Use the netty http client to build an extensible HTTP request in the Java library
Use the netty http client to build an extensible HTTP request in the Java library
Introduction:
Netty is a high -performance asynchronous incident -driven network programming framework that is suitable for developing scalable network protocols and servers.Netty provides a powerful HTTPClient component that can be used to build HTTP requests in scalable Java class libraries.
1. Introduce dependencies
In the pom.xml of the class library, add the following dependencies:
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.63.Final</version>
</dependency>
2. Create HTTPCLIENT instance
In the class library, create an HTTPClient instance for sending HTTP requests.You can use a singles mode or other ways to manage this instance.
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.*;
import io.netty.util.CharsetUtil;
public class HttpClient {
private final EventLoopGroup group;
private final Bootstrap bootstrap;
public HttpClient() {
group = new NioEventLoopGroup();
bootstrap = new Bootstrap();
bootstrap.group(group)
.channel(NioSocketChannel.class)
.handler(new HttpClientInitializer());
}
public void sendRequest(String url) {
try {
Channel channel = bootstrap.connect(url, 80).sync().channel();
HttpRequest request = new DefaultHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, "/");
HttpHeaders headers = request.headers();
headers.set(HttpHeaderNames.HOST, url);
headers.set(HttpHeaderNames.CONNECTION, HttpHeaderValues.CLOSE);
channel.writeAndFlush(request);
channel.closeFuture().sync();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} finally {
group.shutdownGracefully();
}
}
}
3. Create httpclientinitializer
Create the HTTPClientInitializer class to configure the ChannelPipeline and add an HTTP processor.
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpClientCodec;
public class HttpClientInitializer extends ChannelInitializer<SocketChannel> {
@Override
protected void initChannel(SocketChannel ch) {
ChannelHandler codec = new HttpClientCodec();
ch.pipeline().addLast(codec);
ch.pipeline().addLast(new HttpClientHandler());
}
}
4. Create httpclientHandler
Create the HTTPClientHandler class to handle HTTP response.
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.HttpContent;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.HttpObject;
import io.netty.handler.codec.http.HttpResponse;
import io.netty.util.CharsetUtil;
public class HttpClientHandler extends SimpleChannelInboundHandler<HttpObject> {
private StringBuilder contentBuilder = new StringBuilder();
@Override
protected void channelRead0(ChannelHandlerContext ctx, HttpObject msg) {
if (msg instanceof HttpResponse) {
HttpResponse response = (HttpResponse) msg;
HttpHeaders headers = response.headers();
System.out.println("Status: " + response.status());
System.out.println("Version: " + response.protocolVersion());
System.out.println("Headers: " + headers);
if (!response.status().codeAsText().toString().equals("200")) {
ctx.close();
return;
}
}
if (msg instanceof HttpContent) {
HttpContent content = (HttpContent) msg;
ByteBuf buf = content.content();
if (buf.isReadable()) {
contentBuilder.append(buf.toString(CharsetUtil.UTF_8));
}
if (content instanceof LastHttpContent) {
String contentString = contentBuilder.toString();
System.out.println("Response Content: " + contentString);
contentBuilder.setLength(0);
ctx.close();
}
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
ctx.close();
}
}
5. Where to send HTTP requests, use the httpclient example to send a request.
public class Main {
public static void main(String[] args) {
HttpClient httpClient = new HttpClient();
httpClient.sendRequest("www.example.com");
}
}
Summarize:
The HTTP request in the scalable Java class library using netty http client is very simple. It only needs to create an HTTPClient instance and send a request.By adding appropriate processors, HTTP requests and responses can be handled.Netty provides high -performance and scalability, making it very easy to build a reliable network request.
