quarkusio/quarkus · error · RuntimeException

Invalid proxy string. Expected

Error message

Invalid proxy string. Expected <hostname>:<port>, found '${proxy}'

What it means

ProxyAddressUtil.parseAddress splits a proxy string on the last ':' expecting the format <hostname>:<port>. This error is thrown when there is no colon (or the colon is the first/last character), so no valid host and port can be extracted. The library throws RuntimeException because the proxy address comes from user configuration and is unusable.

Solutions

1. Provide the proxy as host:port, e.g. proxy.corp.com:8080
2. Remove the trailing colon or add the missing port
3. Validate the string before assigning it to the config property

Example fix

# before
quarkus.rest-client.svc.proxy-address=proxy.corp.com
# after
quarkus.rest-client.svc.proxy-address=proxy.corp.com:8080

static boolean isValidProxyString(String s) {
    if (s == null) return false;
    int i = s.lastIndexOf(':');
    return i > 0 && i < s.length() - 1;
}

static boolean isHostPort(String s) {
    int i = s == null ? -1 : s.lastIndexOf(':');
    if (i <= 0 || i == s.length() - 1) return false;
    try { Integer.parseInt(s.substring(i + 1)); return true; } catch (NumberFormatException e) { return false; }
}

try {
    ProxyAddressUtil.parseAddress(proxy);
} catch (RuntimeException e) {
    throw new IllegalArgumentException("Proxy must be host:port, got: " + proxy, e);
}

When it happens

Trigger: Calling QuarkusRestClientBuilder.proxyAddress(String, int) alternatives / config properties (quarkus.rest-client.<name>.proxy-address-mapping or proxy-address) with a string lacking a colon, e.g. "localhost", ":8080", or "localhost:".

Common situations: Configured only the host without the port; copied a proxy URL including scheme (http://proxy:8080 handled differently) or trailing colon; env-based proxy value empty or malformed.

Related errors

• Invalid port number
• Invalid proxy setting. The port is not a number in
• proxyHost must not be null
• A REST Client Response object was returned from a server…
• A REST Client RestResponse object was returned from a…

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/8ad837e0feeaba41. Report an issue: GitHub.

Appendix: source

Thrown at extensions/resteasy-reactive/rest-client/runtime/src/main/java/io/quarkus/rest/client/reactive/runtime/ProxyAddressUtil.java:9

package io.quarkus.rest.client.reactive.runtime;

public class ProxyAddressUtil {

    public static HostAndPort parseAddress(String proxyString) {
        int lastColonIndex = proxyString.lastIndexOf(':');

        if (lastColonIndex <= 0 || lastColonIndex == proxyString.length() - 1) {
            throw new RuntimeException("Invalid proxy string. Expected <hostname>:<port>, found '" + proxyString + "'");
        }

        String host = proxyString.substring(0, lastColonIndex);
        int port;
        try {
            port = Integer.parseInt(proxyString.substring(lastColonIndex + 1));
        } catch (NumberFormatException e) {
            throw new RuntimeException("Invalid proxy setting. The port is not a number in '" + proxyString + "'", e);
        }
        return new HostAndPort(host, port);
    }

    @SuppressWarnings("ClassCanBeRecord") // don't convert to record because we have code that accesses the public field
    public static class HostAndPort {
        public final String host;
        public final int port;

        public HostAndPort(String host, int port) {

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