如何使用 PicoContainer 管理动态依赖关系？

发布于 2024-07-19 08:09:37 字数 1140 浏览 7 评论 0原文

假设我有两个类 A 和 B，其中 B 依赖于 A。

public class A {}

public class B {
    public B(A a) {}
}

在单个 PicoContainer 中解析 B 很容易。

    final MutablePicoContainer root = new PicoBuilder().build();
    root.addComponent(new A());
    root.addComponent(B.class, B.class);
    System.out.println(root.getComponent(B.class));

但我希望为不同的会话拥有不同的 B 实例，以及 A 的变量实例。我正在考虑这样的事情。

    // during startup
    final MutablePicoContainer root = new PicoBuilder().build();
    root.addComponent(B.class, B.class);

    // later, initialize sessions
    final MutablePicoContainer session = new PicoBuilder(root)
        .implementedBy(TransientPicoContainer.class)
        .build();
    session.addComponent(new A());

    // some request
    System.out.println(session.getComponent(B.class));

上面的代码不起作用，因为当向 session 请求 B 时，它会向父容器 root 请求它。在那里找到了 B，但仅在 root 及其父级中解析，导致 UnsatisfiableDependencyException。

有什么好的方法可以实现此功能吗？或者这是一种反模式，而我正在以错误的方式解决问题？

原文

Say I have two classes A and B, with B depending on A.

public class A {}

public class B {
    public B(A a) {}
}

It's easy to resolve B in a single PicoContainer.

    final MutablePicoContainer root = new PicoBuilder().build();
    root.addComponent(new A());
    root.addComponent(B.class, B.class);
    System.out.println(root.getComponent(B.class));

But I'd like to have different instances of B for different sessions, with variable instances of A. I'm thinking about something like this.

    // during startup
    final MutablePicoContainer root = new PicoBuilder().build();
    root.addComponent(B.class, B.class);

    // later, initialize sessions
    final MutablePicoContainer session = new PicoBuilder(root)
        .implementedBy(TransientPicoContainer.class)
        .build();
    session.addComponent(new A());

    // some request
    System.out.println(session.getComponent(B.class));

Above code isn't working, because when asking session for a B it asks the parent container root for it. B is found there, but resolved only within root and its parents, leading to an UnsatisfiableDependenciesException.

Is there any good way to make this work? Or is this an anti-pattern, and I'm solving the problem in the wrong way?

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千鲤 2024-07-26 08:09:38

我也会在会话容器中注册 B。您可以将 B 的任何其他依赖项保留在根容器中。假设 B 对 C 有另一个依赖项。因此您可以执行以下操作：

// during startup
final MutablePicoContainer root = new PicoBuilder().build();
root.addComponent(C.class, C.class);

// later, initialize sessions
final MutablePicoContainer session = new PicoBuilder(root)
    .implementedBy(TransientPicoContainer.class)
    .build();
session.addComponent(B.class, B.class);
session.addComponent(new A());

// some request
System.out.println(session.getComponent(B.class));

I would register B within the session container as well. Any other dependency of B you can leave in the root container. Assume B has another dependency on C. So you can do the following:

// during startup
final MutablePicoContainer root = new PicoBuilder().build();
root.addComponent(C.class, C.class);

// later, initialize sessions
final MutablePicoContainer session = new PicoBuilder(root)
    .implementedBy(TransientPicoContainer.class)
    .build();
session.addComponent(B.class, B.class);
session.addComponent(new A());

// some request
System.out.println(session.getComponent(B.class));

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