Converting between JSON and XML for FHIR.

com.ainq.kboone.tools.Converter.java

package com.ainq.kboone.tools;

import java.io.File;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.List;
import org.apache.commons.io.FileUtils;
import org.hl7.fhir.instance.model.api.IBaseResource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.DefaultApplicationArguments;
import ca.uhn.fhir.context.FhirContext;
import ca.uhn.fhir.parser.IParser;

/**
 * Convert a file from JSON to XML or XML to JSON
 * using various FHIR Versions.
 *
 * To use this, you need
 *      <dependency>
 *          <groupId>ca.uhn.hapi.fhir</groupId>
 *          <artifactId>hapi-fhir-structures-hl7org-dstu2</artifactId>
 *          <version>4.2.0</version>
 *      </dependency>
 *      <dependency>
 *          <groupId>ca.uhn.hapi.fhir</groupId>
 *          <artifactId>hapi-fhir-structures-r4</artifactId>
 *          <version>4.2.0</version>
 *      </dependency>
 *      <dependency>
 *          <groupId>ca.uhn.hapi.fhir</groupId>
 *          <artifactId>hapi-fhir-validation-resources-dstu2</artifactId>
 *          <version>4.2.0</version>
 *      </dependency>
 *      <dependency>
 *          <groupId>org.springframework.boot</groupId>
 *          <artifactId>spring-boot-starter-actuator</artifactId>
 *          <version>1.5.6.RELEASE</version>
 *      </dependency>
 *
 * @author Keith W. Boone
 *
 */

public class Converter  {
    public static final Logger LOGGER = LoggerFactory.getLogger(Converter.class);

    private static <T> T coalesce(T a, T b) {
        return a != null ? a : b;
    }

    public static void main(String args[]) {
        ApplicationArguments cmdLineArgs = new DefaultApplicationArguments(args);
        FhirContext ctx = null;
        String version = "default";
        if (cmdLineArgs.containsOption("v") || cmdLineArgs.containsOption("version")) {
            List<String> versions = coalesce(cmdLineArgs.getOptionValues("v"), cmdLineArgs.getOptionValues("version"));
            if (!versions.isEmpty()) {
                if (versions.size() > 1) {
                    LOGGER.error("Can only convert one version at a time: {}", versions);
                    System.exit(1);
                }
                version = versions.get(0);
            }
        }
        switch (version.toLowerCase()) {
        case "dstu2":
            ctx = FhirContext.forDstu2Hl7Org();
            break;
        case "stu3":
            ctx = FhirContext.forDstu3();
            break;
        case "default":
        case "r4":
            ctx = FhirContext.forR4();
            break;
        }
        for (String arg: cmdLineArgs.getNonOptionArgs()) {
            convert(ctx, arg);
        }
    }

    private static void convert(FhirContext ctx, String arg) {
        IParser jp = ctx.newJsonParser(),
                xp = ctx.newXmlParser();
        String input = null, output = null, file = null;
        try {
            input = FileUtils.readFileToString(new File(arg), StandardCharsets.UTF_8);
        } catch (IOException e) {
            LOGGER.error("Error reading {}", arg, e);
                return;
            }

            boolean inputIsXml = false;
            if (arg.toLowerCase().endsWith(".xml")) {
                inputIsXml = true;
            }

            IParser ip = inputIsXml ? xp : jp,
                    op = inputIsXml ? jp : xp;
            IBaseResource ri = null;
            ri = ip.parseResource(input);
            output = op.setPrettyPrint(true).encodeResourceToString(ri);
            try {
                file = arg.replace(inputIsXml ? "xml" : "json",
                inputIsXml ? "json" : "xml");
            FileUtils.writeStringToFile(new File(file), output, StandardCharsets.UTF_8);
        } catch (IOException e) {
            LOGGER.error("Error reading {}", arg, e);
            return;
        }
        LOGGER.info("Converted {} to {}", arg, file);
    }
}

This is a simple program to Convert between JSON and XML representations for FHIR Resources.

Usage: java com.ainq.kboone.tools.Converter resourceFileName{.json|.xml} ...