<?xml version="1.0" encoding="UTF-8"?>
<Context>
<Manager pathname="" />
<Resource auth="Container" driverClassName="org.postgresql.Driver"   maxActive="20" maxIdle="5" maxWait="10000" name="jdbc/custom" password="CHANGEIT" type="javax.sql.DataSource" url="jdbc:postgresql://10.10.10.10:5432/database" username="MyUser"/>
</Context>

# It's OK
sed 's/(.*password=)[^ ]*( .*)/1"NEW_VALUE"2/' ROOT.xml

# It's NOK
sed 's/(.*username=)[^ ]*( .*)/1"NEW_VALUE"2/' ROOT.xml