## Install custom exception handlers { #install-custom-exception-handlers }

You can add custom exception handlers with [the same exception utilities from Starlette](https://www.starlette.dev/exceptions/).

Let's say you have a custom exception `UnicornException` that you (or a library you use) might `raise`.

And you want to handle this exception globally with FastAPI.

You could add a custom exception handler with `@app.exception_handler()`:

    - topic_repos: ../en/data/topic_repos.yml
  redirects:
    redirect_maps:
      deployment/deta.md: deployment/cloud.md
      advanced/graphql.md: how-to/graphql.md
      advanced/custom-request-and-route.md: how-to/custom-request-and-route.md
      advanced/conditional-openapi.md: how-to/conditional-openapi.md
      advanced/extending-openapi.md: how-to/extending-openapi.md

        "uid": "${DS_PROMETHEUS}"
      },
      "description": "",
      "fieldConfig": {
        "defaults": {
          "color": {
            "mode": "palette-classic"
          },
          "custom": {
            "axisBorderShow": false,
            "axisCenteredZero": false,
            "axisColorMode": "text",
            "axisLabel": "",
            "axisPlacement": "auto",
            "barAlignment": 0,

- **Features**: JavaScript rendering, authentication, custom headers

**File Crawling**:
- **Admin Path**: Crawler > File
- **Supports**: SMB, FTP, local file systems
- **Features**: Access control, file type filtering

**Data Store Crawling**:
- **Admin Path**: Crawler > Data Store
- **Supports**: Databases (via JDBC), CSV files, custom plugins
- **Features**: Incremental updates, custom field mapping

---

  virtual ImmediateExecutionContext* GetContext() const = 0;

  // Following two methods are used to support custom device.
  // Return true if the inputs contain custom device tensor handle. It means
  // that the argument need to be handled by a custom device.
  virtual bool HasCustomDeviceInput() const = 0;

  virtual const tensorflow::OpDef* OpDef() const = 0;

}{
	{ // 0 - Valid HTTP headers and valid metadata entries for bucket/object
		Headers: http.Header{
			"X-Amz-Server-Side-Encryption-Customer-Algorithm": []string{"AES256"},
			"X-Amz-Server-Side-Encryption-Customer-Key":       []string{"MzJieXRlc2xvbmdzZWNyZXRrZXltdXN0cHJvdmlkZWQ="},
			"X-Amz-Server-Side-Encryption-Customer-Key-Md5":   []string{"7PpPLAK26ONlVUGOWlusfg=="},
		},
		Bucket: "bucket",
		Object: "object",
		Metadata: map[string]string{

                                                 title="Floating point number" required="required"
                                                 data-validation="custom"
                                                 data-validation-regexp="(\+|\-)?\d+(\.\d+)?((e|E)(\+|\-)?\d+)?"
                                                 data-validation-help="number (Float)"/>

                .put("analysis.analyzer.test_reading_term_analyzer.tokenizer", "standard")
                .put("analysis.analyzer.test_reading_analyzer_ja.type", "custom")
                .put("analysis.analyzer.test_reading_analyzer_ja.tokenizer", "keyword")
                .put("analysis.analyzer.test_reading_term_analyzer_ja.type", "custom")

   * OkHttp in the current runtime. Use this to include the OkHttp version in custom `User-Agent`
   * headers.
   *
   * Official OkHttp releases follow [semantic versioning][semver]. Versions with the `-SNAPSHOT`
   * qualifier are not unique and should only be used in development environments. If you create
   * custom builds of OkHttp please include a qualifier your version name, like "4.7.0-mycompany.3".

            }
        };

        assertEquals("Custom protocolType should be WEB", ProtocolType.WEB, customAnnotation.protocolType());
        assertEquals("Custom message should match", "Test message", customAnnotation.message());
        assertEquals("Custom groups should have one element", 1, customAnnotation.groups().length);
        assertEquals("Custom payload should have one element", 1, customAnnotation.payload().length);