What do they often say about middleware? How do we understand the middleware here?

What do they often say about middleware? How do we understand the middleware here? What do they often say about middleware? How do we understand the middleware here?

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What do they often say about middleware? How do we understand the middleware here?

In fact, many things can be called middleware, as long as it connects up and down two layers of systems through interfaces

For example, the RPC call component you use can be called middleware, because it connects the RPC service and the client
For example, the Server Load balancer proxy of the database accesses this proxy, which calls the database

It can be understood as middleware for inter-system transmission and connection, such as mima, hessian, and hsf.