{* ../../docs_src/openapi_callbacks/tutorial001.py hl[3,25] *}

### Create the callback *path operation* { #create-the-callback-path-operation }

To create the callback *path operation* use the same `APIRouter` you created above.

It should look just like a normal FastAPI *path operation*:

* It should probably have a declaration of the body it should receive, e.g. `body: InvoiceEvent`.

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.math.BigInteger;
import org.jspecify.annotations.Nullable;

/**
 * A wrapper class for unsigned {@code long} values, supporting arithmetic operations.
 *
 * <p>In some cases, when speed is more important than code readability, it may be faster simply to
 * treat primitive {@code long} values as unsigned, using the methods from {@link UnsignedLongs}.
 *

<img src="/img/tutorial/body/image03.png">

You also get error checks for incorrect type operations:

<img src="/img/tutorial/body/image04.png">

This is not by chance, the whole framework was built around that design.

And it was thoroughly tested at the design phase, before any implementation, to ensure it would work with all the editors.

import java.util.Objects;
import junit.framework.TestCase;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Test cases for {@link Table} read operations.
 *
 * @author Jared Levy
 */
@GwtCompatible
@NullMarked
public abstract class AbstractTableReadTest<C extends @Nullable Character> extends TestCase {
  protected Table<String, Integer, C> table;

  /**

 *
 * <p>The simplest use case is:
 *
 * <pre>
 * new EqualsTester().addEqualityGroup(foo).testEquals();
 * </pre>
 *
 * <p>This tests {@code foo.equals(foo)}, {@code foo.equals(null)}, and a few other operations.
 *
 * <p>For more extensive testing, add multiple equality groups. Each group should contain objects
 * that are equal to each other but unequal to the objects in any other group. For example:
 *
 * <pre>

import java.nio.charset.Charset;
import java.util.Properties;

import org.codelibs.core.exception.IORuntimeException;
import org.codelibs.core.net.URLUtil;

/**
 * Utility class for {@link Properties} operations.
 *
 * @author higa
 */
public abstract class PropertiesUtil {

    /**
     * Do not instantiate.
     */
    protected PropertiesUtil() {
    }

    /**

 *
 * <p>The simplest use case is:
 *
 * <pre>
 * new EqualsTester().addEqualityGroup(foo).testEquals();
 * </pre>
 *
 * <p>This tests {@code foo.equals(foo)}, {@code foo.equals(null)}, and a few other operations.
 *
 * <p>For more extensive testing, add multiple equality groups. Each group should contain objects
 * that are equal to each other but unequal to the objects in any other group. For example:
 *
 * <pre>

import jcifs.smb.SmbException;

/**
 * SMB1 Session Setup AndX request message.
 *
 * This command is used to authenticate a user session and
 * establish security context for subsequent operations.
 */
public class SmbComSessionSetupAndX extends AndXServerMessageBlock {

    private byte[] lmHash, ntHash, blob = null;
    private String accountName, primaryDomain;

            } finally {
                this.next = null;
                this.treeHandle.release();
            }
        }
    }

    /**
     * Performs the internal closing operations specific to the implementation.
     *
     * @throws CIFSException if an error occurs during internal closing
     */
    protected abstract void doCloseInternal() throws CIFSException;

    /**

            assertTrue(result.startsWith("Transport"));
            assertFalse(result.isEmpty());
        }

        @Test
        @DisplayName("should handle response map operations")
        void shouldHandleResponseMapOperations() {
            assertEquals(0, transport.getResponseMapSize());
            // Response map is accessible through protected field for testing