HttpClient实现远程调用

简单理解
远程调用,是我们在做项目的时候经常遇到的。EJB可以实现远程调用;Dubbo+ZK可以实现远程调用;Spring Cloude中使用Resttemplate和Feign均可实现远程调用。今天要总结的是HttpClient,他也可以实现远程调用。而且爬虫就是用HttpClient来访问互联网,然后将数据保存到本地,然后用jsonp来提取需要的信息。

使用
引用httpclient的依赖

<dependency>
            <groupId>org.apache.httpcomponentsgroupId>
            <artifactId>httpclientartifactId>
        dependency>

get请求

@Test
    public void testHttpGet() throws Exception {
        //第一步:把HttpClient使用的jar包添加到工程中。
        //第二步:创建一个HttpClient的测试类
        //第三步:创建测试方法。
        //第四步:创建一个HttpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        //第五步:创建一个HttpGet对象,需要制定一个请求的url
        HttpGet get = new HttpGet("http://www.sogou.com");
        //第六步:执行请求。
        CloseableHttpResponse response = httpClient.execute(get);
        //第七步:接收返回结果。HttpEntity对象。
        HttpEntity entity = response.getEntity();
        //第八步:取响应的内容。
        String html = EntityUtils.toString(entity);
        System.out.print(html);
        //第九步:关闭response、HttpClient。
        response.close();
        httpClient.close();
    }

运行后可返回搜狗主页面的html代码

post请求

@Test
    public void testHttpPost() throws Exception {       
        // 第一步:创建一个httpClient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        // 第二步:创建一个HttpPost对象。需要指定一个url
        HttpPost post = new HttpPost("http://localhost:8083/posttest.html");
        // 第三步:创建一个list模拟表单,list中每个元素是一个NameValuePair对象
        List formList = new ArrayList<>();
        formList.add(new BasicNameValuePair("name", "张三"));
        formList.add(new BasicNameValuePair("pass", "1243"));
        // 第四步:需要把表单包装到Entity对象中。StringEntity
        StringEntity entity = new UrlEncodedFormEntity(formList, "utf-8");
        post.setEntity(entity);
        // 第五步:执行请求。
        CloseableHttpResponse response = httpClient.execute(post);
        // 第六步:接收返回结果
        HttpEntity httpEntity = response.getEntity();
        String result = EntityUtils.toString(httpEntity);
        System.out.println(result);
        // 第七步:关闭流。
        response.close();
        httpClient.close();
    }

可以将httpclient封装成工具类,方便使用

public class HttpClientUtil {

    public static String doGet(String url, Map param) {

        // 创建Httpclient对象
        CloseableHttpClient httpclient = HttpClients.createDefault();

        String resultString = "";
        CloseableHttpResponse response = null;
        try {
            // 创建uri
            URIBuilder builder = new URIBuilder(url);
            if (param != null) {
                for (String key : param.keySet()) {
                    builder.addParameter(key, param.get(key));
                }
            }
            URI uri = builder.build();

            // 创建http GET请求
            HttpGet httpGet = new HttpGet(uri);

            // 执行请求
            response = httpclient.execute(httpGet);
            // 判断返回状态是否为200
            if (response.getStatusLine().getStatusCode() == 200) {
                resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null) {
                    response.close();
                }
                httpclient.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return resultString;
    }

    public static String doGet(String url) {
        return doGet(url, null);
    }

    public static String doPost(String url, Map param) {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        CloseableHttpResponse response = null;
        String resultString = "";
        try {
            // 创建Http Post请求
            HttpPost httpPost = new HttpPost(url);
            // 创建参数列表
            if (param != null) {
                List paramList = new ArrayList<>();
                for (String key : param.keySet()) {
                    paramList.add(new BasicNameValuePair(key, param.get(key)));
                }
                // 模拟表单
                UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
                httpPost.setEntity(entity);
            }
            // 执行http请求
            response = httpClient.execute(httpPost);
            resultString = EntityUtils.toString(response.getEntity(), "utf-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        return resultString;
    }

    public static String doPost(String url) {
        return doPost(url, null);
    }

    public static String doPostJson(String url, String json) {
        // 创建Httpclient对象
        CloseableHttpClient httpClient = HttpClients.createDefault();
        CloseableHttpResponse response = null;
        String resultString = "";
        try {
            // 创建Http Post请求
            HttpPost httpPost = new HttpPost(url);
            // 创建请求内容
            StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
            httpPost.setEntity(entity);
            // 执行http请求
            response = httpClient.execute(httpPost);
            resultString = EntityUtils.toString(response.getEntity(), "utf-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                response.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        return resultString;
    }
}

工具类 的使用
“`
@Service
public class ContentServiceImpl implements ContentService {

@Value("${REST_BASE_URL}")
private String REST_BASE_URL;
@Value("${REST_CONTENT_URL}")
private String REST_CONTENT_URL;
@Value("${REST_CONTENT_AD1_CID}")
private String REST_CONTENT_AD1_CID;

/**
 * 获得大广告位的内容
 */
@Override
public String getAd1List() {
    //调用服务获得数据
    //将路径放到配置文件
    //HttpClientUtil.doGet("http:localhost:8082/rest/content/89");
    String json = HttpClientUtil.doGet(REST_BASE_URL + REST_CONTENT_URL + REST_CONTENT_AD1_CID);
    //把json转换成java对象
    TaotaoResult taotaoResult = TaotaoResult.formatToList(json, TbContent.class);
    //取data属性,内容列表
    List contentList = (List) taotaoResult.getData();
    //把内容列表转换成AdNode列表
    List resultList = new ArrayList<>();
    for (TbContent tbContent : contentList) {
        AdNode node = new AdNode();
        node.setHeight(240);
        node.setWidth(670);
        node.setSrc(tbContent.getPic());

        node.setHeightB(240);
        node.setWidthB(550);
        node.setSrcB(tbContent.getPic2());

        node.setAlt(tbContent.getSubTitle());
        node.setHref(tbContent.getUrl());

        resultList.add(node);
    }
    //需要把resultList转换成json数据
    String resultJson = JsonUtils.objectToJson(resultList);
    return resultJson;

}

}

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