Fixed a bug where calling length() after obtaining a stream would clo…

…se the stream for Clobs/NClobs (#799)

Addresses #788. Also addressed an issue where varchar(max)/Clob objects were always being encoded to UTF-16LE instead of using the Collation specified in the Clob object.

List of Changes (the following applies to NClob as well):

1. calling Clob.length() no longer attempts to load the stream into a string. This fixes a null pointer issue as well as length() closing user streams.
2. added streaming capabilities for Clob.getAsciiStream(). NClobs will always have a non-streaming implementation for getAsciiStream().
3. Clobs no longer default to UTF-16LE. Clobs now respect the collation from the SQL Server. NClobs remain unchanged, will always be UTF-16LE encoding.

src/main/java/com/microsoft/sqlserver/jdbc/PLPInputStream.java

@@ -25,9 +25,6 @@ class PLPInputStream extends BaseInputStream {
     static final int PLP_TERMINATOR = 0x00000000;
     private final static byte[] EMPTY_PLP_BYTES = new byte[0];
 
-    // Stated length of the PLP stream payload; -1 if unknown length.
-    int payloadLength;
-
     private static final int PLP_EOS = -1;
     private int currentChunkRemain;
 

src/main/java/com/microsoft/sqlserver/jdbc/SQLServerClob.java

@@ -5,11 +5,9 @@
 
 package com.microsoft.sqlserver.jdbc;
 
-import static java.nio.charset.StandardCharsets.US_ASCII;
-import static java.nio.charset.StandardCharsets.UTF_16LE;
-
 import java.io.BufferedInputStream;
 import java.io.BufferedReader;
+import java.io.ByteArrayInputStream;
 import java.io.Closeable;
 import java.io.IOException;
 import java.io.InputStream;
@@ -20,6 +18,7 @@
 import java.io.StringReader;
 import java.io.UnsupportedEncodingException;
 import java.io.Writer;
+import java.nio.charset.Charset;
 import java.sql.Clob;
 import java.sql.SQLException;
 import java.text.MessageFormat;
@@ -152,7 +151,7 @@ abstract class SQLServerClobBase extends SQLServerLob implements Serializable {
 
     // The value of the CLOB that this Clob object represents.
     // This value is never null unless/until the free() method is called.
-    private String value;
+    protected String value;
 
     private final SQLCollation sqlCollation;
 
@@ -181,8 +180,9 @@ final public String toString() {
     // Unique id generator for each instance (used for logging).
     static private final AtomicInteger baseID = new AtomicInteger(0);
 
+    private Charset defaultCharset = null;
+
     // Returns unique id for each instance.
-
     private static int nextInstanceID() {
         return baseID.incrementAndGet();
     }
@@ -281,9 +281,19 @@ public InputStream getAsciiStream() throws SQLException {
         if (null != sqlCollation && !sqlCollation.supportsAsciiConversion())
             DataTypes.throwConversionError(getDisplayClassName(), "AsciiStream");
 
-        getStringFromStream();
-        InputStream getterStream = new BufferedInputStream(
-                new ReaderInputStream(new StringReader(value), US_ASCII, value.length()));
+        // Need to use a BufferedInputStream since the stream returned by this method is assumed to support mark/reset
+        InputStream getterStream = null;
+        if (null == value && !activeStreams.isEmpty()) {
+            InputStream inputStream = (InputStream) activeStreams.get(0);
+            try {
+                inputStream.reset();
+            } catch (IOException e) {
+                SQLServerException.makeFromDriverError(con, null, e.getMessage(), null, false);
+            }
+            getterStream = new BufferedInputStream(inputStream);
+        } else {
+            getterStream = new ByteArrayInputStream(value.getBytes(java.nio.charset.StandardCharsets.US_ASCII));
+        }
         activeStreams.add(getterStream);
         return getterStream;
     }
@@ -301,11 +311,17 @@ public Reader getCharacterStream() throws SQLException {
         Reader getterStream = null;
         if (null == value && !activeStreams.isEmpty()) {
             InputStream inputStream = (InputStream) activeStreams.get(0);
-            getterStream = new BufferedReader(new InputStreamReader(inputStream, UTF_16LE));
+            try {
+                inputStream.reset();
+            } catch (IOException e) {
+                SQLServerException.makeFromDriverError(con, null, e.getMessage(), null, false);
+            }
+            Charset cs = (defaultCharset == null) ? typeInfo.getCharset() : defaultCharset;
+            getterStream = new BufferedReader(new InputStreamReader(inputStream, cs));
         } else {
             getterStream = new StringReader(value);
-            activeStreams.add(getterStream);
         }
+        activeStreams.add(getterStream);
         return getterStream;
     }
 
@@ -381,9 +397,8 @@ public String getSubString(long pos, int length) throws SQLException {
      */
     public long length() throws SQLException {
         checkClosed();
-
-        if (value == null && activeStreams.get(0) instanceof PLPInputStream) {
-            return (long) ((PLPInputStream) activeStreams.get(0)).payloadLength / 2;
+        if (null == value && activeStreams.get(0) instanceof BaseInputStream) {
+            return (long) ((BaseInputStream) activeStreams.get(0)).payloadLength;
         }
         return value.length();
     }
@@ -410,9 +425,10 @@ private void getStringFromStream() throws SQLServerException {
             try {
                 stream.reset();
             } catch (IOException e) {
-                throw new SQLServerException(e.getMessage(), null, 0, e);
+                SQLServerException.makeFromDriverError(con, null, e.getMessage(), null, false);
             }
-            value = new String((stream).getBytes(), typeInfo.getCharset());
+            Charset cs = (defaultCharset == null) ? typeInfo.getCharset() : defaultCharset;
+            value = new String(stream.getBytes(), cs);
         }
     }
 
@@ -661,6 +677,10 @@ public int setString(long pos, String str, int offset, int len) throws SQLExcept
 
         return len;
     }
+
+    protected void setDefaultCharset(Charset c) {
+        this.defaultCharset = c;
+    }
 }
 
 

src/main/java/com/microsoft/sqlserver/jdbc/SQLServerNClob.java

@@ -32,10 +32,12 @@ public final class SQLServerNClob extends SQLServerClobBase implements NClob {
 
     SQLServerNClob(SQLServerConnection connection) {
         super(connection, "", connection.getDatabaseCollation(), logger, null);
+        this.setDefaultCharset(java.nio.charset.StandardCharsets.UTF_16LE);
     }
 
     SQLServerNClob(BaseInputStream stream, TypeInfo typeInfo) throws SQLServerException, UnsupportedEncodingException {
         super(null, stream, typeInfo.getSQLCollation(), logger, typeInfo);
+        this.setDefaultCharset(java.nio.charset.StandardCharsets.UTF_16LE);
     }
 
     @Override
@@ -45,6 +47,9 @@ public void free() throws SQLException {
 
     @Override
     public InputStream getAsciiStream() throws SQLException {
+        // NClobs are mapped to Nvarchar(max), and are always UTF-16 encoded. This API expects a US_ASCII stream.
+        // It's not possible to modify the stream without loading it into memory. Users should use getCharacterStream.
+        this.fillFromStream();
         return super.getAsciiStream();
     }
 
@@ -65,7 +70,9 @@ public String getSubString(long pos, int length) throws SQLException {
 
     @Override
     public long length() throws SQLException {
-        return super.length();
+        // If streaming, every 2 bytes represents 1 character. If not, length() just returns string length
+        long length = super.length();
+        return (null == value) ? length / 2 : length;
     }
 
     @Override

src/main/java/com/microsoft/sqlserver/jdbc/SimpleInputStream.java

@@ -24,6 +24,9 @@ abstract class BaseInputStream extends InputStream {
 
     // Flag indicating whether the stream consumes and discards data as it reads it
     final boolean isStreaming;
+
+    // Stated length of the payload
+    int payloadLength;
 
     /** Generate the logging ID */
     private String parentLoggingInfo = "";
@@ -131,9 +134,6 @@ void resetHelper() throws IOException {
 
 final class SimpleInputStream extends BaseInputStream {
 
-    // Stated length of the payload
-    private final int payloadLength;
-
     /**
      * Initializes the input stream.
      */