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5.3.6 Custom result handlers

Introduction​

Implement ResultHandler to customize result formats, HTTP status and response headers.

Purpose​

The handler receives ResultContext with the value, success flag, result code, message, error location, timing, exception and resolved options, then returns ResultInfo.

If the handler throws or returns null, Dataway produces a Structure failure response without calling the handler again.

APIPurpose
ResultInfoUtils.json(status, data)Set status and write JSON
ResultInfoUtils.toResult(binaryModel)Send binary content, including upload filename and content type
ResultInfoUtils.binary(contentType, bytes)Send bytes with a content type
ResultInfoUtils.stream(contentType, stream)Send and close an input stream
response.setStatus(status)Set HTTP status, default 200
response.getHeaders().put(name, value)Set response headers

Usage​

This handler reads HTTP status from its resolved options, returns JSON with X-Result: created on success, and delegates failures to Structure:

CreatedResultHandler.java
package example;

import net.hasor.dataway.model.ResultInfo;
import net.hasor.dataway.service.ResultInfoUtils;
import java.util.Map;
import net.hasor.dataway.result.AbstractResultHandler;
import net.hasor.dataway.result.ResultContext;
import net.hasor.dataway.result.structure.StructureResultHandler;

public class CreatedResultHandler extends AbstractResultHandler {
    public CreatedResultHandler(Map<String, ?> defaults) {
        super(defaults);
    }

    @Override
    public ResultInfo handle(ResultContext context) {
        if (!context.isSuccess()) {
            return new StructureResultHandler().handle(context);
        }
        int status = ((Number) context.getOptions().get("status")).intValue();
        ResultInfo response = ResultInfoUtils.json(status, context.getValue());
        response.getHeaders().put("X-Result", "created");
        return response;
    }
}

Configuration​

Register the handler as created in the application's DatawayConfig:

Register the result handler
Map<String, Object> defaults = Map.of("status", 201);
config.resultHandler("created", new CreatedResultHandler(defaults));

Select created in the API's resultHandler option to send its execution results to CreatedResultHandler:

API options
{"resultHandler": "created", "status": 202}

The handler appears in the console dropdown. The API overrides the constructor's status 201 with 202. Registering the same name replaces the handler; default is reserved.

AbstractResultHandler merges and isolates options. To validate them, override prepareOptions and check the map returned by super.prepareOptions(options).