Drop JDO support [SPR-14130]

[spring-projects-issues]

Juergen Hoeller opened SPR-14130 and commented

After many years of keeping our orm.jdo package alive, the time seems to be right to finally drop it as of Spring 5. Not only did it never grow beyond a niche feature, it is functionally matched by JPA 2.1 now, even for DataNucleus (the JDO reference implementation) which can nicely be used as a JPA 2.1 provider these days.

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Issue Links:

• Remove native support for Hibernate 3.6 and 4.x [SPR-13827] #18400 Remove native support for Hibernate 3.6 and 4.x
• Drop Portlet MVC support [SPR-14129] #18701 Drop Portlet MVC support

Referenced from: commits d341624