How to Verify US Addresses in Java / Spring Boot

What the API returns

Every response is wrapped in a standard envelope. For verification, the Result field is a single object describing the matched address. This is a real response for 1600 Pennsylvania Ave NW:

{
  "Id": "118a23c7-d836-46af-a17f-022a3754e36c",
  "Result": {
    "inputAddress": "1600 Pennsylvania Ave NW Washington DC 20500",
    "fullAddress": "1600 Pennsylvania Ave NW, Washington, DC 20500-0005",
    "addressLine1": "1600 Pennsylvania Ave NW",
    "addressLine2": "Washington, DC 20500-0005",
    "unitType": null,
    "unitNumber": null,
    "city": "Washington",
    "stateCode": "DC",
    "county": "District Of Columbia",
    "zipCode": "20500",
    "zip4": "0005",
    "dpvConfirmation": "Y",
    "deliverableStatus": "Confirmed",
    "confidence": 0.6,
    "matchTier": "Approximate",
    "matchMode": "Speculative",
    "matchCode": {
      "houseNumber": "Matched",
      "street": "Matched",
      "unit": "NotApplicable",
      "city": "Matched",
      "state": "Matched",
      "zipCode": "Matched",
      "zip4": "Inferred"
    },
    "lastVerifiedDate": "2026-06-16T22:40:51",
    "footnotes": ["recovered: standardized via correction, not an exact match"]
  },
  "ClientSessionId": null,
  "StatusCode": 200,
  "IsError": false,
  "Errors": []
}

The fields you'll use most often:

• fullAddress - the postal-standardized address. Store this, not the user's raw input.
• deliverableStatus - a plain-English summary of deliverability (covered below). Branch your checkout on this.
• unitType / unitNumber - the confirmed apartment or suite as discrete fields (e.g. APT, 4B), or null when there is no unit. Only a postal-confirmed unit appears here.
• zip4 and county - appended for you even when the input only had a 5-digit ZIP.
• matchTier and confidence - how the match was reached. The example above is Approximate / 0.6 because speculative mode standardized the input rather than matching it verbatim - still Confirmed as deliverable.
• matchCode - a per-component breakdown (Matched / Corrected / Inferred / Unmatched / NotApplicable) so you can see exactly which fields were trusted versus fixed. (The response also carries postal routing fields - carrierRoute, deliveryPoint, elot - omitted above for brevity.)

Get your API key

1. Sign up at sthan.io and subscribe to the free Address Verification tier
2. Open your dashboard and create an API key
3. Copy the key - it looks like sthan_live_xxxxxxxxxxxxxxxx

You get the key immediately, with no approval queue. An API key is the simplest way to authenticate: you send it as a Bearer token on every request and there is no separate login step. (If you prefer a short-lived token, there is a JWT flow covered later.)

Configure the project

Java 11+ ships with java.net.http.HttpClient, so the only dependency you add is Jackson for JSON. With Maven:

<dependency>
  <groupId>com.fasterxml.jackson.core</groupId>
  <artifactId>jackson-databind</artifactId>
  <version>2.17.0</version>
</dependency>

Keep your key out of source control by reading it from the environment:

# Set the key in your shell or your run configuration
export STHAN_API_KEY="sthan_live_xxxxxxxxxxxxxxxx"

Build the verification client

First, model the response with two records. The envelope keys are PascalCase, so map them with @JsonProperty; the inner fields are camelCase and map by name:

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.annotation.JsonProperty;
import java.util.List;

@JsonIgnoreProperties(ignoreUnknown = true)
record SthanResponse(
        @JsonProperty("Result") VerifiedAddress result,
        @JsonProperty("IsError") boolean isError,
        @JsonProperty("Errors") List<String> errors) {
}

@JsonIgnoreProperties(ignoreUnknown = true)
record VerifiedAddress(
        String fullAddress,
        String addressLine1,
        String addressLine2,
        String unitType,
        String unitNumber,
        String city,
        String stateCode,
        String county,
        String zipCode,
        String zip4,
        String dpvConfirmation,
        String deliverableStatus,
        double confidence,
        String matchTier,
        String matchMode) {
}

Now the client itself. It takes a shared HttpClient and ObjectMapper, URL-encodes the address, calls the endpoint, unwraps the envelope, and returns the Result:

import com.fasterxml.jackson.databind.ObjectMapper;
import java.net.URI;
import java.net.URLEncoder;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.nio.charset.StandardCharsets;

class VerificationException extends RuntimeException {
    VerificationException(String message) {
        super(message);
    }
}

public class VerificationClient {
    private static final String BASE_URL = "https://api.sthan.io";

    private final HttpClient http = HttpClient.newHttpClient();
    private final ObjectMapper mapper = new ObjectMapper();
    private final String apiKey;

    public VerificationClient(String apiKey) {
        this.apiKey = apiKey;
    }

    public VerifiedAddress verify(String address, String mode) throws Exception {
        // URLEncoder targets query strings, so swap '+' back to %20 for the path
        String encoded = URLEncoder.encode(address.strip(), StandardCharsets.UTF_8)
                .replace("+", "%20");
        URI uri = URI.create(BASE_URL + "/v2/address-verification/usa/"
                + encoded + "?match=" + mode);

        HttpRequest request = HttpRequest.newBuilder(uri)
                .header("Authorization", "Bearer " + apiKey)
                .GET()
                .build();

        HttpResponse<String> response =
                http.send(request, HttpResponse.BodyHandlers.ofString());
        if (response.statusCode() >= 400) {
            throw new VerificationException("HTTP " + response.statusCode());
        }

        SthanResponse envelope = mapper.readValue(response.body(), SthanResponse.class);
        if (envelope.isError()) {
            throw new VerificationException(String.join(", ", envelope.errors()));
        }
        return envelope.result();
    }
}

That's the whole integration. One call:

var client = new VerificationClient(System.getenv("STHAN_API_KEY"));
VerifiedAddress result =
        client.verify("1600 pennsylvania ave nw washington dc 20500", "speculative");

System.out.println(result.fullAddress());        // 1600 Pennsylvania Ave NW, Washington, DC 20500-0005
System.out.println(result.deliverableStatus());  // Confirmed
System.out.println(result.zip4());               // 0005

Choose a match mode

The match parameter controls how much typo tolerance the verifier applies. The same call supports four modes, from strictest to loosest:

If you omit match, the endpoint defaults to speculative for the widest recovery. Whichever mode you pick, the location-defining parts of the address - house number, ordinal, directional, state, and the street's core name - are never substituted. A looser mode only widens tolerance for misspellings of the same street, never a jump to a different one.

Interpret the result

deliverableStatus is the one field most integrations branch on. It collapses the raw postal DPV code into four plain values:

For richer logic, pair the status with matchCode. If matchCode.street() is Corrected, you know the verifier fixed a typo and should show the user the standardized address to confirm. If confidence is below your threshold or matchTier is Speculative, treat the result as a suggestion rather than a fact.

Verify at form submit

Verification belongs on the server, at the moment the user submits - not in the browser. The API does not enable CORS for browser requests, and your API key must never reach client-side JavaScript. Here is a Spring Boot controller that verifies the submitted address and returns a decision the front end can act on:

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;
import java.util.HashMap;
import java.util.Map;

@RestController
public class CheckoutController {

    private final VerificationClient client =
            new VerificationClient(System.getenv("STHAN_API_KEY"));

    @PostMapping("/checkout/address")
    public ResponseEntity<Map<String, Object>> submitAddress(
            @RequestBody Map<String, String> body) {
        String raw = body.getOrDefault("address", "").strip();
        if (raw.isEmpty()) {
            return ResponseEntity.badRequest()
                    .body(Map.of("ok", false, "reason", "empty"));
        }

        VerifiedAddress result;
        try {
            result = client.verify(raw, "speculative");
        } catch (Exception e) {
            // Don't punish the user for our hiccup: accept, but mark unverified.
            return ResponseEntity.ok(Map.of(
                    "ok", true, "verified", false, "standardized", raw));
        }

        String status = result.deliverableStatus();

        if ("NotDeliverable".equals(status)) {
            return ResponseEntity.unprocessableEntity().body(Map.of(
                    "ok", false,
                    "reason", "not_deliverable",
                    "message", "We couldn't confirm this address is deliverable. "
                            + "Please double-check it."));
        }

        String warning = null;
        if ("ConfirmedPrimaryOnly".equals(status)) {
            warning = "We confirmed the building but not the unit - check the apartment/suite.";
        } else if ("Unknown".equals(status)) {
            warning = "We couldn't fully confirm this address. Please make sure it's correct.";
        }

        Map<String, Object> out = new HashMap<>();
        out.put("ok", true);
        out.put("verified", "Confirmed".equals(status));
        out.put("standardized", result.fullAddress());
        out.put("warning", warning);
        return ResponseEntity.ok(out);
    }
}

The front end sends the raw address to /checkout/address and gets back a clean, standardized string plus a yes/warn/no decision. Store the standardized value - the postal-formatted fullAddress - rather than the user's original text, and you've turned a guess into shippable data.

Alternative: JWT authentication

An API key is the simplest option and is all most apps need. If your security policy prefers short-lived credentials, the platform also supports a 2-step JWT flow. You call GET /Auth/Token once with your profileName and profilePassword headers, receive a token valid for up to 60 minutes, then send that token as the Bearer value on subsequent calls:

@JsonIgnoreProperties(ignoreUnknown = true)
record TokenEnvelope(@JsonProperty("Result") Token result) {
}

@JsonIgnoreProperties(ignoreUnknown = true)
record Token(@JsonProperty("access_token") String accessToken) {
}

public String getToken() throws Exception {
    HttpRequest request = HttpRequest.newBuilder(URI.create(BASE_URL + "/Auth/Token"))
            .header("profileName", System.getenv("STHAN_PROFILE_NAME"))
            .header("profilePassword", System.getenv("STHAN_PROFILE_PASSWORD"))
            .GET()
            .build();

    HttpResponse<String> response =
            http.send(request, HttpResponse.BodyHandlers.ofString());
    TokenEnvelope envelope = mapper.readValue(response.body(), TokenEnvelope.class);
    return envelope.result().accessToken();
}

You would then set the Authorization header to "Bearer " + token instead of the static key. Everything else - the endpoint, the envelope, the parsing - stays exactly the same. Cache the token and refresh it shortly before the 60-minute expiry rather than fetching one per request.

Handle errors

Two status codes are worth handling explicitly so a hiccup never blocks a sale:

• 401 - The key or token was rejected. Check the value and, on the JWT flow, refresh and retry once.
• 429 - Rate limit reached. Back off and retry, or accept the address unverified rather than failing the checkout.

public VerifiedAddress verifyWithRetry(String address, String mode, int retries)
        throws Exception {
    String encoded = URLEncoder.encode(address.strip(), StandardCharsets.UTF_8)
            .replace("+", "%20");
    URI uri = URI.create(BASE_URL + "/v2/address-verification/usa/"
            + encoded + "?match=" + mode);
    HttpRequest request = HttpRequest.newBuilder(uri)
            .header("Authorization", "Bearer " + apiKey)
            .GET()
            .build();

    for (int attempt = 0; ; attempt++) {
        HttpResponse<String> response =
                http.send(request, HttpResponse.BodyHandlers.ofString());
        if (response.statusCode() == 429 && attempt < retries) {
            Thread.sleep((long) Math.pow(2, attempt) * 1000); // 1s, then 2s
            continue;
        }
        if (response.statusCode() >= 400) {
            throw new VerificationException("HTTP " + response.statusCode());
        }
        return mapper.readValue(response.body(), SthanResponse.class).result();
    }
}

The exponential back-off (1s, then 2s) is enough for transient limits. For heavier batch jobs, add a circuit breaker so one bad minute doesn't stall the whole queue.

What's next: fix addresses before they're submitted

Verification confirms an address at submit. You can stop bad addresses even earlier by helping users enter the right one in the first place: Address Autocomplete suggests complete, postal-formatted addresses as the user types, so most submissions are already clean before verification runs. Autocomplete has its own free tier of 100,000 requests/month - pairing the two (autocomplete as they type, one verification call at submit) keeps both your data and your costs in good shape. The Java autocomplete walkthrough is here: Address Autocomplete in Java / Spring Boot.

If you need to break an address into components, parse freeform input, or get latitude/longitude, the same envelope and the same HttpClient pattern apply. The full Java walkthrough covering verification, parsing, and geocoding together is in Integrate Address APIs in Java.