When building GET API requests, query parameter values may contain special characters such as spaces, &, =, ?, (, ), *, %, and others.

These characters have specific meanings in URLs and can lead to incorrect request parsing if not properly encoded.

URL encoding ensures that special characters are safely transmitted and correctly interpreted by the API.

GET /intelligence/api/knowledge-models/km_id/data?filterExpr=status eq 'active' and department eq 'Sales & Marketing' and name eq 'John'

This fails because & acts as a parameter separator and spaces must be URL-encoded.

GET /intelligence/api/knowledge-models/km_id/data?filterExpr=status%20eq%20%27active%27%20and%20department%20eq%20%27Sales%20%26%20Marketing%27%20and%20name%20eq%20%27John%27

Here, the filterExpr value is URL-encoded:

• Spaces → %20
• & (ampersand) → %26
• ' (single quote) → %27

Without encoding, & would be interpreted as a separator between query parameters, breaking the request. Encoding ensures that all characters are correctly interpreted as part of the filter expression.

Use built-in URL encoding functions to ensure correct formatting of query parameter values.

Most programming languages provide built-in functions for URL encoding. The following examples show how to encode a string value before adding it to a request URL.

Use encodeURIComponent().

const filter = "name eq 'Sales & Marketing'";
const encodedFilter = encodeURIComponent(filter);

// Encoded result:
// name%20eq%20%27Sales%20%26%20Marketing%27

Use urllib.parse.quote().

from urllib.parse import quote

filter = "name eq 'Sales & Marketing'"
encoded_filter = quote(filter)

// Encoded result:
// name%20eq%20%27Sales%20%26%20Marketing%27

Use URLEncoder.encode().

import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;

String filter = "name eq 'Sales & Marketing'";
String encodedFilter = URLEncoder.encode(filter, StandardCharsets.UTF_8);

// Encoded result:
// name+eq+%27Sales+%26+Marketing%27

Use HttpUtility.UrlEncode() from System.Web or WebUtility.UrlEncode() from System.Net.

using System.Net;

string filter = "name eq 'Sales & Marketing'";
string encodedFilter = WebUtility.UrlEncode(filter);

// Encoded result:
// name+eq+%27Sales+%26+Marketing%27

For quick tests, you can also use online URL encoder/decoder tools.

If you are using an OpenAPI-generated client, query parameter encoding is typically handled automatically by the generated code or the underlying HTTP library.

In this case, you can pass the raw filter expression as a parameter filter, without manually encoding it.

filterExpr: "name eq 'Sales & Marketing'"

See available generators: https://openapi-generator.tech/docs/generators/