*
     * @return a string representing the source of the options
     */
    @Nonnull
    String source();

    /**
     * Returns the user-defined properties for the Maven execution.
     *
     * @return an {@link Optional} containing the map of user properties, or empty if not set
     */
    @Nonnull
    Optional<Map<String, String>> userProperties();

    /**

import static com.google.common.util.concurrent.MoreExecutors.shutdownAndAwaitTermination;
import static com.google.common.util.concurrent.Uninterruptibles.awaitUninterruptibly;
import static java.util.concurrent.Executors.newSingleThreadExecutor;
import static java.util.concurrent.TimeUnit.SECONDS;
import static org.junit.Assert.assertThrows;

import com.google.common.util.concurrent.ClosingFuture.ClosingCallable;

 * possibly run in another thread. That cause should itself be an {@code Error}; if not, use {@code
 * ExecutionException} or {@link UncheckedExecutionException}. This allows the client code to
 * continue to distinguish between exceptions and errors, even when they come from other threads.
 *
 * @author Chris Povirk
 * @since 10.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public class ExecutionError extends Error {
  /*

      "/runCase?case=$number&agent=okhttp",
      object : WebSocketListener() {
        override fun onOpen(
          webSocket: WebSocket,
          response: Response,
        ) {
          println("Executing test case $number/$count")
          startNanos.set(System.nanoTime())
        }

        override fun onMessage(
          webSocket: WebSocket,
          bytes: ByteString,
        ) {

/**
 * Defines a simple logging interface for Maven CLI operations.
 * This interface provides methods for logging messages at different severity levels
 * and supports logging with or without associated exceptions.
 *
 * @since 4.0.0
 */
@Experimental
public interface Logger {

    /**
     * Represents the severity levels for log messages.
     */
    enum Level {
        DEBUG,
        INFO,

import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;

from fastapi import FastAPI, HTTPException
from fastapi.testclient import TestClient
from starlette.exceptions import HTTPException as StarletteHTTPException

app = FastAPI()

items = {"foo": "The Foo Wrestlers"}


@app.get("/items/{item_id}")
async def read_item(item_id: str):
    if item_id not in items:
        raise HTTPException(
            status_code=404,
            detail="Item not found",

一般情况下可能不会需要在代码中直接使用响应头。

但对于某些高级应用场景，还是需要添加自定义响应头：

```Python hl_lines="14"
{!../../docs_src/handling_errors/tutorial002.py!}

```

## 安装自定义异常处理器

添加自定义处理器，要使用 [Starlette 的异常工具](https://www.starlette.io/exceptions/)。

假设要触发的自定义异常叫作 `UnicornException`。

且需要 FastAPI 实现全局处理该异常。

此时，可以用 `@app.exception_handler()` 添加自定义异常控制器：

```Python hl_lines="5-7  13-18  24"
{!../../docs_src/handling_errors/tutorial003.py!}

message LimitedPriorityLevelConfiguration {
  // `nominalConcurrencyShares` (NCS) contributes to the computation of the
  // NominalConcurrencyLimit (NominalCL) of this level.
  // This is the number of execution seats available at this priority level.
  // This is used both for requests dispatched from this priority level
  // as well as requests dispatched from other priority levels
  // borrowing seats from this level.

    #     and not-param-result are auto-generated.
    #     And also not-param-result's properties are auto-generated.
    #     Target procedures are executed actually at Sql2Entity task.
    #     (because of getting from execution meta data (result set meta data))
    #     This property is valid only when isGenerateProcedureParameterBean is true.
    #
    ; isGenerateProcedureCustomizeEntity = false
    # - - - - - - - - - -/