java - REST API 请求
问题描述
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.io.StringReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.population.population.estimator.model.Country;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
public class PopulationService {
public void getPopulation() {
String query_url = "https://data.opendatasoft.com/api/records/1.0/search/?dataset=world-population%40kapsarc&facet=country_name&facet=year&refine.country_name=Australia&refine.year=2000";
try {
URL url = new URL(query_url);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(25000);
conn.setRequestProperty("content-type","application/json; charset=utf-8");
conn.setDoOutput(true);
conn.setDoInput(true);
conn.setRequestMethod("GET");
conn.connect();
OutputStream out = conn.getOutputStream();
int status = conn.getResponseCode();
} catch (Exception e) {
System.out.println(e);
}
}
public static void main(String args[]) {
getPopulation();
}
}
以下是显示异常详细信息的输出。
java.io.IOException：服务器返回 HTTP 响应代码：400 用于 URL： https ://data.opendatasoft.com/api/records/1.0/search/?dataset=world-population%40kapsarc&facet=country_name&facet=year&refine.country_name=Australia&refine .年=2000
堆栈跟踪：
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at sun.net.www.protocol.http.HttpURLConnection$10.run(HttpURLConnection.java:1890)
at sun.net.www.protocol.http.HttpURLConnection$10.run(HttpURLConnection.java:1885)
at java.security.AccessController.doPrivileged(Native Method)
at sun.net.www.protocol.http.HttpURLConnection.getChainedException(HttpURLConnection.java:1884)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1457)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1441)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:254)
at org.population.population.estimator.service.PopulationService.getPopulation(PopulationService.java:55)
at org.population.population.estimator.resources.PopulationResource.getPopulation(PopulationResource.java:20)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:143)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:160)
at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$TypeOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:203)
at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:97)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:389)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:347)
at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:102)
at org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:303)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:286)
at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1072)
at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:399)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:381)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:344)
at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:221)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:526)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:861)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1579)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.IOException: Server returned HTTP response code: 400 for URL: https://data.opendatasoft.com/api/records/1.0/search/?dataset=world-population%40kapsarc&facet=country_name&facet=year&refine.country_name=Australia&refine.year=2000
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1840)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1441)
at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:480)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getResponseCode(HttpsURLConnectionImpl.java:338)
at org.population.population.estimator.service.PopulationService.getPopulation(PopulationService.java:52)
... 48 more
只是将查询放在浏览器中会返回响应，但通过我的程序，我得到一个错误。如果有人可以帮助我将不胜感激。
我正在创建休息服务
解决方案
首先，您必须使用 InputStream，因为您正在从响应中读取数据。其次，您必须接受您必须使用的 json 响应conn.setRequestProperty("Accept", "application/json");
我修改了你的程序，请检查。
public class PopulationService {
public static void getPopulation() {
String query_url =
"https://data.opendatasoft.com/api/records/1.0/search/?dataset=world-population@kapsarc&facet=country_name&facet=year&refine.country_name=Australia&refine.year=2000";
try {
URL url = new URL(query_url);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestProperty("Accept", "application/json");
conn.setDoOutput(true);
conn.setRequestMethod("GET");
conn.connect();
BufferedReader br = new BufferedReader(new InputStreamReader(
(conn.getInputStream())));
String output;
System.out.println("Response Server .... \n");
while ((output = br.readLine()) != null) {
System.out.println(output);
}
conn.disconnect();
int status = conn.getResponseCode();
System.out.println("Status Code: "+status);
} catch (Exception e) {
System.out.println(e);
}
}
public static void main(String args[]) {
getPopulation();
}
}
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