[jira] [Updated] (NIFI-9169) Improvement for Expression Language when evaluated result is NULL

[ZhangCheng (Jira)]

     [ 
https://issues.apache.org/jira/browse/NIFI-9169?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

ZhangCheng updated NIFI-9169:
-----------------------------
    Description: 
For NIFI, If we set some EL to one processor, such as `${schema.name}` for 
PutDatabaseREcord, and the incoming flowfile does not have a `schema.name` 
attribute, then the result of PutDatabaseRecord property evalutes is Empty 
String(""), not NULL.
{code:java}
        if (expressions.size() == 1) {
            final String evaluated = 
expressions.get(0).evaluate(evaluationContext, decorator);
            return evaluated == null ? EMPTY_STRING : evaluated;
        }
{code}

And maybe we don not want the Empty String , for example

{code:java}
// PutDatabaseRecord 
public static TableSchema from(final Connection conn, final String catalog, 
final String schema, final String tableName,
                                       final boolean translateColumnNames, 
final boolean includePrimaryKeys, ComponentLog log) throws SQLException {
            final DatabaseMetaData dmd = conn.getMetaData();

            try (final ResultSet colrs = dmd.getColumns(catalog, schema, 
tableName, "%")) {
.......
{code}






> Improvement for Expression Language when evaluated result is NULL
> -----------------------------------------------------------------
>
>                 Key: NIFI-9169
>                 URL: https://issues.apache.org/jira/browse/NIFI-9169
>             Project: Apache NiFi
>          Issue Type: Improvement
>            Reporter: ZhangCheng
>            Assignee: ZhangCheng
>            Priority: Major
>
> For NIFI, If we set some EL to one processor, such as `${schema.name}` for 
> PutDatabaseREcord, and the incoming flowfile does not have a `schema.name` 
> attribute, then the result of PutDatabaseRecord property evalutes is Empty 
> String(""), not NULL.
> {code:java}
>         if (expressions.size() == 1) {
>             final String evaluated = 
> expressions.get(0).evaluate(evaluationContext, decorator);
>             return evaluated == null ? EMPTY_STRING : evaluated;
>         }
> {code}
> And maybe we don not want the Empty String , for example
> {code:java}
> // PutDatabaseRecord 
> public static TableSchema from(final Connection conn, final String catalog, 
> final String schema, final String tableName,
>                                        final boolean translateColumnNames, 
> final boolean includePrimaryKeys, ComponentLog log) throws SQLException {
>             final DatabaseMetaData dmd = conn.getMetaData();
>             try (final ResultSet colrs = dmd.getColumns(catalog, schema, 
> tableName, "%")) {
> .......
> {code}



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