我们有JAX RS实现，它需要发送回JSON输出。但是响应大小很大。和客户同步期望相同。
因此，我尝试使用StreamingOutput ...，但是客户端并没有真正获取大块数据。
以下是示例代码段:
服务器端
streamingOutput = new StreamingOutput() {
@Override
public void write(OutputStream out) throws IOException, WebApplicationException {
JsonGenerator jsonGenerator = mapper.getFactory().createGenerator(out);
jsonGenerator.writeStartArray();
for(int i=0; i < 10; i++) {
jsonGenerator.writeStartObject();
jsonGenerator.writeStringField("Response_State", "Response State - " + i);
jsonGenerator.writeStringField("Response_Report", "Response Report - " + i);
jsonGenerator.writeStringField("Error_details", "Error Details - " + i);
jsonGenerator.writeEndObject();;
jsonGenerator.flush();
try {
Thread.currentThread().sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
jsonGenerator.writeEndArray();
jsonGenerator.close();
}
};
return Response.status(200).entity(streamingOutput).build();
客户
HttpClient client = HttpClientBuilder.create().build();
HttpPost post = new HttpPost("http://localhost:8080/AccessData/FetchReport");
post.setHeader("Content-type", "application/json");
ResponseHandler<HttpResponse> responseHandler = new BasicResponseHandler();
StringEntity entity = new StringEntity(jsonRequest); //jsonRequest is request string
post.setEntity(entity);
HttpResponse response = client.execute(post);
BufferedReader buffReader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
JsonParser jsonParser = new JsonFactory().createParser(buffReader);
while(jsonParser.nextToken() != JsonToken.END_OBJECT) {
System.out.println(jsonParser.getCurrentName() + ":" + jsonParser.getCurrentValue());
}
String output;
while((output = buffReader.readLine()) != null) {
System.out.println(output);
}
在服务器端代码中，我将sleep调用只是为了模拟数据块之间的间隙。我需要的是，客户端应在服务器将其抛回时接收大块数据。
但是在这里，客户总是会得到完整的响应。
有什么解决办法吗？
提前致谢。
最佳答案
客户端似乎未正确实现:使用解析器读取对象的数组。
另外，我想建议读写数据传输对象，而不是逐级进行低级读写。
为了完整起见，下面是一个完整的草稿示例，该示例使用:Jersey 2.25.1，Jetty 9.2.14.v20151106。
常见的ResponseData类
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
public class ResponseData {
private final String responseState;
private final String responseReport;
private final String errorDetails;
@JsonCreator
public ResponseData(
@JsonProperty("Response_State") final String responseState,
@JsonProperty("Response_Report") final String responseReport,
@JsonProperty("Error_details") final String errorDetails) {
this.responseState = responseState;
this.responseReport = responseReport;
this.errorDetails = errorDetails;
}
public String getResponseState() {
return this.responseState;
}
public String getResponseReport() {
return this.responseReport;
}
public String getErrorDetails() {
return this.errorDetails;
}
@Override
public String toString() {
return String.format(
"ResponseData: responseState: %s; responseReport: %s; errorDetails: %s",
this.responseState,
this.responseReport,
this.errorDetails
);
}
}
服务
ServerProgram类import java.net.URI;
import org.glassfish.jersey.jackson.JacksonFeature;
import org.glassfish.jersey.jetty.JettyHttpContainerFactory;
import org.glassfish.jersey.server.ResourceConfig;
public class ServerProgram {
public static void main(final String[] args) {
final URI uri = URI.create("http://localhost:8080/");
final ResourceConfig resourceConfig = new ResourceConfig(TestResource.class);
resourceConfig.register(JacksonFeature.class);
JettyHttpContainerFactory.createServer(uri, resourceConfig);
}
}
TestResource类import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
import java.io.OutputStream;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.StreamingOutput;
@Path("/")
public class TestResource {
@GET
@Produces(MediaType.APPLICATION_JSON)
public Response getData() {
final StreamingOutput streamingOutput = new JsonStreamingOutput();
return Response.status(200).entity(streamingOutput).build();
}
private static class JsonStreamingOutput implements StreamingOutput {
@Override
public void write(final OutputStream outputStream) throws IOException, WebApplicationException {
final ObjectMapper objectMapper = new ObjectMapper();
final JsonFactory jsonFactory = objectMapper.getFactory();
try (final JsonGenerator jsonGenerator = jsonFactory.createGenerator(outputStream)) {
jsonGenerator.writeStartArray();
for (int i = 0; i < 10; i++) {
final ResponseData responseData = new ResponseData(
"Response State - " + i,
"Response Report - " + i,
"Error Details - " + i
);
jsonGenerator.writeObject(responseData);
jsonGenerator.flush();
try {
Thread.currentThread().sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
jsonGenerator.writeEndArray();
}
}
}
}
客户
ClientProgram类import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.ws.rs.client.Client;
import javax.ws.rs.client.ClientBuilder;
import javax.ws.rs.core.MediaType;
import org.glassfish.jersey.client.ClientProperties;
public class ClientProgram {
public static void main(final String[] args) throws IOException {
Client client = null;
try {
client = ClientBuilder.newClient();
client.property(ClientProperties.READ_TIMEOUT, 10000);
try (final InputStream inputStream = client
.target("http://localhost:8080/")
.request(MediaType.APPLICATION_JSON)
.get(InputStream.class);
final BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream)) {
processStream(bufferedInputStream);
}
} finally {
if (client != null) {
client.close();
}
}
}
private static void processStream(final InputStream inputStream) throws IOException {
final ObjectMapper objectMapper = new ObjectMapper();
final JsonFactory jsonFactory = objectMapper.getFactory();
try (final JsonParser jsonParser = jsonFactory.createParser(inputStream)) {
final JsonToken arrayToken = jsonParser.nextToken();
if (arrayToken == null) {
// TODO: Return or throw exception.
return;
}
if (!JsonToken.START_ARRAY.equals(arrayToken)) {
// TODO: Return or throw exception.
return;
}
// Iterate through the objects of the array.
while (JsonToken.START_OBJECT.equals(jsonParser.nextToken())) {
final ResponseData responseData = jsonParser.readValueAs(ResponseData.class);
System.out.println(responseData);
}
}
}
}
希望这可以帮助。
关于java - REST流JSON输出，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/45635739/