Java调用Http/Https接口(6)--RestTemplate调用Http/Https接口

RestTemplate是Spring提供的用于访问Http接口的客户端，提供同步的API；在将来的Spring版本中可能会过时，将逐渐被WebClient替代。文中所使用到的软件版本：Java 1.8.0_191、SpringBoot 2.2.1.RELEASE。

1、服务端

参见Java调用Http接口(1)--编写服务端 

2、调用Http接口

2.1、GET请求

    public static void get() {
        try {
            String requestPath = "http://localhost:8080/demo/httptest/getUser?userId=1000&userName=李白";
            RestTemplate template = new RestTemplate();
            //System.out.println(template.getMessageConverters());
            //第二个为StringHttpMessageConverter
            template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
            ResponseEntity<String> response = template.getForEntity(requestPath, String.class);
            System.out.println("get返回状态：" + response.getStatusCode());
            System.out.println("get返回结果：" + response.getBody());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

2.2、POST请求(发送键值对数据）

    public static void post() {
        String requestPath = "http://localhost:8080/demo/httptest/getUser";
        RestTemplate template = new RestTemplate();
        template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
        MultiValueMap<String, String> map = new LinkedMultiValueMap <String, String>();
        map.add("userId", "1000");
        map.add("userName", "李白");
        ResponseEntity<String> response = template.postForEntity(requestPath, map, String.class);
        System.out.println("post返回状态：" + response.getStatusCode());
        System.out.println("post返回结果：" + response.getBody());
    }

2.3、POST请求(发送JSON数据）

    public static void post2() {
        String requestPath = "http://localhost:8080/demo/httptest/addUser";
        RestTemplate template = new RestTemplate();
        template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
        
        String param = "{\"userId\": \"1001\",\"userName\":\"杜甫\"}";
        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Type", "application/json");
        HttpEntity<String> entity =  new HttpEntity<String>(param, headers);
        ResponseEntity<String> response = template.postForEntity(requestPath, entity, String.class);
        System.out.println("post json返回状态：" + response.getStatusCode());
        System.out.println("post json返回结果：" + response.getBody());
    }

2.4、上传文件

    public static void upload() {
        String requestPath = "http://localhost:8080/demo/httptest/upload";
        RestTemplate template = new RestTemplate();
        template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Type", "file/*");
        HttpEntity<FileSystemResource> entity =  new HttpEntity<FileSystemResource>(new FileSystemResource("d:/a.jpg"), headers);
        
        ResponseEntity<String> response = template.postForEntity(requestPath, entity, String.class);
        System.out.println("upload返回状态：" + response.getStatusCode());
        System.out.println("upload返回结果：" + response.getBody());
    }

2.5、上传文件及发送键值对数据

    public static void mulit() {
        String requestPath = "http://localhost:8080/demo/httptest/multi";
        RestTemplate template = new RestTemplate();
        template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
        MultiValueMap<String, Object> map = new LinkedMultiValueMap <String, Object>();
        map.add("param1", "参数1");
        map.add("param2", "参数2");
        map.add("file", new FileSystemResource("d:/a.jpg"));
        ResponseEntity<String> response = template.postForEntity(requestPath, map, String.class);
        System.out.println("mulit返回状态：" + response.getStatusCode());
        System.out.println("mulit返回结果：" + response.getBody());
    }

2.6、完整例子

package com.abc.demo.http.client;

import java.nio.charset.Charset;

import org.springframework.core.io.FileSystemResource;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpHeaders;
import org.springframework.http.ResponseEntity;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.client.RestTemplate;

/**
 * 
 * 通过RestTemplate调用Http接口
 *
 */
public class RestTemplateCase {
    /**
     *  GET请求
     */
    public static void get() {
        try {
            String requestPath = "http://localhost:8080/demo/httptest/getUser?userId=1000&userName=李白";
            RestTemplate template = new RestTemplate();
            //System.out.println(template.getMessageConverters());
            //第二个为StringHttpMessageConverter
            template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
            ResponseEntity<String> response = template.getForEntity(requestPath, String.class);
            System.out.println("get返回状态：" + response.getStatusCode());
            System.out.println("get返回结果：" + response.getBody());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    /**
     *  POST请求(发送键值对数据)
     */
    public static void post() {
        String requestPath = "http://localhost:8080/demo/httptest/getUser";
        RestTemplate template = new RestTemplate();
        template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
        MultiValueMap<String, String> map = new LinkedMultiValueMap <String, String>();
        map.add("userId", "1000");
        map.add("userName", "李白");
        ResponseEntity<String> response = template.postForEntity(requestPath, map, String.class);
        System.out.println("post返回状态：" + response.getStatusCode());
        System.out.println("post返回结果：" + response.getBody());
    }
    
    /**
     *  POST请求(发送json数据)
     */
    public static void post2() {
        String requestPath = "http://localhost:8080/demo/httptest/addUser";
        RestTemplate template = new RestTemplate();
        template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
        
        String param = "{\"userId\": \"1001\",\"userName\":\"杜甫\"}";
        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Type", "application/json");
        HttpEntity<String> entity =  new HttpEntity<String>(param, headers);
        ResponseEntity<String> response = template.postForEntity(requestPath, entity, String.class);
        System.out.println("post json返回状态：" + response.getStatusCode());
        System.out.println("post json返回结果：" + response.getBody());
    }
    
    /**
     * 上传文件
     */
    public static void upload() {
        String requestPath = "http://localhost:8080/demo/httptest/upload";
        RestTemplate template = new RestTemplate();
        template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Type", "file/*");
        HttpEntity<FileSystemResource> entity =  new HttpEntity<FileSystemResource>(new FileSystemResource("d:/a.jpg"), headers);
        
        ResponseEntity<String> response = template.postForEntity(requestPath, entity, String.class);
        System.out.println("upload返回状态：" + response.getStatusCode());
        System.out.println("upload返回结果：" + response.getBody());
    }
    
    /**
     * 上传文件及发送键值对数据
     */
    public static void mulit() {
        String requestPath = "http://localhost:8080/demo/httptest/multi";
        RestTemplate template = new RestTemplate();
        template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
        MultiValueMap<String, Object> map = new LinkedMultiValueMap <String, Object>();
        map.add("param1", "参数1");
        map.add("param2", "参数2");
        map.add("file", new FileSystemResource("d:/a.jpg"));
        ResponseEntity<String> response = template.postForEntity(requestPath, map, String.class);
        System.out.println("mulit返回状态：" + response.getStatusCode());
        System.out.println("mulit返回结果：" + response.getBody());
    }
    
    public static void main(String[] args) {
        get();
        post();
        post2();
        upload();
        mulit();
    }
}

3、调用Https接口

与调用Http接口不一样的部分主要在设置ssl部分，设置方法是扩展SimpleClientHttpRequestFactory并在prepareConnection方法中进行ssl的设置；ssl的设置与HttpsURLConnection很相似(参见Java调用Http/Https接口(2)--HttpURLConnection/HttpsURLConnection调用Http/Https接口)；下面用GET请求来演示ssl的设置，其他调用方式类似。

package com.abc.demo.http.client;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.nio.charset.Charset;
import java.security.KeyStore;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.KeyManager;
import javax.net.ssl.KeyManagerFactory;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManager;
import javax.net.ssl.TrustManagerFactory;
import javax.net.ssl.X509TrustManager;

import org.springframework.http.ResponseEntity;
import org.springframework.http.client.SimpleClientHttpRequestFactory;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.web.client.RestTemplate;

import com.abc.demo.common.util.FileUtil;

/**
 * 通过RestTemplate调用Https接口
 */
public class RestTemplateHttpsCase {
    public static void main(String[] args) {
        try {
            /*
             * 请求有权威证书的地址
             */
            String requestPath = "https://www.baidu.com/";
            RestTemplate template = new RestTemplate();
            template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
            ResponseEntity<String> response = template.getForEntity(requestPath, String.class);
            System.out.println("get1返回结果：" + response.getBody());
            
            /*
             * 请求自定义证书的地址
             */
            //获取信任证书库
            KeyStore trustStore = getkeyStore("jks", "d:/temp/cacerts", "123456");
            
            //不需要客户端证书
            requestPath = "https://10.49.196.10:9010/myservice";
            template = new RestTemplate(new HttpsClientRequestFactory(trustStore));
            template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
            response = template.getForEntity(requestPath, String.class);
            System.out.println("get2返回结果：" + response.getBody());
            
            //需要客户端证书，客户端证书可以是用 keytool 生成的 pks12 格式密钥库，也可以是用 OpenSSL 生成的 pkcs12 格式证书。
            requestPath = "https://10.49.196.10:9016/myservice";
            KeyStore keyStore = getkeyStore("pkcs12", "d:/client.p12", "123456");
            template = new RestTemplate(new HttpsClientRequestFactory(keyStore, "123456", trustStore));
            template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("UTF-8")));
            response = template.getForEntity(requestPath, String.class);
            System.out.println("get3返回结果：" + response.getBody());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    /**
     * 获取证书
     * @return
     */
    private static KeyStore getkeyStore(String type, String filePath, String password) {
        KeyStore keySotre = null;
        FileInputStream in = null;
        try {
            keySotre = KeyStore.getInstance(type);
            in = new FileInputStream(new File(filePath));
            keySotre.load(in, password.toCharArray());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            FileUtil.close(in);
        }
        return keySotre;
    }
    
    /**
     * 扩展SimpleClientHttpRequestFactory以支持Https
     */
    private static class HttpsClientRequestFactory extends SimpleClientHttpRequestFactory {
        private KeyStore keyStore;
        private String keyStorePassword;
        private KeyStore trustStore;
        
        public HttpsClientRequestFactory(KeyStore keyStore, String keyStorePassword, KeyStore trustStore) {
            this.keyStore = keyStore;
            this.keyStorePassword = keyStorePassword;
            this.trustStore = trustStore;
        }
        
        public HttpsClientRequestFactory(KeyStore trustStore) {
            this.trustStore = trustStore;
        }
        
        @Override
        protected void prepareConnection(HttpURLConnection connection, String httpMethod) throws IOException {
            try {
                if (!(connection instanceof HttpsURLConnection)) {
                    throw new RuntimeException("An instance of HttpsURLConnection is expected");
                }
                HttpsURLConnection httpsConnection = (HttpsURLConnection) connection;

                KeyManager[] keyManagers = null;
                TrustManager[] trustManagers = null;
                if (this.keyStore != null) {
                    KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance("SunX509");
                    keyManagerFactory.init(keyStore, keyStorePassword.toCharArray());
                    keyManagers = keyManagerFactory.getKeyManagers();
                }
                if (this.trustStore != null) {
                    TrustManagerFactory trustManagerFactory = TrustManagerFactory.getInstance("SunX509");
                    trustManagerFactory.init(trustStore);
                    trustManagers = trustManagerFactory.getTrustManagers();
                } else {
                    trustManagers = new TrustManager[] { new DefaultTrustManager()};
                }
                
                SSLContext sslContext = SSLContext.getInstance("TLS");
                sslContext.init(keyManagers, trustManagers, null);
                httpsConnection.setSSLSocketFactory(sslContext.getSocketFactory());
                //验证URL的主机名和服务器的标识主机名是否匹配
                httpsConnection.setHostnameVerifier(new HostnameVerifier() {
                    @Override
                    public boolean verify(String s, SSLSession sslSession) {
                        //if ("xxx".equals(hostname)) {
                        //    return true;
                        //} else {
                        //    return false;
                        //}
                        return true;
                    }
                });

                super.prepareConnection(httpsConnection, httpMethod);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    
    private static final class DefaultTrustManager implements X509TrustManager {
        @Override
        public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
        }

        @Override
        public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
        }

        @Override
        public X509Certificate[] getAcceptedIssuers() {
            return null;
        }
    }
}

4、AsyncRestTemplate

该模板已过时，建议使用 WebClient 替代。