[英]How can I transfer an ArrayList<Map> via REST?
編輯:我試圖實現@Durgpal Singh和@Nikhil的建議。 我更改了代碼,因此看起來像這樣。
客戶:
Client client = ClientBuilder.newClient();
WebTarget target = client
.target("http://localhost:8087/api/ls3algorithm/" + petrinets + "/" + Integer.toString(k) + "/" + Float.toString(theta));
Invocation.Builder invocationBuilder = target.request(MediaType.APPLICATION_JSON);
Response response = invocationBuilder.get();
Map<String, List<Map>> result_ = response.readEntity(new GenericType<Map<String, List<Map>>>() { });
result = (ArrayList<Map>) result_.get("data");
服務器:
ArrayList<Map> result;
result = new Ls3Algorithm().execute(new File("petrinetze").getAbsolutePath(), k, theta);
Map<String, List<Map>> map = new HashMap<>();
map.put("data", result);
return Response.ok(map).build();
不幸的是,這導致Exception in thread "main" org.glassfish.jersey.message.internal.MessageBodyProviderNotFoundException: MessageBodyReader not found for media type=application/json, type=interface java.util.Map, genericType=java.util.Map<java.lang.String, java.util.List<java.util.Map>>.
我哪里出錯了?
我對RESTful Web服務還很陌生,目前正在編寫一個提供計算算法的微服務。 我正在測試以下發布的服務。
工作流程:客戶端將一些數據保存在MongoDB數據庫中,並通過@PathParam發送相關文件的名稱,作為GET請求的一部分。 然后,服務器從MongoDB中檢索文件,處理其算法,並將結果作為打包在Response
對象中的List<Map>
發送回去。
目標:將結果( List<Map>
)作為JSON傳輸並在客戶端控制台上打印出來。
客戶:
package ls3test;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Map;
import javax.ws.rs.client.Client;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.client.Invocation;
import javax.ws.rs.client.WebTarget;
import javax.ws.rs.core.GenericType;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.mongodb.DB;
import com.mongodb.MongoClient;
import com.mongodb.gridfs.GridFS;
import com.mongodb.gridfs.GridFSInputFile;
public class Ls3TransmissionTest {
final static String petrinets = "eins, zwei, drei, vier";
final static int k = 3;
final static float theta = 0.9f;
public static void main(String[] args) throws IOException {
[... save all the relevant files in the MongoDB ...]
ArrayList<Map> result = new ArrayList<Map>();
Client client = ClientBuilder.newClient();
WebTarget target = client
.target("http://localhost:8087/api/ls3algorithm/" + petrinets + "/" + Integer.toString(k) + "/" + Float.toString(theta));
Invocation.Builder invocationBuilder = target.request(MediaType.APPLICATION_JSON);
Response response = invocationBuilder.get();
result = response.readEntity(new GenericType<ArrayList<Map>>() {
});
ObjectWriter ow = new ObjectMapper().writer().withDefaultPrettyPrinter();
String json = ow.writeValueAsString(result);
}
}
服務器:
package service;
import com.fasterxml.jackson.core.JsonGenerationException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.mongodb.DB;
import com.mongodb.MongoClient;
import com.mongodb.gridfs.GridFS;
import com.mongodb.gridfs.GridFSDBFile;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.GenericEntity;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.util.List;
import java.util.Map;
@SuppressWarnings("deprecation")
@Path("/ls3algorithm")
public class Resource {
// SLF4J is provided with Dropwizard
Logger log = LoggerFactory.getLogger(Resource.class);
@SuppressWarnings("rawtypes")
@GET
@Path("/{petrinets}/{k}/{theta}")
@Produces(MediaType.APPLICATION_JSON)
public Response ls3execute(@PathParam("petrinets") String petrinetNames, @PathParam("k") int k,
@PathParam("theta") float theta) {
[... get all the relevant files from the MongoDB ...]
List<Map> result;
Ls3Algorithm ls3Algorithm = new Ls3Algorithm();
result = ls3Algorithm.execute(new File("petrinetze").getAbsolutePath(), k, theta);
GenericEntity<List<Map>> entity = new GenericEntity<List<Map>>(result) {};
Response response = Response.ok(entity).build();
return response;
}
}
這是行不通的,我收到的異常如下所示:
Exception in thread "main" org.glassfish.jersey.message.internal.MessageBodyProviderNotFoundException: MessageBodyReader not found for media type=application/json, type=class java.util.ArrayList, genericType=java.util.ArrayList<java.util.Map>.
at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor$TerminalReaderInterceptor.aroundReadFrom(ReaderInterceptorExecutor.java:231)
at org.glassfish.jersey.message.internal.ReaderInterceptorExecutor.proceed(ReaderInterceptorExecutor.java:155)
at org.glassfish.jersey.message.internal.MessageBodyFactory.readFrom(MessageBodyFactory.java:1085)
at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:874)
at org.glassfish.jersey.message.internal.InboundMessageContext.readEntity(InboundMessageContext.java:834)
at org.glassfish.jersey.client.ClientResponse.readEntity(ClientResponse.java:368)
at org.glassfish.jersey.client.InboundJaxrsResponse$2.call(InboundJaxrsResponse.java:126)
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:228)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:419)
at org.glassfish.jersey.client.InboundJaxrsResponse.runInScopeIfPossible(InboundJaxrsResponse.java:267)
at org.glassfish.jersey.client.InboundJaxrsResponse.readEntity(InboundJaxrsResponse.java:123)
at ls3test.Ls3TransmissionTest.main(Ls3TransmissionTest.java:89)
Ls3TransmissionTest.java:89是ObjectWriter ow = new ObjectMapper().writer().withDefaultPrettyPrinter();
我現在花了很多時間對這個問題進行研究,但是找不到適合的例子。 我想念什么? 任何幫助或提示,我們將不勝感激!
您可以發送地圖。 像這樣
Map<String, Object> map = new HashMap<>();
map.put("data", entity);
Response.ok(map).build();
return Response;
無法看到為什么需要用GenericEntity包裝列表。 如下所示的簡單方法將起作用:
@SuppressWarnings("rawtypes")
@GET
@Path("/{petrinets}/{k}/{theta}")
@Produces(MediaType.APPLICATION_JSON)
public Response ls3execute(@PathParam("petrinets") String petrinetNames, @PathParam("k") int k,
@PathParam("theta") float theta) {
//[... get all the relevant files from the MongoDB ...]
List<Map> result;
Ls3Algorithm ls3Algorithm = new Ls3Algorithm();
result = ls3Algorithm.execute(new File("petrinetze").getAbsolutePath(), k, theta);
Response response = Response.ok(result).build();
return response;
}
在客戶端,
String result = response.readEntity(String.class);
return result;
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