fix jdbc compatible pre-delivery statements error inner 2212

src/main/java/com/actiontech/dble/backend/mysql/nio/handler/RwSplitSelectVariablesHandler.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2016-2021 ActionTech.
+ * License: http://www.gnu.org/licenses/gpl.html GPL version 2 or higher.
+ */
+
+package com.actiontech.dble.backend.mysql.nio.handler;
+
+import com.actiontech.dble.net.mysql.CharsetNames;
+import com.actiontech.dble.net.mysql.FieldPacket;
+import com.actiontech.dble.net.mysql.RowDataPacket;
+import com.actiontech.dble.net.service.AbstractService;
+import com.actiontech.dble.services.rwsplit.Callback;
+import com.actiontech.dble.services.rwsplit.RWSplitHandler;
+import com.actiontech.dble.services.rwsplit.RWSplitService;
+import com.actiontech.dble.util.StringUtil;
+
+import java.util.*;
+
+public class RwSplitSelectVariablesHandler extends RWSplitHandler {
+    private CharsetNames charsetName;
+    private List<String> columnNames = new ArrayList<>();
+
+    public RwSplitSelectVariablesHandler(RWSplitService service, boolean isUseOriginPacket, byte[] originPacket, Callback callback) {
+        super(service, isUseOriginPacket, originPacket, callback);
+        charsetName = service.getCharset();
+    }
+
+    @Override
+    public void fieldEofResponse(byte[] header, List<byte[]> fields, List<FieldPacket> fieldPacketsNull, byte[] eof,
+                                 boolean isLeft, AbstractService service) {
+        for (byte[] field : fields) {
+            FieldPacket fieldPacket = new FieldPacket();
+            fieldPacket.read(field);
+            String columnName = StringUtil.decode(fieldPacket.getName(), charsetName.getResults());
+            columnNames.add(columnName);
+        }
+        super.fieldEofResponse(header, fields, fieldPacketsNull, eof, isLeft, service);
+    }
+
+    @Override
+    public boolean rowResponse(byte[] row, RowDataPacket rowPacket, boolean isLeft, AbstractService service) {
+        int index = columnNames.size();
+        RowDataPacket rowDataPacket = new RowDataPacket(index);
+        String charset = charsetName.getResults();
+        rowDataPacket.read(row);
+        Map<String, String> variables = getVariables();
+        for (int i = 0; i < index; i++) {
+            String columnName = columnNames.get(i);
+            if (variables.containsKey(columnName)) {
+                rowDataPacket.setValue(i, StringUtil.encode(variables.get(columnName), charset));
+            }
+        }
+        return super.rowResponse(rowDataPacket.toBytes(), rowPacket, isLeft, service);
+    }
+
+    private Map<String, String> getVariables() {
+        Map<String, String> variables = new HashMap<>();
+        variables.put("character_set_client", charsetName.getClient());
+        variables.put("collation_connection", charsetName.getCollation());
+        variables.put("character_set_results", charsetName.getResults());
+        variables.put("character_set_connection", charsetName.getCollation());
+        return variables;
+    }
+}

src/main/java/com/actiontech/dble/rwsplit/RWSplitNonBlockingSession.java

@@ -9,6 +9,7 @@
 import com.actiontech.dble.backend.datasource.PhysicalDbGroup;
 import com.actiontech.dble.backend.datasource.PhysicalDbInstance;
 import com.actiontech.dble.backend.mysql.ByteUtil;
+import com.actiontech.dble.backend.mysql.nio.handler.RwSplitSelectVariablesHandler;
 import com.actiontech.dble.config.ErrorCode;
 import com.actiontech.dble.config.model.SystemConfig;
 import com.actiontech.dble.config.util.ConfigException;
@@ -219,6 +220,38 @@ private boolean isWriteStatistical(boolean writeStatistical) {
         return writeStatistical;
     }
 
+    /**
+     * jdbc compatible pre-delivery statements
+     * @param master
+     * @param originPacket
+     * @param callback
+     * @param writeStatistical
+     * @param localRead
+     */
+    public void selectCompatibilityVariables(Boolean master, byte[] originPacket, Callback callback, boolean writeStatistical, boolean localRead) {
+        try {
+            RWSplitHandler handler = getRwSplitSelectVariablesHandler(originPacket != null ? originPacket : getService().getExecuteSqlBytes(), callback);
+            if (handler == null) return;
+            getConnection(handler, master, isWriteStatistical(writeStatistical), localRead);
+        } catch (SQLSyntaxErrorException | IOException se) {
+            rwSplitService.writeErrMessage(ErrorCode.ER_UNKNOWN_ERROR, se.getMessage());
+        }
+    }
+
+    @Nullable
+    private RWSplitHandler getRwSplitSelectVariablesHandler(byte[] originPacket, Callback callback) throws SQLSyntaxErrorException, IOException {
+        if (conn != null && !conn.isClosed()) {
+            if (LOGGER.isDebugEnabled()) {
+                LOGGER.debug("select bind conn[id={}]", conn.getId());
+            }
+            RWSplitHandler handler = new RwSplitSelectVariablesHandler(rwSplitService, true, originPacket, callback);
+            checkDest(!conn.getInstance().isReadInstance());
+            handler.execute(conn);
+            return null;
+        }
+        return new RwSplitSelectVariablesHandler(rwSplitService, true, originPacket, callback);
+    }
+
     private Boolean canRunOnMaster(Boolean master) {
         if ((rwSplitService.isInTransaction() && !rwSplitService.isReadOnly()) || rwSplitService.isUsingTmpTable()) {
             return true;

src/main/java/com/actiontech/dble/services/rwsplit/handle/RwSplitSelectHandler.java

@@ -6,7 +6,6 @@
 package com.actiontech.dble.services.rwsplit.handle;
 
 import com.actiontech.dble.server.parser.RwSplitServerParseSelect;
-import com.actiontech.dble.server.response.SelectVariables;
 import com.actiontech.dble.services.rwsplit.RWSplitService;
 
 
@@ -20,7 +19,7 @@ private RwSplitSelectHandler() {
     public static void handle(String stmt, RWSplitService service, int offset) {
         switch (RwSplitServerParseSelect.parse(stmt, offset)) {
             case RwSplitServerParseSelect.SELECT_VAR_ALL:
-                SelectVariables.execute(service, stmt);
+                service.getSession2().selectCompatibilityVariables(true, null, null, false, false);
                 break;
             default: {
                 int rs2 = RwSplitServerParseSelect.parseSpecial(stmt);