【TaoTao】使用Httpclient 完美解决服务端跨域问题

短命女 2022-07-11 05:48 202阅读 0赞

#    项目需求： #

jsonp是从前台js的角度考虑，通过Ajax调用springMVC的接口。同一个ip、同一个网络协议、同一个端口，三者都满足就是同一个域，否则就是跨域问题了。首页广告需要一个轮播的效果，取后台数据json格式。上篇博客介绍了使用jsonp来解决跨域，现在有个新的方法来解决，那就是：ajax请求地址改为自己系统的后台地址，之后在自己的后台用HttpClient请求url。封装好的跨域请求url工具类。封装一个get一个POST即可。

两者的区别就在于，jsonp是基于客户端的跨域解决。而httpclient是基于服务端的跨域解决。

我现在有两个maven项目：

Taotao-portal（8082端口）

Taotao-rest（8081端口）

要使用httpclient需要在maven中引用（portal）：

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

rest项目中写了个后台的服务调广告的数据，在portal项目中的service层来调用rest项目中的controller层提供的服务。

# httpclient工作图解： #

![Center][]

# 核心代码展示： #

(portal项目)contentcontroller.java

@Controller
    public class ContentController {
    	@Autowired
    	private ContentService contentService;
    		
    	//getdata
    	@RequestMapping("/content/{cid}")
    	@ResponseBody
    	public TaotaoResult getConentList(@PathVariable Long cid){
    		
    		try {
    			List<TbContent> list=contentService.getContentList(cid);
    			return TaotaoResult.ok(list);
    		} catch (Exception e) {
    			e.printStackTrace();
    			return TaotaoResult.build(500, ExceptionUtil.getStackTrace(e));
    		}
    	}
    }

(portal项目)HttpClientUtil.java

package com.taotao.common.utils;
    
    import java.io.IOException;
    import java.net.URI;
    import java.util.ArrayList;
    import java.util.List;
    import java.util.Map;
    
    import org.apache.http.NameValuePair;
    import org.apache.http.client.entity.UrlEncodedFormEntity;
    import org.apache.http.client.methods.CloseableHttpResponse;
    import org.apache.http.client.methods.HttpGet;
    import org.apache.http.client.methods.HttpPost;
    import org.apache.http.client.utils.URIBuilder;
    import org.apache.http.entity.ContentType;
    import org.apache.http.entity.StringEntity;
    import org.apache.http.impl.client.CloseableHttpClient;
    import org.apache.http.impl.client.HttpClients;
    import org.apache.http.message.BasicNameValuePair;
    import org.apache.http.util.EntityUtils;
    
    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;
    	}
    }

(rest项目)contentserviceimpl.java

@Service
    public class ContentServiceImpl implements ContentService {
    
    	//service 写活，读配置文件
    	@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;
    	@Override
    	public String getAd1List() {
    		//调用服务获得数据  跨域请求：http://localhost:8081/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<TbContent> contentList = (List<TbContent>) taotaoResult.getData();
    		//把内容列表转换成AdNode列表
    		List<AdNode> 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;
    	}
    }

(rest项目)indexcontroller

@Autowired
    	private ContentService contentService;
    	
    	@RequestMapping("/index")
    	public String showIndex(Model model){
    		String json=contentService.getAd1List();
    		model.addAttribute("ad1",json);
    		return "index";
    	}

查看网页源代码，可以看到传过来的json格式的数据。

![Center 1][]

# 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Java代码中进行跨域访问，而Jsonp是在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。

[Center]: /images/20220711/81a22e4d66ff4978b91a740d5fc2e00e.png
[Center 1]: /images/20220711/ed3e6924aab8403f9b5a149724f4abf5.png