## First Steps { #first-steps }

Let's see a very simple example. It will be so simple that it is not very useful, for now.

But this way we can focus on how the **Dependency Injection** system works.

### Create a dependency, or "dependable" { #create-a-dependency-or-dependable }

Let's first focus on the dependency.

	}
	return name
}

// getHandlerName returns the name of the handler function. It takes the type
// name as a string to clean up the name retrieved via reflection. This function
// only works correctly when the type is present in the cmd package.
func getHandlerName(f http.HandlerFunc, cmdType string) string {
	name := runtime.FuncForPC(reflect.ValueOf(f).Pointer()).Name()

And of course, it supports the same:

* data validation
* data serialization
* data documentation, etc.

This works the same way as with Pydantic models. And it is actually achieved in the same way underneath, using Pydantic.

/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

	SHLL	CX, R12
	SHLL	CX, foo+4(SB)
	// Old syntax, still accepted:
	SHLL	CX, R11:AX // SHLL CX, AX, R11

// LTYPEM spec6	{ outcode($1, &$2); }
	MOVL	AX, R11
	MOVL	$4, R11
//	MOVL	AX, 0(AX):DS // no longer works - did it ever?

// LTYPEI spec7	{ outcode($1, &$2); }
	IMULB	DX
	IMULW	DX, BX
	IMULL	R11, R12
	IMULQ	foo+4(SB), R11

// LTYPEXC spec8	{ outcode($1, &$2); }
	CMPPD	X1, X2, 4
	CMPPD	foo+4(SB), X2, 4

    @Override
    public void tearDown() throws Exception {
        ComponentUtil.setFessConfig(null);
        super.tearDown();
    }

    public void test_constructor() {
        // Test that constructor works properly
        assertNotNull(new LtrQueryRescorer());
    }

    public void test_evaluate_withBlankModelName() {
        // Test when model name is blank
        ComponentUtil.setFessConfig(new FessConfig.SimpleImpl() {

            BufferCache.releaseBuffer(tooLarge);
            BufferCache.releaseBuffer(empty);
        });

        // Then - Invalid buffers should be silently ignored
        // Get a new buffer to verify cache still works
        byte[] validBuffer = BufferCache.getBuffer();
        assertNotNull(validBuffer, "Cache should still work after invalid releases");

And an `APIRoute` subclass to use that custom request class.

### Create a custom `GzipRequest` class { #create-a-custom-gziprequest-class }

/// tip

This is a toy example to demonstrate how it works, if you need Gzip support, you can use the provided [`GzipMiddleware`](../advanced/middleware.md#gzipmiddleware){.internal-link target=_blank}.

///

          public <T extends @Nullable Object> T[] toArray(T[] array) {
            T[] result = super.toArray(array);
            if (size() < result.length) {
              // It works around a GWT bug where elements after last is not
              // properly null'ed.
              @Nullable Object[] unsoundlyCovariantArray = result;
              unsoundlyCovariantArray[size()] = null;
            }

      fail("setValue on unmodifiable Map.Entry succeeded");
    } catch (UnsupportedOperationException expected) {
    }
  }

  /**
   * Verifies that an Iterator is unmodifiable.
   *
   * <p>This test only works with iterators that iterate over a finite set.
   */
  public static void assertIteratorIsUnmodifiable(Iterator<?> iterator) {
    while (iterator.hasNext()) {
      iterator.next();
      try {
        iterator.remove();

      byte[] got = out.toByteArray();
      for (int i = 0; i < expected.length; i++) {
        assertEquals(expected[i], got[i]);
      }
    }
  }

  // Assumes that AbstractNonStreamingHashFunction works properly (must be tested elsewhere!)
  private static class Control extends AbstractNonStreamingHashFunction {
    @Override
    public HashCode hashBytes(byte[] input, int off, int len) {