Java中使用外部接口

​ Java语言有多种调用外部接口的方法,最基础版为JDK支持的使用IO流和网络编程部分技术实现.Apache对Java JDK对这个功能的实现进行的封装,形成了Apache httpclient 3(org.apache.commons.httpclient)和Apache httpclient 4(org.apache.http.client).二者是一个技术,版本不一样,3版本中还以工具类的方式存在,4版本中独立为一个包.

​ 开发中常使用Apache httpclient 4实现使用外部接口的功能.

JDK方式

​ JDK中IO流以及网络部分提供了方法实现网络请求的发送.主要使用URL对象建立网络连接,设置链接的参数后获取输入流,将输入流读入本地的StringBuffer(或其他)中返回即可.

​ post请求还需要将参数(字符串)通过流发送出去,其他无二.

get请求

​ get请求将请求体写在URL后面,所以不需要额外的输入参数.

/** * GET请求 */ public static String doGet(String httpUrl) { HttpURLConnection connection = null; InputStream is = null; BufferedReader br = null; String result = null;//返回结果字符串 try { //创建远程url连接对象 URL url = new URL(httpUrl); //通过远程url连接对象打开一个连接，强转成httpURLConnection类 connection = (HttpURLConnection) url.openConnection(); //设置连接方式：get connection.setRequestMethod("GET"); //设置连接主机服务器的超时时间：15000毫秒 connection.setConnectTimeout(15000); //设置读取远程返回的数据时间：60000毫秒 connection.setReadTimeout(60000); //通过connection连接，获取输入流 is = connection.getInputStream(); //封装输入流is，并指定字符集 br = new BufferedReader(new InputStreamReader(is, "UTF-8")); //存放数据 StringBuffer sbf = new StringBuffer(); String temp = null; while ((temp = br.readLine()) != null) { sbf.append(temp); sbf.append("\r\n");//回车+换行 } result = sbf.toString(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { //关闭资源 if (null != br) { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } if (null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } connection.disconnect();//关闭远程连接 } return result; }

post请求

​ 要额外设置输出参数,并将参数通过流输出到目标的URL中.

/** * POST 请求 */ public static String doPost(String httpUrl, String param) { HttpURLConnection connection = null; InputStream is = null; OutputStream os = null; BufferedReader br = null; String result = null; try { //创建远程url连接对象 URL url = new URL(httpUrl); //通过远程url连接对象打开连接 connection = (HttpURLConnection) url.openConnection(); //设置连接请求方式 connection.setRequestMethod("POST"); //设置连接主机服务器超时时间：15000毫秒 connection.setConnectTimeout(15000); //设置读取主机服务器返回数据超时时间：60000毫秒 connection.setReadTimeout(60000); //默认值为：false，当向远程服务器传送数据/写数据时，需要设置为true connection.setDoOutput(true); //默认值为：true，当前向远程服务读取数据时，设置为true，该参数可有可无 connection.setDoInput(true); //通过连接对象获取一个输出流 os = connection.getOutputStream(); //通过输出流对象将参数写出去/传输出去,它是通过字节数组写出的 os.write(param.getBytes());//把需要传送的参数发送给远程url //通过连接对象获取一个输入流，向远程读取 is = connection.getInputStream(); //对输入流对象进行包装 br = new BufferedReader(new InputStreamReader(is, "UTF-8")); StringBuffer sbf = new StringBuffer(); String temp = null; //循环遍历一行一行读取数据 while ((temp = br.readLine()) != null) { sbf.append(temp); sbf.append("\r\n"); } result = sbf.toString(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (ProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { //关闭资源 if (null != br) { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } if (null != os) { try { os.close(); } catch (IOException e) { e.printStackTrace(); } } if (null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } //断开与远程地址url的连接 connection.disconnect(); } return result; }

Apache httpclient 3

get请求

/** * GET 请求方法 * 注：如果需要传递参数，把参数拼接在url地址后面 */ public static String doGet(String url) { //输入流 InputStream is = null; BufferedReader br = null; String result = null; //创建httpClient实例 HttpClient httpClient = new HttpClient(); //设置http连接主机服务超时时间：15000毫秒 //先获取连接管理器对象，再获取参数对象,再进行参数的赋值 httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000); # Java中使用外部接口 ​ Java语言有多种调用外部接口的方法,最基础版为JDK支持的使用IO流和网络编程部分技术实现.Apache对Java JDK对这个功能的实现进行的封装,形成了Apache httpclient 3(org.apache.commons.httpclient)和Apache httpclient 4(org.apache.http.client).二者是一个技术,版本不一样,3版本中还以工具类的方式存在,4版本中独立为一个包. ​ 开发中常使用Apache httpclient 4实现使用外部接口的功能. ## JDK方式 ​ JDK中IO流以及网络部分提供了方法实现网络请求的发送.主要使用URL对象建立网络连接,设置链接的参数后获取输入流,将输入流读入本地的StringBuffer(或其他)中返回即可. ​ post请求还需要将参数(字符串)通过流发送出去,其他无二. ### get请求 ​ get请求将请求体写在URL后面,所以不需要额外的输入参数. ```java /** * GET请求 */ public static String doGet(String httpUrl) { HttpURLConnection connection = null; InputStream is = null; BufferedReader br = null; String result = null;//返回结果字符串 try { //创建远程url连接对象 URL url = new URL(httpUrl); //通过远程url连接对象打开一个连接，强转成httpURLConnection类 connection = (HttpURLConnection) url.openConnection(); //设置连接方式：get connection.setRequestMethod("GET"); //设置连接主机服务器的超时时间：15000毫秒 connection.setConnectTimeout(15000); //设置读取远程返回的数据时间：60000毫秒 connection.setReadTimeout(60000); //通过connection连接，获取输入流 is = connection.getInputStream(); //封装输入流is，并指定字符集 br = new BufferedReader(new InputStreamReader(is, "UTF-8")); //存放数据 StringBuffer sbf = new StringBuffer(); String temp = null; while ((temp = br.readLine()) != null) { sbf.append(temp); sbf.append("\r\n");//回车+换行 } result = sbf.toString(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { //关闭资源 if (null != br) { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } if (null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } connection.disconnect();//关闭远程连接 } return result; }

post请求

​ 要额外设置输出参数,并将参数通过流输出到目标的URL中.

/** * POST 请求 */ public static String doPost(String httpUrl, String param) { HttpURLConnection connection = null; InputStream is = null; OutputStream os = null; BufferedReader br = null; String result = null; try { //创建远程url连接对象 URL url = new URL(httpUrl); //通过远程url连接对象打开连接 connection = (HttpURLConnection) url.openConnection(); //设置连接请求方式 connection.setRequestMethod("POST"); //设置连接主机服务器超时时间：15000毫秒 connection.setConnectTimeout(15000); //设置读取主机服务器返回数据超时时间：60000毫秒 connection.setReadTimeout(60000); //默认值为：false，当向远程服务器传送数据/写数据时，需要设置为true connection.setDoOutput(true); //默认值为：true，当前向远程服务读取数据时，设置为true，该参数可有可无 connection.setDoInput(true); //通过连接对象获取一个输出流 os = connection.getOutputStream(); //通过输出流对象将参数写出去/传输出去,它是通过字节数组写出的 os.write(param.getBytes());//把需要传送的参数发送给远程url //通过连接对象获取一个输入流，向远程读取 is = connection.getInputStream(); //对输入流对象进行包装 br = new BufferedReader(new InputStreamReader(is, "UTF-8")); StringBuffer sbf = new StringBuffer(); String temp = null; //循环遍历一行一行读取数据 while ((temp = br.readLine()) != null) { sbf.append(temp); sbf.append("\r\n"); } result = sbf.toString(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (ProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { //关闭资源 if (null != br) { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } if (null != os) { try { os.close(); } catch (IOException e) { e.printStackTrace(); } } if (null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } //断开与远程地址url的连接 connection.disconnect(); } return result; }

Apache httpclient 3

get请求

/** * GET 请求方法 * 注：如果需要传递参数，把参数拼接在url地址后面 */ public static String doGet(String url) { //输入流 InputStream is = null; BufferedReader br = null; String result = null; //创建httpClient实例 HttpClient httpClient = new HttpClient(); //设置http连接主机服务超时时间：15000毫秒 //先获取连接管理器对象，再获取参数对象,再进行参数的赋值 httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000); //创建一个Get方法实例对象 GetMethod getMethod = new GetMethod(url); //设置get请求超时为60000毫秒 getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000); //设置请求重试机制，默认重试次数：3次，参数设置为true，重试机制可用，false相反 getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(3, true)); try { //执行Get方法 int statusCode = httpClient.executeMethod(getMethod); //判断返回码 if(statusCode != HttpStatus.SC_OK) { //如果状态码返回的不是ok,说明失败了,打印错误信息 System.err.println("Method faild: " + getMethod.getStatusLine()); } //通过getMethod实例，获取远程的一个输入流 is = getMethod.getResponseBodyAsStream(); //包装输入流 br = new BufferedReader(new InputStreamReader(is, "UTF-8")); StringBuffer sbf = new StringBuffer(); //读取封装的输入流 String temp = null; while ((temp = br.readLine()) != null) { sbf.append(temp).append("\r\n"); } result = sbf.toString(); } catch (HttpException e) { System.err.println("Fatal protocol violation: " + e.getMessage()); e.printStackTrace(); } catch (IOException e) { System.err.println("Fatal transport error: " + e.getMessage()); e.printStackTrace(); } finally { //关闭资源 if(null != br) { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } if(null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } //释放连接 getMethod.releaseConnection(); } return result; }

post请求

/** * POST 请求方法 */ public static String doPost(String url, Map<String,Object> paramMap) throws UnsupportedEncodingException { //获取输入流 InputStream is = null; BufferedReader br = null; String result = null; //创建httpClient实例对象 HttpClient httpClient = new HttpClient(); //设置httpClient连接主机服务器超时时间：15000毫秒 httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000); //创建post请求方法实例对象 PostMethod postMethod = new PostMethod(url); //设置post请求超时时间 postMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000); NameValuePair[] nvp = null; //判断参数map集合paramMap是否为空 if(null != paramMap && paramMap.size() > 0) {//不为空 //创建键值参数对象数组，大小为参数的个数 nvp = new NameValuePair[paramMap.size()]; //循环遍历参数集合map Set<Entry<String, Object>> entrySet = paramMap.entrySet(); //获取迭代器 Iterator<Entry<String, Object>> iterator = entrySet.iterator(); int index = 0; while(iterator.hasNext()) { Entry<String, Object> mapEntry = iterator.next(); //从mapEntry中获取key和value创建键值对象存放到数组中 nvp[index] = new NameValuePair(mapEntry.getKey(), new String(mapEntry.getValue().toString().getBytes("UTF-8"),"UTF-8")); index++; } } //判断nvp数组是否为空 if(null != nvp && nvp.length > 0) { //将参数存放到requestBody对象中 postMethod.setRequestBody(nvp); } try { //执行POST方法 int statusCode = httpClient.executeMethod(postMethod); //判断是否成功 if(statusCode != HttpStatus.SC_OK) { System.err.println("Method faild: " + postMethod.getStatusLine()); } //获取远程返回的数据 is = postMethod.getResponseBodyAsStream(); //封装输入流 br = new BufferedReader(new InputStreamReader(is, "UTF-8")); StringBuffer sbf = new StringBuffer(); String temp = null; while ((temp = br.readLine()) != null) { sbf.append(temp).append("\r\n"); } result = sbf.toString(); } catch (HttpException e) { System.err.println("Fatal protocol violation: " + e.getMessage()); e.printStackTrace(); } catch (IOException e) { System.err.println("Fatal transport error: " + e.getMessage()); e.printStackTrace(); } finally { //关闭资源 if(null != br) { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } if(null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } //释放连接 postMethod.releaseConnection(); } return result; }

Apache httpclient 4

get请求

/** * Get 请求方法 */ public static String doGet(String url) { CloseableHttpClient httpClient = null; CloseableHttpResponse response = null; String result = ""; try { //通过址默认配置创建一个httpClient实例 httpClient = HttpClients.createDefault(); //创建httpGet远程连接实例 HttpGet httpGet = new HttpGet(url); //设置配置请求参数 RequestConfig requestConfig = RequestConfig.custom() .setConnectTimeout(35000)//连接主机服务超时时间 .setConnectionRequestTimeout(35000)//请求超时时间 .setSocketTimeout(60000)//数据读取超时时间 .build(); //为httpGet实例设置配置 httpGet.setConfig(requestConfig); //执行get请求得到返回对象 response = httpClient.execute(httpGet); //通过返回对象获取返回数据 HttpEntity entity = response.getEntity(); //通过EntityUtils中的toString方法将结果转换为字符串 result = EntityUtils.toString(entity); } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { //关闭资源 if(null != response) { try { response.close(); } catch (IOException e) { e.printStackTrace(); } } if(null != httpClient) { try { httpClient.close(); } catch (IOException e) { e.printStackTrace(); } } } return result; }

post请求

​ 这里默认使用UTF-8编码,如需更改传入参数设置即可.

public static String doPost(String url, Map<String,Object> paramMap) { CloseableHttpClient httpClient = null; CloseableHttpResponse response = null; String result = ""; try { //创建httpClient实例 httpClient = HttpClients.createDefault(); //创建httpPost远程连接实例 HttpPost httpPost = new HttpPost(url); //配置请求参数实例 RequestConfig requestConfig = RequestConfig.custom() .setConnectTimeout(35000)//设置连接主机服务超时时间 .setConnectionRequestTimeout(35000)//设置连接请求超时时间 .setSocketTimeout(60000)//设置读取数据连接超时时间 .build(); //为httpPost实例设置配置 httpPost.setConfig(requestConfig); //封装post请求参数 if(null != paramMap && paramMap.size() > 0) { List<NameValuePair> nvps = new ArrayList<NameValuePair>(); //通过map集成entrySet方法获取entity Set<Entry<String, Object>> entrySet = paramMap.entrySet(); //循环遍历，获取迭代器 Iterator<Entry<String, Object>> iterator = entrySet.iterator(); while (iterator.hasNext()) { Entry<String, Object> mapEntry = iterator.next(); nvps.add(new BasicNameValuePair(mapEntry.getKey(), mapEntry.getValue().toString())); } //为httpPost设置封装好的请求参数 httpPost.setEntity(new UrlEncodedFormEntity(nvps, "UTF-8")); } //执行post请求得到返回对象 response = httpClient.execute(httpPost); //通过返回对象获取数据 HttpEntity entity = response.getEntity(); //将返回的数据转换为字符串 result = EntityUtils.toString(entity); } catch (Exception e) { e.printStackTrace(); } finally { //关闭资源 if(null != response) { try { response.close(); } catch (IOException e) { e.printStackTrace(); } } if(null != httpClient) { try { httpClient.close(); } catch (IOException e) { e.printStackTrace(); } } } return result; } //创建一个Get方法实例对象 GetMethod getMethod = new GetMethod(url); //设置get请求超时为60000毫秒 getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000); //设置请求重试机制，默认重试次数：3次，参数设置为true，重试机制可用，false相反 getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler(3, true)); try { //执行Get方法 int statusCode = httpClient.executeMethod(getMethod); //判断返回码 if(statusCode != HttpStatus.SC_OK) { //如果状态码返回的不是ok,说明失败了,打印错误信息 System.err.println("Method faild: " + getMethod.getStatusLine()); } //通过getMethod实例，获取远程的一个输入流 is = getMethod.getResponseBodyAsStream(); //包装输入流 br = new BufferedReader(new InputStreamReader(is, "UTF-8")); StringBuffer sbf = new StringBuffer(); //读取封装的输入流 String temp = null; while ((temp = br.readLine()) != null) { sbf.append(temp).append("\r\n"); } result = sbf.toString(); } catch (HttpException e) { System.err.println("Fatal protocol violation: " + e.getMessage()); e.printStackTrace(); } catch (IOException e) { System.err.println("Fatal transport error: " + e.getMessage()); e.printStackTrace(); } finally { //关闭资源 if(null != br) { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } if(null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } //释放连接 getMethod.releaseConnection(); } return result;

}

### post请求 ```java /** * POST 请求方法 */ public static String doPost(String url, Map<String,Object> paramMap) throws UnsupportedEncodingException { //获取输入流 InputStream is = null; BufferedReader br = null; String result = null; //创建httpClient实例对象 HttpClient httpClient = new HttpClient(); //设置httpClient连接主机服务器超时时间：15000毫秒 httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(15000); //创建post请求方法实例对象 PostMethod postMethod = new PostMethod(url); //设置post请求超时时间 postMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 60000); NameValuePair[] nvp = null; //判断参数map集合paramMap是否为空 if(null != paramMap && paramMap.size() > 0) {//不为空 //创建键值参数对象数组，大小为参数的个数 nvp = new NameValuePair[paramMap.size()]; //循环遍历参数集合map Set<Entry<String, Object>> entrySet = paramMap.entrySet(); //获取迭代器 Iterator<Entry<String, Object>> iterator = entrySet.iterator(); int index = 0; while(iterator.hasNext()) { Entry<String, Object> mapEntry = iterator.next(); //从mapEntry中获取key和value创建键值对象存放到数组中 nvp[index] = new NameValuePair(mapEntry.getKey(), new String(mapEntry.getValue().toString().getBytes("UTF-8"),"UTF-8")); index++; } } //判断nvp数组是否为空 if(null != nvp && nvp.length > 0) { //将参数存放到requestBody对象中 postMethod.setRequestBody(nvp); } try { //执行POST方法 int statusCode = httpClient.executeMethod(postMethod); //判断是否成功 if(statusCode != HttpStatus.SC_OK) { System.err.println("Method faild: " + postMethod.getStatusLine()); } //获取远程返回的数据 is = postMethod.getResponseBodyAsStream(); //封装输入流 br = new BufferedReader(new InputStreamReader(is, "UTF-8")); StringBuffer sbf = new StringBuffer(); String temp = null; while ((temp = br.readLine()) != null) { sbf.append(temp).append("\r\n"); } result = sbf.toString(); } catch (HttpException e) { System.err.println("Fatal protocol violation: " + e.getMessage()); e.printStackTrace(); } catch (IOException e) { System.err.println("Fatal transport error: " + e.getMessage()); e.printStackTrace(); } finally { //关闭资源 if(null != br) { try { br.close(); } catch (IOException e) { e.printStackTrace(); } } if(null != is) { try { is.close(); } catch (IOException e) { e.printStackTrace(); } } //释放连接 postMethod.releaseConnection(); } return result; }

Apache httpclient 4

get请求

/** * Get 请求方法 */ public static String doGet(String url) { CloseableHttpClient httpClient = null; CloseableHttpResponse response = null; String result = ""; try { //通过址默认配置创建一个httpClient实例 httpClient = HttpClients.createDefault(); //创建httpGet远程连接实例 HttpGet httpGet = new HttpGet(url); //设置配置请求参数 RequestConfig requestConfig = RequestConfig.custom() .setConnectTimeout(35000)//连接主机服务超时时间 .setConnectionRequestTimeout(35000)//请求超时时间 .setSocketTimeout(60000)//数据读取超时时间 .build(); //为httpGet实例设置配置 httpGet.setConfig(requestConfig); //执行get请求得到返回对象 response = httpClient.execute(httpGet); //通过返回对象获取返回数据 HttpEntity entity = response.getEntity(); //通过EntityUtils中的toString方法将结果转换为字符串 result = EntityUtils.toString(entity); } catch (ClientProtocolException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { //关闭资源 if(null != response) { try { response.close(); } catch (IOException e) { e.printStackTrace(); } } if(null != httpClient) { try { httpClient.close(); } catch (IOException e) { e.printStackTrace(); } } } return result; }

post请求

​ 这里默认使用UTF-8编码,如需更改传入参数设置即可.

public static String doPost(String url, Map<String,Object> paramMap) { CloseableHttpClient httpClient = null; CloseableHttpResponse response = null; String result = ""; try { //创建httpClient实例 httpClient = HttpClients.createDefault(); //创建httpPost远程连接实例 HttpPost httpPost = new HttpPost(url); //配置请求参数实例 RequestConfig requestConfig = RequestConfig.custom() .setConnectTimeout(35000)//设置连接主机服务超时时间 .setConnectionRequestTimeout(35000)//设置连接请求超时时间 .setSocketTimeout(60000)//设置读取数据连接超时时间 .build(); //为httpPost实例设置配置 httpPost.setConfig(requestConfig); //封装post请求参数 if(null != paramMap && paramMap.size() > 0) { List<NameValuePair> nvps = new ArrayList<NameValuePair>(); //通过map集成entrySet方法获取entity Set<Entry<String, Object>> entrySet = paramMap.entrySet(); //循环遍历，获取迭代器 Iterator<Entry<String, Object>> iterator = entrySet.iterator(); while (iterator.hasNext()) { Entry<String, Object> mapEntry = iterator.next(); nvps.add(new BasicNameValuePair(mapEntry.getKey(), mapEntry.getValue().toString())); } //为httpPost设置封装好的请求参数 httpPost.setEntity(new UrlEncodedFormEntity(nvps, "UTF-8")); } //执行post请求得到返回对象 response = httpClient.execute(httpPost); //通过返回对象获取数据 HttpEntity entity = response.getEntity(); //将返回的数据转换为字符串 result = EntityUtils.toString(entity); } catch (Exception e) { e.printStackTrace(); } finally { //关闭资源 if(null != response) { try { response.close(); } catch (IOException e) { e.printStackTrace(); } } if(null != httpClient) { try { httpClient.close(); } catch (IOException e) { e.printStackTrace(); } } } return result; }