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Apache HttpClientの例

Apache HttpClientの例

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この記事では、Apache HttpClientを使用してHTTP GET / POSTリクエスト、JSON、認証、タイムアウト、リダイレクトを送信する方法と、よく使用されるいくつかの例を示します。

P.S Tested with HttpClient 4.5.10

pom.xml

    
        org.apache.httpcomponents
        httpclient
        4.5.10

1. GETリクエストを送信

1.1 Close manually.

HttpClientExample1_1.java

package com.example.http;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHeaders;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpClientExample1_1 {

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

        CloseableHttpClient httpClient = HttpClients.createDefault();

        try {

            HttpGet request = new HttpGet("https://httpbin.org/get");

            // add request headers
            request.addHeader("custom-key", "example");
            request.addHeader(HttpHeaders.USER_AGENT, "Googlebot");

            CloseableHttpResponse response = httpClient.execute(request);

            try {

                // Get HttpResponse Status
                System.out.println(response.getProtocolVersion());              // HTTP/1.1
                System.out.println(response.getStatusLine().getStatusCode());   // 200
                System.out.println(response.getStatusLine().getReasonPhrase()); // OK
                System.out.println(response.getStatusLine().toString());        // HTTP/1.1 200 OK

                HttpEntity entity = response.getEntity();
                if (entity != null) {
                    // return it as a String
                    String result = EntityUtils.toString(entity);
                    System.out.println(result);
                }

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

    }

}

1.2 Close with try-with-resources.

HttpClientExample1_2.java

package com.example.http;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHeaders;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpClientExample1_2 {

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

        HttpGet request = new HttpGet("https://httpbin.org/get");

        // add request headers
        request.addHeader("custom-key", "example");
        request.addHeader(HttpHeaders.USER_AGENT, "Googlebot");

        try (CloseableHttpClient httpClient = HttpClients.createDefault();
             CloseableHttpResponse response = httpClient.execute(request)) {

            // Get HttpResponse Status
            System.out.println(response.getProtocolVersion());              // HTTP/1.1
            System.out.println(response.getStatusLine().getStatusCode());   // 200
            System.out.println(response.getStatusLine().getReasonPhrase()); // OK
            System.out.println(response.getStatusLine().toString());        // HTTP/1.1 200 OK

            HttpEntity entity = response.getEntity();
            if (entity != null) {
                // return it as a String
                String result = EntityUtils.toString(entity);
                System.out.println(result);
            }

        }

    }

}

2. 通常のPOSTリクエストを送信

HttpClientExample2_1.java

package com.example.http;

import org.apache.http.HttpHeaders;
import org.apache.http.NameValuePair;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class HttpClientExample2_1 {

    public static void main(String[] args) {

        try {
            String result = sendPOST("https://httpbin.org/post");
            System.out.println(result);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    private static String sendPOST(String url) throws IOException {

        String result = "";
        HttpPost post = new HttpPost(url);

        // add request parameters or form parameters
        List urlParameters = new ArrayList<>();
        urlParameters.add(new BasicNameValuePair("username", "abc"));
        urlParameters.add(new BasicNameValuePair("password", "123"));
        urlParameters.add(new BasicNameValuePair("custom", "secret"));

        post.setEntity(new UrlEncodedFormEntity(urlParameters));

        try (CloseableHttpClient httpClient = HttpClients.createDefault();
             CloseableHttpResponse response = httpClient.execute(post)){

            result = EntityUtils.toString(response.getEntity());
        }

        return result;
    }

}

3. JSON POSTリクエストを送信

3.1 Send a POST request with JSON formatted data. キーは、JSON形式の日付をStringEntityに渡します。

HttpClientExample3_1.java

package com.example.http;

import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpClientExample3_1 {

    public static void main(String[] args) {

        try {
            String result = sendPOST("https://httpbin.org/post");
            System.out.println(result);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    private static String sendPOST(String url) throws IOException {

        String result = "";
        HttpPost post = new HttpPost(url);

        StringBuilder json = new StringBuilder();
        json.append("{");
        json.append("\"name\":\"example\",");
        json.append("\"notes\":\"hello\"");
        json.append("}");

        // send a JSON data
        post.setEntity(new StringEntity(json.toString()));

        try (CloseableHttpClient httpClient = HttpClients.createDefault();
             CloseableHttpResponse response = httpClient.execute(post)) {

            result = EntityUtils.toString(response.getEntity());
        }

        return result;
    }

}

3.2 Send a POST request to Cloudflare API to block an IP address. ヘッダーの認証。

HttpClientExample3_2.java

package com.example.http;

import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpClientExample3_2 {

    public static void main(String[] args) {

        try {
            String result = blockIP("1.1.1.1");
            System.out.println(result);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    private static String blockIP(String ip) throws IOException {

        String result = "";

        HttpPost post = new HttpPost("https://api.cloudflare.com/client/v4/user/firewall/access_rules/rules");
        post.addHeader("content-type", "application/json");
        post.addHeader("X-Auth-Email", "email");
        post.addHeader("X-Auth-Key", "token123");

        String block = "{\"target\":\"ip\",\"value\":\"" + ip + "\"}";

        StringBuilder entity = new StringBuilder();
        entity.append("{");
        entity.append("\"mode\":\"block\",");
        entity.append("\"configuration\":" + block + ",");
        entity.append("\"notes\":\"hello\"");
        entity.append("}");

        // send a JSON data
        post.setEntity(new StringEntity(entity.toString()));

        try (CloseableHttpClient httpClient = HttpClients.createDefault();
             CloseableHttpResponse response = httpClient.execute(post)) {

            result = EntityUtils.toString(response.getEntity());
        }

        return result;

    }

}

4. HTTP基本認証

HttpClientExample4_1.java

package com.example.http;

import org.apache.http.HttpEntity;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpClientExample4_1 {

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

        HttpGet request = new HttpGet("http://localhost:8080/books");

        CredentialsProvider provider = new BasicCredentialsProvider();
        provider.setCredentials(
                AuthScope.ANY,
                new UsernamePasswordCredentials("user", "password")
        );

        try (CloseableHttpClient httpClient = HttpClientBuilder.create()
                .setDefaultCredentialsProvider(provider)
                .build();
             CloseableHttpResponse response = httpClient.execute(request)) {

            // 401 if wrong user/password
            System.out.println(response.getStatusLine().getStatusCode());

            HttpEntity entity = response.getEntity();
            if (entity != null) {
                // return it as a String
                String result = EntityUtils.toString(entity);
                System.out.println(result);
            }

        }

    }

}

これを読んでください–Apache HttpClient Basic Authentication Examples

5. FAQs

5.1 Disabled Redirect.

HttpClientExample5_1.java

package com.example.customer;

import org.apache.http.HttpEntity;
import org.apache.http.HttpHeaders;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;

import java.io.IOException;

public class HttpClientExample5_1 {

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

        HttpGet request = new HttpGet("https://t.co/calv72DH8f");
        request.addHeader(HttpHeaders.USER_AGENT, "Googlebot");

        try (CloseableHttpClient httpClient = HttpClientBuilder.create().disableRedirectHandling().build();
             CloseableHttpResponse response = httpClient.execute(request)) {

            // Get HttpResponse Status
            System.out.println(response.getProtocolVersion());              // HTTP/1.1
            System.out.println(response.getStatusLine().getStatusCode());   // 301
            System.out.println(response.getStatusLine().getReasonPhrase()); // Moved Permanently
            System.out.println(response.getStatusLine().toString());        // HTTP/1.1 301 Moved Permanently

            HttpEntity entity = response.getEntity();
            if (entity != null) {
                // return it as a String
                String result = EntityUtils.toString(entity);
                System.out.println(result);
            }

        }

    }

}

5.2 Connection time out on request level.

    HttpGet request = new HttpGet("https://httpbin.org/get");

    // 5 seconds timeout
    RequestConfig requestConfig = RequestConfig.custom()
            .setConnectionRequestTimeout(5000)
            .setConnectTimeout(5000)
            .setSocketTimeout(5000)
            .build();

    request.setConfig(requestConfig);

    try (CloseableHttpClient httpClient = HttpClients.createDefault();
         CloseableHttpResponse response = httpClient.execute(request)) {

        //...

    }

5.3 Connection time out on client level.

    HttpGet request = new HttpGet("https://httpbin.org/get");

    // 5 seconds timeout
    RequestConfig requestConfig = RequestConfig.custom()
            .setConnectionRequestTimeout(5000)
            .setConnectTimeout(5000)
            .setSocketTimeout(5000)
            .build();

    //request.setConfig(requestConfig);

    try (CloseableHttpClient httpClient = HttpClientBuilder.create()
            .setDefaultRequestConfig(requestConfig)
            .build();
         CloseableHttpResponse response = httpClient.execute(request)) {

        //...

    }

5.4 Configure a proxy server. HttpClient proxy configurationを読む 

    HttpGet request = new HttpGet("https://httpbin.org/get");

    RequestConfig requestConfig = RequestConfig.custom()
            .setProxy(new HttpHost("company.proxy.url", 8080))
            .build();

    request.setConfig(requestConfig);

    try (CloseableHttpClient httpClient = HttpClients.createDefault();
         CloseableHttpResponse response = httpClient.execute(request)) {

        //...

    }

5.5 Turn on cookie. HTTP cookiesを読む 

    HttpGet request = new HttpGet("https://httpbin.org/get");

    RequestConfig requestConfig = RequestConfig.custom()
            .setCookieSpec(CookieSpecs.DEFAULT)
            .build();

    request.setConfig(requestConfig);

    try (CloseableHttpClient httpClient = HttpClients.createDefault();
     CloseableHttpResponse response = httpClient.execute(request)) {

    //...

    }

5.6 Get response header and also the media type.

    try (CloseableHttpClient httpClient = HttpClients.createDefault();
         CloseableHttpResponse response = httpClient.execute(request)) {

        HttpEntity entity = response.getEntity();
        Header headers = entity.getContentType();
        System.out.println(headers);

        //...
    }

サンプル 

Content-Type: application/json
{
  "args": {},
  "headers": {
    "Accept-Encoding": "gzip,deflate",
    "Custom-Key": "example",
    "Host": "httpbin.org",
    "User-Agent": "Googlebot"
  },
  "origin": "202.168.71.227, 202.168.71.227",
  "url": "https://httpbin.org/get"
}

参考文献

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