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Java REST Client to consume any REST API
// File: RestClient.java
package com.example;
import org.apache.http.HttpEntity;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.*;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.json.simple.JSONObject;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
// Maven dependancy
/*
<dependency>
<groupId>com.googlecode.json-simple</groupId>
<artifactId>json-simple</artifactId>
<version>1.1</version>
</dependency>
*/
public class RestClient {
private String endPoint;
private Map<String, String> headers = new HashMap<String, String>();
private String contentType;
public RestClient(String endPoint){
this.endPoint = endPoint;
}
public void setContentType(String contentType){
this.contentType = contentType;
headers.put("Content-Type", contentType);
}
public void setHeader(String key, String value){
headers.put(key, value);
}
public <T> Map<String, Object> sendPOSTRequest(T content) throws IOException {
String responseStr;
String bodyContent;
if(headers != null){
String contentType = headers.get("Content-Type");
if(contentType != null) this.setContentType(contentType);
}
HttpPost postRequest = new HttpPost(endPoint);
if(contentType != null && contentType.equalsIgnoreCase("application/json")){
bodyContent = ((JSONObject) content).toJSONString();
}else{
bodyContent = (String) content;
}
postRequest.setEntity(new StringEntity(bodyContent));
Map<String, Object> responseMap = sendRequest(postRequest);
return responseMap;
}
public <T> Map<String, Object> sendPUTRequest(T content) throws IOException {
String responseStr;
String bodyContent;
if(headers != null){
String contentType = headers.get("Content-Type");
if(contentType != null) this.setContentType(contentType);
}
HttpPut putRequest = new HttpPut(endPoint);
if(contentType != null && contentType.equalsIgnoreCase("application/json")){
bodyContent = ((JSONObject) content).toJSONString();
}else{
bodyContent = (String) content;
}
putRequest.setEntity(new StringEntity(bodyContent));
Map<String, Object> responseMap = sendRequest(putRequest);
return responseMap;
}
public Map<String, Object> sendGETRequest() throws IOException {
if(headers != null){
String contentType = headers.get("Content-Type");
if(contentType != null) this.setContentType(contentType);
}
HttpGet getRequest = new HttpGet(endPoint);
Map<String, Object> responseMap = sendRequest(getRequest);
return responseMap;
}
private Map<String, Object> sendRequest(HttpRequestBase request) throws IOException {
Map<String, Object> responseMap = new HashMap<String, Object>();
if(contentType != null) request.addHeader("Content-Type", contentType);
if(headers != null){
for(String key : headers.keySet()){
if(key.equalsIgnoreCase("Content-Type")) continue;
request.addHeader(key, (String) headers.get(key));
}
}
request.setConfig(getRequestConfig());
try (CloseableHttpClient closeableHttpClient = HttpClients.createDefault();
CloseableHttpResponse closeableHttpResponse = closeableHttpClient.execute(request)) {
HttpEntity httpResponseEntity = closeableHttpResponse.getEntity();
responseMap.put("StatusCode", closeableHttpResponse.getStatusLine().getStatusCode());
responseMap.put("ResponseBody", EntityUtils.toString(httpResponseEntity));
} catch (IOException e) {
e.printStackTrace();
throw new RuntimeException(e);
}
return responseMap;
}
private RequestConfig getRequestConfig(){
RequestConfig.Builder requestConfig = RequestConfig.custom();
requestConfig.setConnectTimeout(15 * 1000);
requestConfig.setConnectionRequestTimeout(15 * 1000);
requestConfig.setSocketTimeout(15 * 1000);
return requestConfig.build();
}
}
// Example call
/*
try{
RestClient restClient = new RestClient("https://reqres.in/api/unknown/2");
Map<String, Object> response = restClient.sendGETRequest();
}catch (Exception e){
e.getStackTrace();
}
*/
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