Add specific mybatis string type handler

modules/flowable-engine-common/src/main/java/org/flowable/common/engine/impl/AbstractEngineConfiguration.java

@@ -81,6 +81,7 @@
 import org.flowable.common.engine.impl.cfg.standalone.StandaloneMybatisTransactionContextFactory;
 import org.flowable.common.engine.impl.db.CommonDbSchemaManager;
 import org.flowable.common.engine.impl.db.DbSqlSessionFactory;
+import org.flowable.common.engine.impl.db.FlowableStringTypeHandler;
 import org.flowable.common.engine.impl.db.LogSqlExecutionTimePlugin;
 import org.flowable.common.engine.impl.db.MybatisTypeAliasConfigurator;
 import org.flowable.common.engine.impl.db.MybatisTypeHandlerConfigurator;
@@ -948,8 +949,8 @@ public void initMybatisTypeHandlers(Configuration configuration) {
             // thus the same handler is used for both types.
             handlerRegistry.register(String.class, JdbcType.VARCHAR, new StringTypeHandler());
             handlerRegistry.register(Object.class, JdbcType.VARCHAR, new StringTypeHandler());
-            handlerRegistry.register(String.class, JdbcType.NVARCHAR, new StringTypeHandler()); // Notice: no 'N' prefix here
-            handlerRegistry.register(Object.class, JdbcType.NVARCHAR, new StringTypeHandler()); // Notice: no 'N' prefix here
+            handlerRegistry.register(String.class, JdbcType.NVARCHAR, new FlowableStringTypeHandler()); // Notice: no 'N' prefix here
+            handlerRegistry.register(Object.class, JdbcType.NVARCHAR, new FlowableStringTypeHandler()); // Notice: no 'N' prefix here
         }
 
         handlerRegistry.register(Object.class, JdbcType.LONGVARCHAR, new StringTypeHandler());

modules/flowable-engine-common/src/main/java/org/flowable/common/engine/impl/db/FlowableStringTypeHandler.java

@@ -0,0 +1,59 @@
+package org.flowable.common.engine.impl.db;
+
+import java.sql.CallableStatement;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Types;
+
+import org.apache.ibatis.type.BaseTypeHandler;
+import org.apache.ibatis.type.JdbcType;
+import org.apache.ibatis.type.TypeException;
+
+public class FlowableStringTypeHandler extends BaseTypeHandler<String> {
+
+    @Override
+    public void setParameter(PreparedStatement ps, int i, String parameter, JdbcType jdbcType) throws SQLException {
+      if (parameter == null) {
+        if (jdbcType == null) {
+          throw new TypeException("JDBC requires that the JdbcType must be specified for all nullable parameters.");
+        }
+        try {
+          ps.setNull(i, Types.NULL);
+        } catch (SQLException e) {
+          throw new TypeException("Error setting null for parameter #" + i + " with JdbcType " + jdbcType + " . "
+              + "Try setting a different JdbcType for this parameter or a different jdbcTypeForNull configuration property. "
+              + "Cause: " + e, e);
+        }
+      } else {
+        try {
+          setNonNullParameter(ps, i, parameter, jdbcType);
+        } catch (Exception e) {
+          throw new TypeException("Error setting non null for parameter #" + i + " with JdbcType " + jdbcType + " . "
+              + "Try setting a different JdbcType for this parameter or a different configuration property. " + "Cause: "
+              + e, e);
+        }
+      }
+    }
+
+    @Override
+    public void setNonNullParameter(PreparedStatement ps, int i, String parameter, JdbcType jdbcType)
+        throws SQLException {
+      ps.setString(i, parameter);
+    }
+
+    @Override
+    public String getNullableResult(ResultSet rs, String columnName) throws SQLException {
+      return rs.getString(columnName);
+    }
+
+    @Override
+    public String getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
+      return rs.getString(columnIndex);
+    }
+
+    @Override
+    public String getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
+      return cs.getString(columnIndex);
+    }
+  }