }
+
+    @Override
+    public String getTableName(int column)
+            throws SQLException
+    {
+        return "";
+    }
+
+    @Override
+    public String getSchemaName(int column)
+            throws SQLException
+    {
+        return "";
+    }
+
+    @Override
+    public String getCatalogName(int column)
+            throws SQLException
+    {
+        return "";
+    }
+
+    @Override
+    public boolean isReadOnly(int column)
+            throws SQLException
+    {
+        return false;
+    }
+
+    @Override
+    public boolean isWritable(int column)
+            throws SQLException
+    {
+        return true;
+    }
+
+    @Override
+    public boolean isDefinitelyWritable(int column)
+            throws SQLException
+    {
+        return true;
+    }
+
+    @Override
+    public <T> T unwrap(Class<T> iface)
+            throws SQLException
+    {
+        if (iface.isAssignableFrom(getClass())) {
+            return iface.cast(this);
+        }
+        throw new SQLException("Cannot unwrap to " + iface.getName());
+    }
+
+    @Override
+    public boolean isWrapperFor(Class<?> iface)
+            throws SQLException
+    {
+        return iface.isAssignableFrom(getClass());
+    }
+}

driver/datacap-driver-mongodb/src/main/java/io/edurt/datacap/driver/MongoStatement.java

@@ -4,6 +4,7 @@
 import com.mongodb.client.MongoCollection;
 import com.mongodb.client.MongoDatabase;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+import io.edurt.datacap.driver.iterable.InMemoryAggregateIterable;
 import io.edurt.datacap.driver.parser.MongoParser;
 import io.edurt.datacap.driver.parser.MongoShowParser;
 import lombok.extern.slf4j.Slf4j;