Rest Client HTTP (HttpURLConnection)

Samples | Rest Client HTTP (HttpURLConnection)

Notes
Maven dependencies
GET Method
POST Method (url parameters)
POST Method (form parameters)

Notes
See this page for an example of a REST application: JAX-RS: Sample Application (Jersey, Spring, Tomcat)

Maven dependencies

<dependency>
    <groupId>javax.ws.rs</groupId>
    <artifactId>javax.ws.rs-api</artifactId>
    <version>2.1.1</version>
</dependency>

GET Method

Java example:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.List;
import java.util.Map;

import javax.ws.rs.HttpMethod;
import javax.ws.rs.core.MediaType;

public class Test {
    public static void main(String[] args) throws IOException {
        final String urlString = "http://localhost:8080/mtitek-rest-sample-1.0.0-SNAPSHOT/rest/myEntity/getMyEntity1?qpvalue1=val11&qpvalue2=val21&qpvalue3=val31";

        final int connectTimeout = 1000;

        HttpURLConnection connection = null;

        try {
            final URL url = new URL(urlString);

            connection = (HttpURLConnection) url.openConnection();

            connection.setConnectTimeout(connectTimeout);

            connection.setRequestMethod(HttpMethod.GET);

            connection.setRequestProperty("Accept", MediaType.APPLICATION_XML);

            // response code
            System.out.println(connection.getResponseCode());

            // response headers
            final Map<String, List<String>> headerFields = connection.getHeaderFields();
            for (Map.Entry<String, List<String>> entry : headerFields.entrySet()) {
                System.out.println("Header [Key: " + entry.getKey() + " - Value: " + entry.getValue() + "]");
            }

            // response body
            if (connection.getInputStream() != null) {
                final InputStream inputStream = connection.getInputStream();
                final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

                try {
                    final StringBuilder response = new StringBuilder();

                    String line;
                    while ((line = bufferedReader.readLine()) != null) {
                        response.append(line);
                    }

                    System.out.println(response.toString());
                } finally {
                    if (bufferedReader != null) {
                        bufferedReader.close();
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
    }
}

Sample JAX-RS GET resource:

@GET
@Path("/getMyEntity1")
public Response getMyEntity1(@QueryParam(value = "qpvalue1") final String value1,
        @QueryParam(value = "qpvalue2") final String value2,
        @QueryParam(value = "qpvalue3") final String value3) {
    MyEntity myEntity = new MyEntity();

    //...

    return Response.ok(myEntity).build();
}

Request/Response:

200
Header [Key: null - Value: [HTTP/1.1 200]]
Header [Key: Content-Length - Value: [688]]
Header [Key: Date - Value: [Mon, 21 Oct 2018 00:45:54 GMT]]
Header [Key: Content-Type - Value: [application/xml]]
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><myEntity ...

POST Method (url parameters)

Java example:

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.List;
import java.util.Map;

import javax.ws.rs.HttpMethod;
import javax.ws.rs.core.MediaType;

public class Test {
    public static void main(String[] args) throws IOException {
        final String urlString = "http://localhost:8080/mtitek-rest-sample-1.0.0-SNAPSHOT/rest/myEntity/postMyEntity1?qpvalue1=val11&qpvalue2=val21&qpvalue3=val31";

        final int connectTimeout = 1000;

        HttpURLConnection connection = null;

        try {
            final URL url = new URL(urlString);

            connection = (HttpURLConnection) url.openConnection();

            connection.setConnectTimeout(connectTimeout);

            connection.setRequestMethod(HttpMethod.POST);

            connection.setRequestProperty("Content-Type", MediaType.APPLICATION_FORM_URLENCODED);
            connection.setRequestProperty("Accept", MediaType.APPLICATION_XML);

            connection.setUseCaches(false);
            connection.setDoOutput(true);

            final OutputStream outputStream = connection.getOutputStream();

            final DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
            dataOutputStream.close();

            // response code
            System.out.println(connection.getResponseCode());

            // response headers
            final Map<String, List<String>> headerFields = connection.getHeaderFields();
            for (Map.Entry<String, List<String>> entry : headerFields.entrySet()) {
                System.out.println("Header [Key: " + entry.getKey() + " - Value: " + entry.getValue() + "]");
            }

            // response body
            if (connection.getInputStream() != null) {
                final InputStream inputStream = connection.getInputStream();

                final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

                try {
                    StringBuilder response = new StringBuilder();

                    String line;
                    while ((line = bufferedReader.readLine()) != null) {
                        response.append(line);
                    }

                    System.out.println(response.toString());
                } finally {
                    if (bufferedReader != null) {
                        bufferedReader.close();
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
    }
}

Sample JAX-RS POST resource:

@POST
@Path("/postMyEntity1")
public Response postMyEntity1(@QueryParam(value = "qpvalue1") final String value1,
        @QueryParam(value = "qpvalue2") final String value2,
        @QueryParam(value = "qpvalue3") final String value3) {
    MyEntity myEntity = new MyEntity();

    //...

    return Response.ok(myEntity).build();
}

Request/Response:

200
Header [Key: null - Value: [HTTP/1.1 200]]
Header [Key: Content-Length - Value: [996]]
Header [Key: Date - Value: [Mon, 21 Oct 2018 00:48:39 GMT]]
Header [Key: Content-Type - Value: [application/xml]]
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><myEntity ...

POST Method (form parameters)

Java example:

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.List;
import java.util.Map;

import javax.ws.rs.HttpMethod;
import javax.ws.rs.core.MediaType;

public class Test {
    public static void main(String[] args) throws IOException {
        final String urlString = "http://localhost:8080/mtitek-rest-sample-1.0.0-SNAPSHOT/rest/myEntity/postMyEntity2";
        final String formParameters = "qpvalue1=val11&qpvalue2=val21&qpvalue3=val31";

        final int connectTimeout = 1000;

        HttpURLConnection connection = null;

        try {
            final URL url = new URL(urlString);

            connection = (HttpURLConnection) url.openConnection();

            connection.setConnectTimeout(connectTimeout);

            connection.setRequestMethod(HttpMethod.POST);

            connection.setRequestProperty("Content-Type", MediaType.APPLICATION_FORM_URLENCODED);
            connection.setRequestProperty("Accept", MediaType.APPLICATION_XML);

            connection.setUseCaches(false);
            connection.setDoOutput(true);

            final OutputStream outputStream = connection.getOutputStream();

            final DataOutputStream dataOutputStream = new DataOutputStream(outputStream);
            dataOutputStream.writeBytes(formParameters);
            dataOutputStream.close();

            // response code
            System.out.println(connection.getResponseCode());

            // response headers
            final Map<String, List<String>> headerFields = connection.getHeaderFields();
            for (Map.Entry<String, List<String>> entry : headerFields.entrySet()) {
                System.out.println("Header [Key: " + entry.getKey() + " - Value: " + entry.getValue() + "]");
            }

            // response body
            if (connection.getInputStream() != null) {
                final InputStream inputStream = connection.getInputStream();

                final BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

                try {
                    StringBuilder response = new StringBuilder();

                    String line;
                    while ((line = bufferedReader.readLine()) != null) {
                        response.append(line);
                    }

                    System.out.println(response.toString());
                } finally {
                    if (bufferedReader != null) {
                        bufferedReader.close();
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
        }
    }
}

Sample JAX-RS POST resource:

@POST
@Path("/postMyEntity2")
@Consumes({ MediaType.APPLICATION_FORM_URLENCODED })
public Response postMyEntity2(@FormParam(value = "qpvalue1") final String value1,
        @FormParam(value = "qpvalue2") final String value2,
        @FormParam(value = "qpvalue3") final String value3) {
    MyEntity myEntity = new MyEntity();

    //...

    return Response.ok(myEntity).build();
}

Request/Response:

200
Header [Key: null - Value: [HTTP/1.1 200]]
Header [Key: Content-Length - Value: [934]]
Header [Key: Date - Value: [Mon, 21 Oct 2018 00:49:58 GMT]]
Header [Key: Content-Type - Value: [application/xml]]
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><myEntity ...