Does libpg-java support passwordless login? [closed]

Question

The following command runs fine, that is, doesn't ask for a password, prints no warnings or errors, and simply provides a DB prompt:

$ psql -U dbuser dbname
psql (8.4.10)
Type "help" for help.

dbname=# 

When trying to generate an ERD out of this DB with SchemaSpy (running as the same host user), it doesn't work:

$ java -jar ~/schemaSpy.jar -dp /usr/share/java/postgresql.jar -t pgsql \
-host localhost -db dbname -u dbuser -o ~/db

Using database properties:
  [/[...]/schemaSpy.jar]/net/sourceforge/schemaspy/dbTypes/pgsql.properties

Failed to connect to database URL [jdbc:postgresql://localhost/dbname]

org.postgresql.util.PSQLException: The server requested password-based
authentication, but no password was provided.

If I try with a blank password (-p ''), it instead prints:

org.postgresql.util.PSQLException: FATAL: password authentication failed for
user "dbuser"

How do I run SchemaSpy on a PostgreSQL database with a DB user that has no password?

I tried changing the pg_hba.conf settings to completely permissive, but it still doesn't work:

$ sudo grep ^local /etc/postgresql/*/main/pg_hba.conf
local   all         postgres                          ident
local   all         all                               trust

Answer 1

Found the answer related to a similar problem with pgAdmin III: Both programs (unlike psql) establish TCP/IP connections rather than Unix socket connections, so the relevant line in /etc/postgresql/*/main/pg_hba.conf is this one, which will result in a password prompt even if the password is empty.

host    all         all         127.0.0.1/32          md5

To fix this, you have to trust connections from localhost, for example with the following line:

host    all         all         127.0.0.1/32          trust

and reload the configuration:

sudo service postgresql reload

Now both SchemaSpy and pgAdmin should be able to connect.