How to get rid of 'java.lang.IllegalArgumentException: Unknown entity' while running a simple hibernate app?

Depends bit about project structure, but likely by adding following to persistence.xml directly under persistence-unit element.

<class>model.Students</class>
<class>model.Address</class>

Exactly like this:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence"     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"     xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
  <persistence-unit name="OneToOnePU" transaction-type="JTA">
    <provider>org.hibernate.ejb.HibernatePersistence</provider>

    <jta-data-source>students</jta-data-source>
    <class>model.Students</class>
    <class>model.Address</class>
    <exclude-unlisted-classes>false</exclude-unlisted-classes>
    <properties>
      <property name="hibernate.hbm2ddl.auto" value="create-tables"/>
      <property name="hibernate.dialect" value="org.hibernate.dialect.DerbyDialect"/>
      <property name="hibernate.connection.username" value="app"/>
      <property name="hibernate.connection.password" value="app"/>
      <property name="hibernate.connection.url" value="jdbc:derby://localhost:1527/StudentsData"/>
    </properties>
  </persistence-unit>
</persistence>

By the way, why do you configure properties like hibernate.dialect in both persistence.xml and hibernate.cfg.xml?

I'm Trying this and it's working with me :

Add @EntityScan( basePackages = {"com.yourpkghere"} to Application class. To be like this :

@EntityScan( basePackages = {"com.yourpkghere"})
@SpringBootApplication