# Classes as Dependencies { #classes-as-dependencies }

Before diving deeper into the **Dependency Injection** system, let's upgrade the previous example.

## A `dict` from the previous example { #a-dict-from-the-previous-example }

In the previous example, we were returning a `dict` from our dependency ("dependable"):

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Annotates a "top-level" type-variable usage that takes its nullness from the type argument
 * supplied by the user of the class. For example, {@code Multiset.Entry.getElement()} returns
 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Annotates a "top-level" type-variable usage that takes its nullness from the type argument
 * supplied by the user of the class. For example, {@code Multiset.Entry.getElement()} returns
 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.

The `TestClient` is based on <a href="https://www.python-httpx.org" class="external-link" target="_blank">HTTPX</a>, and luckily, we can use it directly to test the API.

## Example { #example }

For a simple example, let's consider a file structure similar to the one described in [Bigger Applications](../tutorial/bigger-applications.md){.internal-link target=_blank} and [Testing](../tutorial/testing.md){.internal-link target=_blank}:

        // Test when only baseDn is set
        ComponentUtil.setFessConfig(new FessConfig.SimpleImpl() {
            @Override
            public String getLdapBaseDn() {
                return "dc=example,dc=com";
            }

            @Override
            public String getLdapAccountFilter() {
                return "";
            }
        });

        // Test registerSmbURLHandler when java.protocol.handler.pkgs does not contain "jcifs"
        System.setProperty("java.protocol.handler.pkgs", "com.example");
        SingletonContext.registerSmbURLHandler();
        assertEquals("com.example|jcifs", System.getProperty("java.protocol.handler.pkgs"));
    }

    @Test
    void testRegisterSmbURLHandlerWhenPkgsAlreadyContainsJcifs() {

    @Mock
    private CredentialsInternal credentialsInternal;
    @Mock
    private SmbTransportImpl transport;

    private SmbSessionImpl newSession() {
        return new SmbSessionImpl(cifsContext, "server.example", "EXAMPLE", transport);
    }

    @BeforeEach
    void setup() {
        // Base context configuration - always needed
        when(cifsContext.getConfig()).thenReturn(configuration);

import javax.security.auth.callback.UnsupportedCallbackException
import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.internal.SuppressSignatureCheck
import okhttp3.internal.platform.Platform

/**
 * Example of using a hardware key to perform client auth.
 * Prefer recent JDK builds, and results are temperamental to slight environment changes.
 * Different instructions and configuration may be required for other hardware devices.
 *

In this example, when the client requests an item by an ID that doesn't exist, raise an exception with a status code of `404`:

{* ../../docs_src/handling_errors/tutorial001.py hl[11] *}

### The resulting response { #the-resulting-response }

This document focuses on showing a working example on how to use Object Lambda with MinIO, you must have [MinIO deployed in your environment](https://docs.min.io/community/minio-object-store/operations/installation.html) before you can start using external lambda functions. You also must install Python version 3.8 or later for the lambda handlers to work.

## Example Lambda handler

Install the necessary dependencies.
```sh