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HttpClient后台跨域

引言

跨域可以说是一个经常遇到的问题,最近在联调一个身份证识别接口,该接口由python语言编写,Java语言调用,刚开始采用了CORS(Cross-Origin Resource Sharing)跨域,在IE8上一直出现兼容性问题,固定的思维容易出现错误,自己一直想着前端Ajax跨域而忽略了后台HttpClient的跨域,最后还是用HttpClient顺利解决问题,避免了浏览器跨域带来的兼容性问题。

HttpClient VS Jsonp

之前的博客有说过Jsonp的跨域方式,jsonp的核心则是动态添加<script>标签来调用服务器提供的js脚本。相比于HttpClient,Jsonp有两个很大的缺点:

1、它只能发送get请求,如果发送post请求会造成无法解析获取不到数据的问题。

2、如果返回的数据没有经过配置相应的编码文件来处理,拿到的数据可能会是一堆乱码。

问题总是能解决,HttpClient则没那么多约束,HttpClient封装了http协议的jar包,基本的请求方法get、post、put、 delete都能实现,当然得在web.xml文件中配置相应的filter拦截器拦截请求后再设好编码,一般返回的参数都是Json字符串,而我们只需要导入Jackson或者fastJson或者别的jar包来解析这对象把他转换成你所需要的数据即可。

整合Spring

添加依赖

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<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.2</version>
</dependency>

封装方法

新建HttpClientUtil工具类

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public class HttpClientUtil {

public static String doGet(String url, Map<String, String> 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<String, String> 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<NameValuePair> 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;
}
}

单元测试

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public class HttpClientTest {

@Test
public void doGet() throws Exception {
//创建一个httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
//创建一个GET对象
HttpGet get = new HttpGet("http://www.sogou.com");
//执行请求
CloseableHttpResponse response = httpClient.execute(get);
//取响应的结果
int statusCode = response.getStatusLine().getStatusCode();
System.out.println(statusCode);
HttpEntity entity = response.getEntity();
String string = EntityUtils.toString(entity, "utf-8");
System.out.println(string);
//关闭httpclient
response.close();
httpClient.close();
}

@Test
public void doGetWithParam() throws Exception{
//创建一个httpclient对象
CloseableHttpClient httpClient = HttpClients.createDefault();
//创建一个uri对象
URIBuilder uriBuilder = new URIBuilder("http://www.sogou.com/web");
uriBuilder.addParameter("query", "花千骨");
HttpGet get = new HttpGet(uriBuilder.build());
//执行请求
CloseableHttpResponse response = httpClient.execute(get);
//取响应的结果
int statusCode = response.getStatusLine().getStatusCode();
System.out.println(statusCode);
HttpEntity entity = response.getEntity();
String string = EntityUtils.toString(entity, "utf-8");
System.out.println(string);
//关闭httpclient
response.close();
httpClient.close();
}

@Test
public void doPost() throws Exception {
CloseableHttpClient httpClient = HttpClients.createDefault();

//创建一个post对象
HttpPost post = new HttpPost("http://localhost:8082/httpclient/post.action");
//执行post请求
CloseableHttpResponse response = httpClient.execute(post);
String string = EntityUtils.toString(response.getEntity());
System.out.println(string);
response.close();
httpClient.close();

}

@Test
public void doPostWithParam() throws Exception{
CloseableHttpClient httpClient = HttpClients.createDefault();

//创建一个post对象
HttpPost post = new HttpPost("http://localhost:8082/httpclient/post.action");
//创建一个Entity。模拟一个表单
List<NameValuePair> kvList = new ArrayList<>();
kvList.add(new BasicNameValuePair("username", "张三"));
kvList.add(new BasicNameValuePair("password", "123"));

//包装成一个Entity对象
StringEntity entity = new UrlEncodedFormEntity(kvList, "utf-8");
//设置请求的内容
post.setEntity(entity);

//执行post请求
CloseableHttpResponse response = httpClient.execute(post);
String string = EntityUtils.toString(response.getEntity());
System.out.println(string);
response.close();
httpClient.close();
}
}

项目实例

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/**
* 订单处理Service
* <p>Title: OrderServiceImpl</p>
* <p>Description: </p>
* @version 1.0
*/
@Service
public class OrderServiceImpl implements OrderService {

@Value("${ORDER_BASE_URL}")
private String ORDER_BASE_URL;
@Value("${ORDER_CREATE_URL}")
private String ORDER_CREATE_URL;

@Override
public String createOrder(Order order) {
//调用order的服务提交订单。
String json = HttpClientUtil.doPostJson(ORDER_BASE_URL + ORDER_CREATE_URL, JsonUtils.objectToJson(order));
//把json转换成taotaoResult
TaotaoResult taotaoResult = TaotaoResult.format(json);
if (taotaoResult.getStatus() == 200) {
Object orderId = taotaoResult.getData();
return orderId.toString();
}
return "";
}
}

总结

HttpClient与Jsonp能够轻易的解决跨域问题,从而得到自己想要的数据(来自不同IP,协议,端口),唯一的不同点是,HttpClient是在后台Java代码中进行跨域访问,而Jsonp是在前台js中进行跨域访问。跨域还有一级跨域,二级跨域,更多内容值得研究。

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