使用Httpclient 完美解决服务端跨域问题

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）：

1. <!-- httpclient -->
2. <dependency>
3. <groupId>org.apache.httpcomponents</groupId>
4. <artifactId>httpclient</artifactId>
5. </dependency>

<!-- httpclient -->
<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：

核心代码展示：

(portal项目)contentcontroller.java

1. @Controller
2. public class ContentController {
3. @Autowired
4. private ContentService contentService;
5. //getdata
6. @RequestMapping("/content/{cid}")
7. @ResponseBody
8. public TaotaoResult getConentList(@PathVariable Long cid){
9. try {
10. List<TbContent> list=contentService.getContentList(cid);
11. return TaotaoResult.ok(list);
12. } catch (Exception e) {
13. e.printStackTrace();
14. return TaotaoResult.build(500, ExceptionUtil.getStackTrace(e));
15. }
16. }
17. }

@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

1. package com.taotao.common.utils;
2. import java.io.IOException;
3. import java.net.URI;
4. import java.util.ArrayList;
5. import java.util.List;
6. import java.util.Map;
7. import org.apache.http.NameValuePair;
8. import org.apache.http.client.entity.UrlEncodedFormEntity;
9. import org.apache.http.client.methods.CloseableHttpResponse;
10. import org.apache.http.client.methods.HttpGet;
11. import org.apache.http.client.methods.HttpPost;
12. import org.apache.http.client.utils.URIBuilder;
13. import org.apache.http.entity.ContentType;
14. import org.apache.http.entity.StringEntity;
15. import org.apache.http.impl.client.CloseableHttpClient;
16. import org.apache.http.impl.client.HttpClients;
17. import org.apache.http.message.BasicNameValuePair;
18. import org.apache.http.util.EntityUtils;
19. public class HttpClientUtil {
20. public static String doGet(String url, Map<String, String> param) {
21. // 创建Httpclient对象
22. CloseableHttpClient httpclient = HttpClients.createDefault();
23. String resultString = "";
24. CloseableHttpResponse response = null;
25. try {
26. // 创建uri
27. URIBuilder builder = new URIBuilder(url);
28. if (param != null) {
29. for (String key : param.keySet()) {
30. builder.addParameter(key, param.get(key));
31. }
32. }
33. URI uri = builder.build();
34. // 创建http GET请求
35. HttpGet httpGet = new HttpGet(uri);
36. // 执行请求
37. response = httpclient.execute(httpGet);
38. // 判断返回状态是否为200
39. if (response.getStatusLine().getStatusCode() == 200) {
40. resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
41. }
42. } catch (Exception e) {
43. e.printStackTrace();
44. } finally {
45. try {
46. if (response != null) {
47. response.close();
48. }
49. httpclient.close();
50. } catch (IOException e) {
51. e.printStackTrace();
52. }
53. }
54. return resultString;
55. }
56. public static String doGet(String url) {
57. return doGet(url, null);
58. }
59. public static String doPost(String url, Map<String, String> param) {
60. // 创建Httpclient对象
61. CloseableHttpClient httpClient = HttpClients.createDefault();
62. CloseableHttpResponse response = null;
63. String resultString = "";
64. try {
65. // 创建Http Post请求
66. HttpPost httpPost = new HttpPost(url);
67. // 创建参数列表
68. if (param != null) {
69. List<NameValuePair> paramList = new ArrayList<>();
70. for (String key : param.keySet()) {
71. paramList.add(new BasicNameValuePair(key, param.get(key)));
72. }
73. // 模拟表单
74. UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
75. httpPost.setEntity(entity);
76. }
77. // 执行http请求
78. response = httpClient.execute(httpPost);
79. resultString = EntityUtils.toString(response.getEntity(), "utf-8");
80. } catch (Exception e) {
81. e.printStackTrace();
82. } finally {
83. try {
84. response.close();
85. } catch (IOException e) {
86. // TODO Auto-generated catch block
87. e.printStackTrace();
88. }
89. }
90. return resultString;
91. }
92. public static String doPost(String url) {
93. return doPost(url, null);
94. }
95. public static String doPostJson(String url, String json) {
96. // 创建Httpclient对象
97. CloseableHttpClient httpClient = HttpClients.createDefault();
98. CloseableHttpResponse response = null;
99. String resultString = "";
100. try {
101. // 创建Http Post请求
102. HttpPost httpPost = new HttpPost(url);
103. // 创建请求内容
104. StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
105. httpPost.setEntity(entity);
106. // 执行http请求
107. response = httpClient.execute(httpPost);
108. resultString = EntityUtils.toString(response.getEntity(), "utf-8");
109. } catch (Exception e) {
110. e.printStackTrace();
111. } finally {
112. try {
113. response.close();
114. } catch (IOException e) {
115. // TODO Auto-generated catch block
116. e.printStackTrace();
117. }
118. }
119. return resultString;
120. }
121. }

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

1. @Service
2. public class ContentServiceImpl implements ContentService {
3. //service 写活，读配置文件
4. @Value("${REST_BASE_URL}")
5. private String REST_BASE_URL;
6. @Value("${REST_CONTENT_URL}")
7. private String REST_CONTENT_URL;
8. @Value("${REST_CONTENT_AD1_CID}")
9. private String REST_CONTENT_AD1_CID;
10. @Override
11. public String getAd1List() {
12. //调用服务获得数据  跨域请求：http://localhost:8081/content/89
13. String json = HttpClientUtil.doGet(REST_BASE_URL + REST_CONTENT_URL + REST_CONTENT_AD1_CID);
14. //把json转换成java对象
15. TaotaoResult taotaoResult = TaotaoResult.formatToList(json, TbContent.class);
16. //取data属性，内容列表
17. List<TbContent> contentList = (List<TbContent>) taotaoResult.getData();
18. //把内容列表转换成AdNode列表
19. List<AdNode> resultList = new ArrayList<>();
20. for (TbContent tbContent : contentList) {
21. AdNode node = new AdNode();
22. node.setHeight(240);
23. node.setWidth(670);
24. node.setSrc(tbContent.getPic());
25. node.setHeightB(240);
26. node.setWidthB(550);
27. node.setSrcB(tbContent.getPic2());
28. node.setAlt(tbContent.getSubTitle());
29. node.setHref(tbContent.getUrl());
30. resultList.add(node);
31. }
32. //需要把resultList转换成json数据
33. String resultJson = JsonUtils.objectToJson(resultList);
34. return resultJson;
35. }
36. }

@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

1. @Autowired
2. private ContentService contentService;
3. @RequestMapping("/index")
4. public String showIndex(Model model){
5. String json=contentService.getAd1List();
6. model.addAttribute("ad1",json);
7. return "index";
8. }

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


查看网页源代码，可以看到传过来的json格式的数据。

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。