[英]How to call multiple rest api parallel in Java?
在 Java 中并行调用多个 api 的最佳方法是什么? 我想做多个rest调用,组合结果并返回一个jsonArray。 我正在使用 ExecutorService 并在我仅从一台客户端 PC 访问 url 时获得正确的输出。 但是当我从多个客户端访问 url 时,即使我调用相同的 url,每次我也会得到一个不同大小的 jsonArray。
我所做的如下:
ExecutorService executor = Executors.newFixedThreadPool(5);
resultArray = new JSONArray();
for (Branch branch : Branches) {
Future<Response> response = executor.submit(new Request(branch.getUrl(),
branch.getUserName(), branch.getPassword()));
responseBody = response.get().getResponseBody();
resultArray.put(responseBody);
}
executor.shutdown();
while(!executor.isTerminated()) {
}
return resultArray.toString();
public class Request implements Callable<Response> {
private HttpURLConnection con;
private URL obj;
private String response;
private String url;
private String username;
private String password;
public Request(String url, String username, String password) {
this.url = url;
this.username = username;
this.password = password;
}
@Override
public Response call() {
try {
obj = new URL(url);
con = (HttpURLConnection) obj.openConnection();
String userCredentials = username + ":" + password;
String basicAuth = "Basic " + java.util.Base64.getEncoder().encodeToString(userCredentials.getBytes());
con.setRequestProperty ("Authorization", basicAuth);
con.setRequestMethod("GET");
int responseCode = con.getResponseCode();
if(responseCode == 200) {
BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer stringBuffer = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
stringBuffer.append(inputLine);
}
in.close();
response = stringBuffer.toString();
return new Response(responseCode, response);
}
else {
response = "{\"response\":\"some error occurred\"}";
return new Response(responseCode, response);
}
} catch (IOException e) {
response = "{\"output\":\"some error occurred\"}";
return new Response(404, response);
}
}
}
public class Response {
private String responseBody;
private int responseCode;
public Response(int responseCode, String responseBody) {
this.responseBody = responseBody;
this.responseCode = responseCode;
}
public int getResponseCode() {
return responseCode;
}
public String getResponseBody() {
return responseBody;
}
}
请检查这个,
Collection<Callable<Response>> tasks = new ArrayList<>();
for (Branch branch : Branches) {
tasks.add(new Request(branch.getUrl(), branch.getUserName(), branch.getPassword()));
}
int numThreads = Branches.size() > 4 ? 4 : Branches.size();
ExecutorService executor = Executors.newFixedThreadPool(numThreads);
List<Future<Response>> results = executor.invokeAll(tasks);
for(Future<Response> response : results){
responseBody = response.get().getResponseBody();
resultArray.put(responseBody);
}
从 Java 7 开始,我们可以尝试用 ForkJoin Pool 替换 ExecutorService,
Collection<Callable<Response>> tasks = new ArrayList<>();
for (Branch branch : Branches) {
tasks.add(new Request(branch.getUrl(), branch.getUserName(), branch.getPassword()));
}
int numThreads = Branches.size() > 4 ? 4 : Branches.size();
ForkJoinPool pool = new ForkJoinPool(Runtime.getRuntime().availableProcessors());
List<Future<Response>> results = pool.invokeAll(tasks);
for(Future<Response> response : results){
responseBody = response.get().getResponseBody();
resultArray.put(responseBody);
}
注意:- 代码未经测试,几个月前我使用过类似的东西。
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