Does Java Postgresql Driver support Array Datatype, getting NullPointerException

Question

Im using Postgres 9.3, I get the Java database driver like this

try {
    Class.forName("org.postgresql.Driver");
} catch (ClassNotFoundException e) {
    System.err.println("Couldn't load org.postgresql.Driver");
    System.exit(1);
}

Then I do :

  Array urlData = rs.getArray("urls");
  String[] urls = (String[]) urlData.getArray();

but last line is failing with NullPointerException because urlData is null

Why is this, is Array not supported for Postgresql, the tutorial does state not supported for Mysql

https://docs.oracle.com/javase/tutorial/jdbc/basics/array.html

Or it is just null because no data for urls for a particular row?

The attempt to use getObject suggested in answer failed with

Exception in thread "main" java.lang.AbstractMethodError: Method org/postgresql/jdbc4/Jdbc4ResultSet.getObject(Ljava/lang/String;Ljava/lang/Class;)Ljava/lang/Object; is abstract
        at org.postgresql.jdbc4.Jdbc4ResultSet.getObject(Jdbc4ResultSet.java)
        at com.jthink.jthinksearch.index.indexer.discogs.ArtistIndex.documentFromResultSet(ArtistIndex.java:209)
        at com.jthink.jthinksearch.index.indexer.discogs.ArtistIndex.indexData(ArtistIndex.java:176)
        at com.jthink.jthinksearch.index.indexer.IndexBuilder.buildDatabaseIndex(IndexBuilder.java:226)
        at com.jthink.jthinksearch.index.indexer.IndexBuilder.buildIndex(IndexBuilder.java:151)
        at com.jthink.jthinksearch.index.indexer.IndexBuilder.main(IndexBuilder.java:119)

The linked tutorial only calls out lack of support for MySQL and Java DB, because those are also Oracle products. It doesn't mean that all other JDBC drivers do support them, although the PostgreSQL driver does support arrays. The AbstractMethodError suggests you are using an old version of the driver (the getObject method you tried was introduced in Java 7 / JDBC 4.1), consider upgrading to a newer version of the PostgreSQL JDBC driver. — Mark Rotteveel
– Mark Rotteveel, Commented Jun 14, 2018 at 17:41
@MarkRotteveel I suggest to use getObject then I removed that because when I try to use String[] urls = rs.getObject("urls", String[].class); I get an error The org.postgresql.jdbc4.Jdbc4ResultSet.getObject (int, Class <T>) function is not yet implemented. I'm using mvnrepository.com/artifact/postgresql/postgresql/… do you have any idea why this error please? I rolledback my solution you can check where it was my mistake maybe — Youcef LAIDANI
– Youcef LAIDANI, Commented Jun 14, 2018 at 18:46
@YCF_L Yes, use a newer version, like version 42.2.2 (eg mvnrepository.com/artifact/org.postgresql/postgresql/42.2.2 ) — Mark Rotteveel
– Mark Rotteveel, Commented Jun 14, 2018 at 19:30
Thank you @MarkRotteveel now with my solution it gives me org.postgresql.util.PSQLException: conversion to class [Ljava.lang.String; from 2 003 not supported — Youcef LAIDANI
– Youcef LAIDANI, Commented Jun 14, 2018 at 19:40

Youcef LAIDANI · Accepted Answer · 2018-06-14 19:44:25Z

2

I suppose because it is just null because no data for urls for a particular field ?

To solve your problem you can use :

Array urlData = rs.getArray("urls");
String[] urls = urlData != null ? (String[]) urlData.getArray() : null;//or a default value

edited Jun 14, 2018 at 19:44

answered Jun 14, 2018 at 15:11

Youcef LAIDANI

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3 Comments

Paul Taylor Over a year ago

Maybe I will try again, but getObjects () failed with exception above, not supported by driver

Youcef LAIDANI Over a year ago

@PaulTaylor yes I already tried my second solution and it seems that implementation of getObject is not yes complete, but you can solve your problem with the first one

Paul Taylor Over a year ago

Thanks you are correct it just failed because there was no data for a row, now working.

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