HttpClient 入门教程学习

HttpClient简介

HttpClient是基于HttpCore的HTTP/1.1兼容的HTTP代理实现。 它还为客户端认证，HTTP状态管理和HTTP连接管理提供可重用组件。 HttpComponents Client是Commons HttpClient 3.x的继任者和替代者。 强烈建议Commons HttpClient的用户进行升级。

HttpClient HTTP Get请求

/**
 * httpClient Get请求
 */
public static void main(String[] args) throws IOException {
    try (CloseableHttpClient httpclient = HttpClients.createDefault()) {

        //第一步 配置 Get 请求 Url
        HttpGet httpget = new HttpGet("http://httpbin.org/get");

        //第二步 创建一个自定义的 response handler
        ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
            @Override
            public String handleResponse(HttpResponse response) throws IOException {
                int status = response.getStatusLine().getStatusCode();
                if (status >= 200 && status < 300) {
                    HttpEntity entity = response.getEntity();
                    return entity != null ? EntityUtils.toString(entity) : null;
                } else {
                    throw new ClientProtocolException("Unexpected response status: " + status);
                }
            }
        };

        //第三步 执行请求
        String responseBody = httpclient.execute(httpget, responseHandler);
        System.out.println("----------------------------------------");
        System.out.println(responseBody);
    }
}

HttpClient HTTP Post请求

/**
 * httpClient Post请求
 */
public static void main(String[] args) throws IOException {

    try (CloseableHttpClient httpclient = HttpClients.createDefault()) {

        //第一步 配置 Post 请求 Url
        HttpPost httpPost = new HttpPost("http://httpbin.org/post");

        // 装配post请求参数
        List<BasicNameValuePair> list = new ArrayList<BasicNameValuePair>();
        list.add(new BasicNameValuePair("age", "20"));  //请求参数
        list.add(new BasicNameValuePair("name", "zhangsan")); //请求参数
        httpPost.setEntity(new StringEntity("Hello, World"));

        /*
            设置post请求参数
            两个方式:具体参考UrlEncodedFormEntity和StringEntity区别
        */
        httpPost.setEntity(new UrlEncodedFormEntity(list, "UTF-8"));
        //httpPost.setEntity(new StringEntity(list.toString(), "UTF-8"));

        //第二步 创建一个自定义的 response handler
        ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
            @Override
            public String handleResponse(HttpResponse response) throws IOException {
                int status = response.getStatusLine().getStatusCode();
                if (status >= 200 && status < 300) {
                    HttpEntity entity = response.getEntity();
                    return entity != null ? EntityUtils.toString(entity) : null;
                } else {
                    throw new ClientProtocolException("Unexpected response status: " + status);
                }
            }
        };

        //第三步 执行请求
        String responseBody = httpclient.execute(httpPost, responseHandler);
        System.out.println("----------------------------------------");
        System.out.println(responseBody);
    }
}

HttpClient HTTP Put请求

/**
 * httpClient Put 请求
 */
public static void main(String[] args) throws IOException {

    try (CloseableHttpClient httpclient = HttpClients.createDefault()) {

        //第一步 配置 Post 请求 Url
        HttpPut httpPut = new HttpPut("http://httpbin.org/put");

        //设置post请求参数
        httpPut.setEntity(new StringEntity("Hello, World"));

        //第二步 创建一个自定义的 response handler
        ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
            @Override
            public String handleResponse(HttpResponse response) throws IOException {
                int status = response.getStatusLine().getStatusCode();
                if (status >= 200 && status < 300) {
                    HttpEntity entity = response.getEntity();
                    return entity != null ? EntityUtils.toString(entity) : null;
                } else {
                    throw new ClientProtocolException("Unexpected response status: " + status);
                }
            }
        };

        String responseBody = httpclient.execute(httpPut, responseHandler);
        System.out.println("----------------------------------------");
        System.out.println(responseBody);
    }

}

HttpClient HTTP Delete请求

/**
 * httpClient Delete 请求
 */
public static void main(String[] args) throws IOException {

    try (CloseableHttpClient httpclient = HttpClients.createDefault()) {

        //第一步 配置 Delete 请求 Url
        HttpDelete httpDelete = new HttpDelete("http://httpbin.org/delete");

        System.out.println("Executing request " + httpDelete.getRequestLine());

        //第二步 创建一个自定义的 response handler
        ResponseHandler<String> responseHandler = new ResponseHandler<String>() {
            @Override
            public String handleResponse(HttpResponse response) throws IOException {
                int status = response.getStatusLine().getStatusCode();
                if (status >= 200 && status < 300) {
                    HttpEntity entity = response.getEntity();
                    return entity != null ? EntityUtils.toString(entity) : null;
                } else {
                    throw new ClientProtocolException("Unexpected response status: " + status);
                }
            }
        };

        String responseBody = httpclient.execute(httpDelete, responseHandler);
        System.out.println("----------------------------------------");
        System.out.println(responseBody);
    }
}

HttpClient自定义HTTP Header

/**
 * HttpClient自定义HTTP头
 */
public static void main(String[] args)throws IOException {
    // 创建自定义 http headers
    List<Header> defaultHeaders = Arrays.asList(
            new BasicHeader("X-Default-Header", "default header httpclient"));

    // 设置自定义 http headers
    CloseableHttpClient httpclient = HttpClients
            .custom()
            .setDefaultHeaders(defaultHeaders)
            .build();

    try {

        // 配置超时时间
        RequestConfig requestConfig = RequestConfig.custom()
                .setConnectTimeout(5000)   //设置连接超时时间
                .setConnectionRequestTimeout(5000) // 设置请求超时时间
                .setSocketTimeout(5000)
                .setRedirectsEnabled(true)//默认允许自动重定向
                .build();

        // 创建自定义 http headers on the http request
        HttpUriRequest request = RequestBuilder.get()
                .setUri("http://httpbin.org/headers")
                .setHeader(HttpHeaders.CONTENT_TYPE, "application/json")
                .setHeader(HttpHeaders.FROM, "https://memorynotfound.com")
                .setHeader("X-Custom-Header", "custom header http request")
                .setConfig(requestConfig)
                .build();

        System.out.println("Executing request " + request.getRequestLine());

        // 创建自定义 response handler
        ResponseHandler<String> responseHandler = response -> {
            int status = response.getStatusLine().getStatusCode();
            if (status >= 200 && status < 300) {
                HttpEntity entity = response.getEntity();
                return entity != null ? EntityUtils.toString(entity) : null;
            } else {
                throw new ClientProtocolException("Unexpected response status: " + status);
            }
        };
        String responseBody = httpclient.execute(request, responseHandler);
        System.out.println("----------------------------------------");
        System.out.println(responseBody);
    } finally {
        httpclient.close();
    }
}

更详细HttpClient 学习

教程参考：https://www.yiibai.com/httpclient/httpclient-overview.html （本文学习笔记）

Api参考：http://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/

github代码：https://github.com/YoCiyy/HttpClientDemo