Merge pull request mendix#7429 from mendix/MVM-JSONStringLength9_24_17

Runtime setting for JSON string length in mapping 9.24.17

Author: MarkvanMents

content/en/docs/refguide9/modeling/integration/mapping-documents/import-mappings.md

@@ -95,3 +95,15 @@ Import mappings have the additional option to receive an incoming parameter. The
 To define a parameter for your mapping, click the parameter box and select the data type. You can also drag an entity into the parameter box. 
 
 You can use a parameter as a key or in a microflow to obtain objects. When you use an entity parameter, you can set associations to it. When you use a primitive parameter (string, integer, etc.), you can write the value to an attribute of an object that is being imported.
+
+## 4 Troubleshooting{#troubleshooting}
+
+If you are importing a very long JSON string, the underlying conversion library may not be able to handle it. In this case you will get a message similar to the following:
+
+`com.mendix.systemvideinterfaces.MendixRuntimeException: com.fasterxm1.jackson.core.exc.StreamConstraintsException: String value length (20051112) exceeds the maximum allowed (20000000, from 'StreamReadConstraints.getMaxStringLength()')`
+
+Mendix uses the Jackson Core XML library when performing the import mapping and this [has a limit of 20 million](https://javadoc.io/static/com.fasterxml.jackson.core/jackson-core/2.15.1/com/fasterxml/jackson/core/StreamReadConstraints.html#DEFAULT_MAX_STRING_LEN) characters (in earlier versions 5 million) in the JSON string.
+
+In Mendix version 9.24.17 and above, you can override this using the [mapping.import.MaxJsonReadingLength](/refguide/custom-settings/#mapping.import.MaxJsonReadingLength) custom setting.
+
+Mendix recommends that you only add this setting if you will be getting very long JSON strings as it may result in more memory usage.

content/en/docs/refguide9/runtime/custom-settings/_index.md

@@ -76,6 +76,7 @@ The following custom settings can be configured:
 | <a id="TempPath" href="#TempPath">TempPath</a> | The location of the temporary files. | [deployment folder]\data\tmp |
 | <a id="TrackWebServiceUserLastLogin" href="#TrackWebServiceUserLastLogin">TrackWebServiceUserLastLogin</a> | Defines whether to update the web service user's `LastLogin` field on each login. When this happens a database update query has to be sent and this can have performance consequences on heavy load systems. When this setting is set to false, no database interaction is necessary. | true |
 | <a id="UploadedFilesPath" href="#UploadedFilesPath">UploadedFilesPath</a> | The location of the uploaded files. A valid path can be: `\\FileServer\CustomerPortalFiles`. | [deployment folder]\data\files |
+| <a id="mapping.import.MaxJsonReadingLength" href="#mapping.import.MaxJsonReadingLength">mapping.import.MaxJsonReadingLength</a> | The maximum length of the JSON string received from the remote which can be processed with import mapping. Use this setting when you expect a string which is longer than the default. See [Import Mappings](/refguide/import-mappings/#troubleshooting) for more information. <br />*This setting was introduced in Mendix version 9.24.17.* | 20000000 *(dependent on library version)* |
 
 ## 3 Log File Settings