Invoking Rest API using java client passing json object

Question

I am new to JSON. I am invoking a public rest API https://api.gdc.cancer.gov/cases

I want to query all the cases for a particular disease type( for example TCGA-LAML mentioned below).

in SOAP Ui when I POST below request in JSON format .It gives me perfect answer { "filters": {"op":"in", "content":{ "field":"cases.project.project_id", "value":["TCGA-LAML"] } } }

But I have to call POST through a java client. Even after Trying hard I am not able to set the input parameters correctly.

I am posting my code here. Can you please help me correcting the code.

package downloadtoolproject; 
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import java.net.HttpURLConnection;
import java.net.URL;

public class Newtest {
    public static String sendPostRequest(String requestUrl, String payload) {
        StringBuffer jsonString = new StringBuffer();
        try {
            URL url = new URL(requestUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Accept", "application/json");
            connection.setRequestProperty("Content-Type", "application/json");
            OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
            writer.write(payload);
            writer.close();
            BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()));

            String line;
            while ((line = br.readLine()) != null)
            {
                jsonString.append(line);
                System.out.println(line);
            }
            br.close();
            connection.disconnect();
        }
        catch (Exception e) {
            throw new RuntimeException(e.getMessage());
        }
        return jsonString.toString() ;
    }

    public static void main(String [] args)
    {
        String payload = "{\"field\":\"project_id\",\"value\":[\"TCGA-LAML\"]}";
        String requestUrl="https://api.gdc.cancer.gov/cases";
        sendPostRequest(requestUrl, payload);
    }

}

Do you want to run this query :-> { "filters": {"op":"in", "content":{ "field":"cases.project.project_id", "value":["TCGA-LAML"] } } } ? — Bhavya Jain
– Bhavya Jain, Commented Jul 29, 2018 at 19:01
Yes Bhavya I want to run this query. But not able to make parameters of this. — user3151878
– user3151878, Commented Jul 29, 2018 at 19:02
Change "String payload" to -> String payload="{ \"filters\": {\"op\":\"in\", \"content\":{ \"field\":\"cases.project.project_id\", \"value\":[\"TCGA-LAML\"] } } }"; and now run your program and then tell me if you got your desired output, if yes then I will help you parameterise it! — Bhavya Jain
– Bhavya Jain, Commented Jul 29, 2018 at 19:04

Bhavya Jain · Accepted Answer · 2018-07-29 19:36:29Z

1

I think the following solution should work for you

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;

import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

public class Newtest {
    public static String sendPostRequest(String requestUrl, String payload) {
        StringBuffer jsonString = new StringBuffer();
        try {
            URL url = new URL(requestUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();

            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Accept", "application/json");
            connection.setRequestProperty("Content-Type", "application/json");
            OutputStreamWriter writer = new OutputStreamWriter(connection.getOutputStream());
            writer.write(payload);
            writer.close();
            BufferedReader br = new BufferedReader(new InputStreamReader(connection.getInputStream()));

            String line;
            while ((line = br.readLine()) != null) {
                jsonString.append(line);
                System.out.println(line);
            }
            br.close();
            connection.disconnect();
        } catch (Exception e) {
            throw new RuntimeException(e.getMessage());
        }
        return jsonString.toString();
    }

    public static void main(String[] args) {
        List<String> values = new ArrayList<>();
        values.add("TCGA-LAML");
        String requestUrl = "https://api.gdc.cancer.gov/cases";
        sendPostRequest(requestUrl, preparePayload(values));

    }

    private static String preparePayload(List<String> values) {
        StringBuilder sb = new StringBuilder();
        for (String value : values) {
            sb.append("\"" + value + "\",");
        }
        String desiredValue = sb.toString().substring(0, sb.toString().length() - 1);
        return "{ \"filters\": {\"op\":\"in\", \"content\":{ \"field\":\"cases.project.project_id\", \"value\":[" + desiredValue + "] } } }";
    }

}

You just need to add all the input values in the values List and pass it to the preparePayload method ,it will convert it into a valid payload.

edited Jul 29, 2018 at 19:36

answered Jul 29, 2018 at 19:30

Bhavya Jain

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5 Comments

Bhavya Jain Over a year ago

Its good to hear that. Please accept the answer and close this question. Thanks

user3151878 Over a year ago

Hi Bhavya. Really sorry for again troubling you. { "data": { "hits": [ { "updated_datetime": "2018-05-24T11:22:57.727521-05:00", "submitter_id": "TCGA-AB-2956", "id": "c1f908ce-f6d5-4", "disease_type": "Acute Myeloid Leukemia", } ] portion of response. I want to access submitter_id,id and disease_type in my java code. can you please help with that.

Bhavya Jain Over a year ago

stackoverflow.com/questions/28982412/… this will help you with json parsing

user3151878 Over a year ago

Thanks Bhavya I tried this. But it has some issues json-path 2.4.0 doesn't have the correct API. While in 3.0.0 I get ava.lang.NoClassDefFoundError: io/restassured/internal/assertion/AssertParameter

Bhavya Jain Over a year ago

Use the following pom entry to :-><dependency> <groupId>org.json</groupId> <artifactId>json</artifactId> <version>20160810</version> </dependency> . and remove the previous one, and I suggest you to start a new thread as answering your queries in comment section is difficult and not properly formatted

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