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HttpComponents HttpClient 简介

HttpClient属于Apache HttpComponents项目，基于HttpCore，支持HTTP代理实现，支持状态管理，连接管理，自定义结果处理等功能，代替原先的Commons HttpClient 3.x。

HttpClient是比较实用的Http请求客户端，相比HttpURLConnection来说封装性更好，也提供了许多用户自定义以及拓展的能力，下面简单来使用一下：

模拟服务

@RestController
@RequestMapping("/demo")
@SpringBootApplication
@Slf4j
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }

    private List<Foo> foos = new CopyOnWriteArrayList<>();

    @GetMapping("/list")
    public ResponseEntity list(@RequestParam(value = "name") String name) {
        log.info("accept a list request...");
        return ResponseEntity.ok(foos.stream().filter(i -> i.getName().equals(name)).collect(Collectors.toList()));
    }

    @PostMapping
    public ResponseEntity create(@RequestBody Foo foo) {
        log.info("accept create request,foo:{}", foo);
        foos.add(foo);
        return ResponseEntity.ok(foo);
    }

    @GetMapping("/error")
    public ResponseEntity error() {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("error");
    }

    @GetMapping("/redirect")
    public ResponseEntity redirect() {
        return ResponseEntity.status(HttpStatus.FOUND).header(HttpHeaders.LOCATION, "http://www.baidu.com").build();
    }


    @Data
    @AllArgsConstructor
    public static class Foo {
        private String name;
        private int age;
    }
}

发起POST请求

//request body
Map<String, String> foo = new HashMap<>();
foo.put("name", "HTTP");
foo.put("age", "18");

HttpUriRequest request = RequestBuilder.post().setUri("http://localhost:8080/demo")
    .setEntity(new StringEntity(JSONObject.toJSONString(foo), ContentType.APPLICATION_JSON)).build();

CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = httpClient.execute(request);
int statusCode = response.getStatusLine().getStatusCode();
//错误判断
if (statusCode >= 200 & statusCode < 300) {
    String body = IOUtils.toString(response.getEntity().getContent(), StandardCharsets.UTF_8.name());
    log.info("请求结果:{}", body);
} else {
    log.error("请求错误，statusCode={}", statusCode);
}

发起Get请求

HttpUriRequest request = RequestBuilder.get().setUri("http://localhost:8080/demo/list")
    .addParameter("name", "HTTP").addHeader("Content-Type", "application/json").build();
        
//设置超时
RequestConfig requestConfig = RequestConfig.custom().setConnectTimeout(1000 * 5).build();

CloseableHttpClient httpClient = HttpClients.custom().setDefaultRequestConfig(requestConfig).build();

CloseableHttpResponse response = httpClient.execute(request);

System.out.println(response);
int statusCode = response.getStatusLine().getStatusCode();
if (statusCode >= 200 & statusCode < 300) {
    String body = IOUtils.toString(response.getEntity().getContent(), StandardCharsets.UTF_8.name());
    log.info("请求结果:{}", body);
} else {
    log.error("请求错误，statusCode={}", statusCode);
}

使用BasicResponseHandler处理结果

HttpUriRequest request = RequestBuilder.get().setUri("http://localhost:8080/demo/error")
    .addHeader("Content-Type", "application/json").build();
CloseableHttpClient httpClient = HttpClients.custom().build();
try {
    String response = httpClient.execute(request, new BasicResponseHandler());
    System.out.println(response);
} catch (HttpResponseException e) {
    log.error("error,code={},message={}", e.getStatusCode(), e.getMessage(), e);
}

设置超时

// 备注，socketTimeout指接收数据时的超时，connectTimeout指的是建立连接的超时
RequestConfig.custom()
                .setSocketTimeout(5 * 1000)//socket超时
                .setConnectTimeout(10 * 1000)//连接超时
                  .setConnectionRequestTimeout(5000)//从连接池获取连接的超时时间
                .build();

常用配置(官方例子)

/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.apache.http.examples.client;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.nio.charset.CodingErrorAction;
import java.util.Arrays;

import javax.net.ssl.SSLContext;

import org.apache.http.Consts;
import org.apache.http.Header;
import org.apache.http.HttpHost;
import org.apache.http.HttpRequest;
import org.apache.http.HttpResponse;
import org.apache.http.ParseException;
import org.apache.http.client.CookieStore;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.config.AuthSchemes;
import org.apache.http.client.config.CookieSpecs;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.config.ConnectionConfig;
import org.apache.http.config.MessageConstraints;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.config.SocketConfig;
import org.apache.http.conn.DnsResolver;
import org.apache.http.conn.HttpConnectionFactory;
import org.apache.http.conn.ManagedHttpClientConnection;
import org.apache.http.conn.routing.HttpRoute;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.impl.DefaultHttpResponseFactory;
import org.apache.http.impl.client.BasicCookieStore;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.impl.conn.DefaultHttpResponseParser;
import org.apache.http.impl.conn.DefaultHttpResponseParserFactory;
import org.apache.http.impl.conn.ManagedHttpClientConnectionFactory;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.impl.conn.SystemDefaultDnsResolver;
import org.apache.http.impl.io.DefaultHttpRequestWriterFactory;
import org.apache.http.io.HttpMessageParser;
import org.apache.http.io.HttpMessageParserFactory;
import org.apache.http.io.HttpMessageWriterFactory;
import org.apache.http.io.SessionInputBuffer;
import org.apache.http.message.BasicHeader;
import org.apache.http.message.BasicLineParser;
import org.apache.http.message.LineParser;
import org.apache.http.ssl.SSLContexts;
import org.apache.http.util.CharArrayBuffer;
import org.apache.http.util.EntityUtils;

/**
 * This example demonstrates how to customize and configure the most common aspects
 * of HTTP request execution and connection management.
 */
public class ClientConfiguration {

    public final static void main(String[] args) throws Exception {

        // Use custom message parser / writer to customize the way HTTP
        // messages are parsed from and written out to the data stream.
        HttpMessageParserFactory<HttpResponse> responseParserFactory = new DefaultHttpResponseParserFactory() {

            @Override
            public HttpMessageParser<HttpResponse> create(
                SessionInputBuffer buffer, MessageConstraints constraints) {
                LineParser lineParser = new BasicLineParser() {

                    @Override
                    public Header parseHeader(final CharArrayBuffer buffer) {
                        try {
                            return super.parseHeader(buffer);
                        } catch (ParseException ex) {
                            return new BasicHeader(buffer.toString(), null);
                        }
                    }

                };
                return new DefaultHttpResponseParser(
                    buffer, lineParser, DefaultHttpResponseFactory.INSTANCE, constraints) {

                    @Override
                    protected boolean reject(final CharArrayBuffer line, int count) {
                        // try to ignore all garbage preceding a status line infinitely
                        return false;
                    }

                };
            }

        };
        HttpMessageWriterFactory<HttpRequest> requestWriterFactory = new DefaultHttpRequestWriterFactory();

        // Use a custom connection factory to customize the process of
        // initialization of outgoing HTTP connections. Beside standard connection
        // configuration parameters HTTP connection factory can define message
        // parser / writer routines to be employed by individual connections.
        HttpConnectionFactory<HttpRoute, ManagedHttpClientConnection> connFactory = new ManagedHttpClientConnectionFactory(
                requestWriterFactory, responseParserFactory);

        // Client HTTP connection objects when fully initialized can be bound to
        // an arbitrary network socket. The process of network socket initialization,
        // its connection to a remote address and binding to a local one is controlled
        // by a connection socket factory.

        // SSL context for secure connections can be created either based on
        // system or application specific properties.
        SSLContext sslcontext = SSLContexts.createSystemDefault();

        // Create a registry of custom connection socket factories for supported
        // protocol schemes.
        Registry<ConnectionSocketFactory> socketFactoryRegistry = RegistryBuilder.<ConnectionSocketFactory>create()
            .register("http", PlainConnectionSocketFactory.INSTANCE)
            .register("https", new SSLConnectionSocketFactory(sslcontext))
            .build();

        // Use custom DNS resolver to override the system DNS resolution.
        DnsResolver dnsResolver = new SystemDefaultDnsResolver() {

            @Override
            public InetAddress[] resolve(final String host) throws UnknownHostException {
                if (host.equalsIgnoreCase("myhost")) {
                    return new InetAddress[] { InetAddress.getByAddress(new byte[] {127, 0, 0, 1}) };
                } else {
                    return super.resolve(host);
                }
            }

        };

        // Create a connection manager with custom configuration.
        PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager(
                socketFactoryRegistry, connFactory, dnsResolver);

        // Create socket configuration
        SocketConfig socketConfig = SocketConfig.custom()
            .setTcpNoDelay(true)
            .build();
        // Configure the connection manager to use socket configuration either
        // by default or for a specific host.
        connManager.setDefaultSocketConfig(socketConfig);
        connManager.setSocketConfig(new HttpHost("somehost", 80), socketConfig);
        // Validate connections after 1 sec of inactivity
        connManager.setValidateAfterInactivity(1000);

        // Create message constraints
        MessageConstraints messageConstraints = MessageConstraints.custom()
            .setMaxHeaderCount(200)
            .setMaxLineLength(2000)
            .build();
        // Create connection configuration
        ConnectionConfig connectionConfig = ConnectionConfig.custom()
            .setMalformedInputAction(CodingErrorAction.IGNORE)
            .setUnmappableInputAction(CodingErrorAction.IGNORE)
            .setCharset(Consts.UTF_8)
            .setMessageConstraints(messageConstraints)
            .build();
        // Configure the connection manager to use connection configuration either
        // by default or for a specific host.
        connManager.setDefaultConnectionConfig(connectionConfig);
        connManager.setConnectionConfig(new HttpHost("somehost", 80), ConnectionConfig.DEFAULT);

        // Configure total max or per route limits for persistent connections
        // that can be kept in the pool or leased by the connection manager.
        connManager.setMaxTotal(100);
        connManager.setDefaultMaxPerRoute(10);
        connManager.setMaxPerRoute(new HttpRoute(new HttpHost("somehost", 80)), 20);

        // Use custom cookie store if necessary.
        CookieStore cookieStore = new BasicCookieStore();
        // Use custom credentials provider if necessary.
        CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
        // Create global request configuration
        RequestConfig defaultRequestConfig = RequestConfig.custom()
            .setCookieSpec(CookieSpecs.DEFAULT)
            .setExpectContinueEnabled(true)
            .setTargetPreferredAuthSchemes(Arrays.asList(AuthSchemes.NTLM, AuthSchemes.DIGEST))
            .setProxyPreferredAuthSchemes(Arrays.asList(AuthSchemes.BASIC))
            .build();

        // Create an HttpClient with the given custom dependencies and configuration.
        CloseableHttpClient httpclient = HttpClients.custom()
            .setConnectionManager(connManager)
            .setDefaultCookieStore(cookieStore)
            .setDefaultCredentialsProvider(credentialsProvider)
            .setProxy(new HttpHost("myproxy", 8080))
            .setDefaultRequestConfig(defaultRequestConfig)
            .build();

        try {
            HttpGet httpget = new HttpGet("http://httpbin.org/get");
            // Request configuration can be overridden at the request level.
            // They will take precedence over the one set at the client level.
            RequestConfig requestConfig = RequestConfig.copy(defaultRequestConfig)
                .setSocketTimeout(5000)
                .setConnectTimeout(5000)
                .setConnectionRequestTimeout(5000)
                .setProxy(new HttpHost("myotherproxy", 8080))
                .build();
            httpget.setConfig(requestConfig);

            // Execution context can be customized locally.
            HttpClientContext context = HttpClientContext.create();
            // Contextual attributes set the local context level will take
            // precedence over those set at the client level.
            context.setCookieStore(cookieStore);
            context.setCredentialsProvider(credentialsProvider);

            System.out.println("executing request " + httpget.getURI());
            CloseableHttpResponse response = httpclient.execute(httpget, context);
            try {
                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());
                System.out.println(EntityUtils.toString(response.getEntity()));
                System.out.println("----------------------------------------");

                // Once the request has been executed the local context can
                // be used to examine updated state and various objects affected
                // by the request execution.

                // Last executed request
                context.getRequest();
                // Execution route
                context.getHttpRoute();
                // Target auth state
                context.getTargetAuthState();
                // Proxy auth state
                context.getProxyAuthState();
                // Cookie origin
                context.getCookieOrigin();
                // Cookie spec used
                context.getCookieSpec();
                // User security token
                context.getUserToken();

            } finally {
                response.close();
            }
        } finally {
            httpclient.close();
        }
    }

}

总结

HttpClient是我们常用的Http客户端，了解熟悉API以及相关配置有利于我们更好的使用，一般场景下使用默认的配置都能满足要求，如果有特殊的要求也支持自定义配置。