Modular representations of Loewy length two

Let G be a finite p-group, K a field of characteristic p, and J the radical of the group algebra K[G]. We study modular representations using some new results of the theory of extensions of modules. More precisely, we describe the K[G]-modules M such that J2M=0 and give some properties and isomorphism invariants which allow us to compute the number of isomorphism classes of K[G]-modules M such that dimK(M)=μ(M)