I have the following situation : Project A - Contains a few entities and is independent Project B - Contains a few entities and is independent Project C - Contains few entities and is dependent on Project A & Project B. I am using Maven to manage dependencies and builds. When I try to test Project A and project B it goes through fine. Each of them has a persistence.xml and a separate persistent context. When I run Project C , It does map any of the entities. I have tried to use the auto-detect, specified the jar file attribute ... but nothing seems to work. It gives me a Mapping Exception saying unknown entity and wont persist or read the Entities from Projects A or B. I have posted the 3 persistence.xml files here. Also, I tried using the class attribute and using the same persistent context but it just wont find the files. Any help is really appreciated. Thanks in advance ! <persistence 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" version="1.0"> <persistence-unit name="A" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle9Dialect"/> <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.connection.username" value="username"/> <property name="hibernate.connection.password" value="password"/> <property name="hibernate.connection.url" value="jdbc:oracle:thin:@webdev.epi.web:1521/webdev.world"/> <property name="hibernate.max_fetch_depth" value="3"/> <property name="hibernate.archive.autodetection" value="class"/> </properties> </persistence-unit> </persistence> <persistence 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" version="1.0"> <persistence-unit name="B" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle9Dialect"/> <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.connection.username" value="username"/> <property name="hibernate.connection.password" value="password"/> <property name="hibernate.connection.url" value="jdbc:oracle:thin:@webdev.epi.web:1521/webdev.world"/> <property name="hibernate.max_fetch_depth" value="3"/> <property name="hibernate.archive.autodetection" value="class"/> </properties> </persistence-unit> </persistence> <persistence 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" version="1.0"> <persistence-unit name="C" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <jar-file>A-0.0.1-SNAPSHOT.jar</jar-file> <jar-file>B-0.0.1-SNAPSHOT.jar</jar-file> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle9Dialect"/> <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.connection.username" value="username"/> <property name="hibernate.connection.password" value="password"/> <property name="hibernate.connection.url" value="jdbc:oracle:thin:@webdev.epi.web:1521/webdev.world"/> <property name="hibernate.max_fetch_depth" value="3"/> <property name="hibernate.archive.autodetection" value="class"/> </properties> </persistence-unit> </persistence>