跨域问题解决方案(HttpClient安全跨域 & jsonp跨域)

观审美2 2017-03-25

展开全文

1 错误场景

今天要把项目部署到外网的时候,出现了这样的问题, 我把两个项目放到自己本机的tomcat下, 进行代码调试, 运行

都没有问题的, 一旦把我需要调用接口的项目B放到其他的服务器上, 就会报错, 无法通过Ajax调用springMVC的接口,

这是什么原因呢?

当我使用json ajax post请求传递数据的时候在web端出错:XMLHttpRequest cannot loadhttp://ip:8082/security/auth/outside.do. Origin http://ip:8080 is not allowed by Access-Control-Allow-Origin.

2 初识jsonp

经过在网上查找, 网上大多数说是跨域问题. 解决跨域问题据说是jsonp, 百度了一篇文章, 不管三七二十一就一下

子把ajax传递的数据类型dataType 改成为jsonp, 并使用get方式, 单纯的认为, json和jsonp没啥区别, 运行, 报错, 如

下图所示:

没有了上述的 is not allowed ....的错误, 变成了只剩下500的错误, 说明jsonp起了些作用, 我的bug的问题就是在于网上说的"跨域" 。而究竟什么是跨域呢？

3 什么是跨域？什么是不跨域？

上没有过多的去测试，一句话：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。而为什么开发者最初不直接定为一切可跨域的呢？默认的为什么都是不可跨域呢？这就涉及到了同源策

略，为了系统的安全，由Netscape提出一个著名的安全策略。现在所有支持JavaScript的浏览器都会使用这个策略。

所谓同源是，域名，协议，端口相同。当我们在浏览器中打开百度和谷歌两个网站时，百度浏览器在执行一个脚本的

时候会检查这个脚本属于哪个页面的，即检查是否同源，只有和百度同源的脚本才会被执行，如果没有同源策略，那

随便的向百度中注入一个js脚本，弹个恶意广告，通过js窃取信息，这就很不安全了。

4 跨域问题如何解决？jsonp为什么能解决跨域问题？和json有什么区别？

关于解决跨域问题，有多种解决方案，解决方案如下。

4.1 方案一

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

代码如下所示。

[java] view plain copy

print?

<span style="font-size:18px;">@SuppressWarnings("all")
public final class UrlUtil {
private static HttpClient httpClient = new HttpClient();
/**
* @Title: getDataFromURL
* @Description: 根据URL跨域获取输出结果，支持http
* @param strURL
* 要访问的URL地址
* @param param
* 参数
* @return 结果字符串
* @throws Exception
*/
public static String getDataFromURL(String strURL, Map<String, String> param) throws Exception {
URL url = new URL(strURL);
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
final StringBuilder sb = new StringBuilder(param.size() << 4); // 4次方
final Set<String> keys = param.keySet();
for (final String key : keys) {
final String value = param.get(key);
sb.append(key); // 不能包含特殊字符
sb.append('=');
sb.append(value);
sb.append('&');
}
// 将最后的 '&' 去掉
sb.deleteCharAt(sb.length() - 1);
writer.write(sb.toString());
writer.flush();
writer.close();
InputStreamReader reder = new InputStreamReader(conn.getInputStream(), "utf-8");
BufferedReader breader = new BufferedReader(reder);
// BufferedWriter w = new BufferedWriter(new FileWriter("d:/1.txt"));
String content = null;
String result = null;
while ((content = breader.readLine()) != null) {
result += content;
}
return result;
}
/**
* @Title: postMethod
* @Description: 根据URL跨域获取输出结果，支持https
* @param url
* 要访问的URL地址(http://www.?)
* @param urlParm
* 参数(id=1212&pwd=2332)
* @return 结果字符串
*/
public static String postMethod(String url, String urlParm) {
if (null == url || "".equals(url)) {
// url = "http://www.baidu.com";
return null;
}
PostMethod post = new PostMethod(url); // new UTF8PostMethod(url);
if (null != urlParm && !"".equals(urlParm)) {
String[] arr = urlParm.split("&");
NameValuePair[] data = new NameValuePair[arr.length];
for (int i = 0; i < arr.length; i++) {
String name = arr[i].substring(0, arr[i].lastIndexOf("="));
String value = arr[i].substring(arr[i].lastIndexOf("=") + 1);
data[i] = new NameValuePair(name, value);
}
post.setRequestBody(data);
}
int statusCode = 0;
String pageContent = "";
try {
statusCode = httpClient.executeMethod(post);
if (statusCode == HttpStatus.SC_OK || statusCode == HttpStatus.SC_MOVED_TEMPORARILY) {
pageContent = post.getResponseBodyAsString();
return pageContent;
}
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
post.releaseConnection();
}
return null;
}
public static String doPost(String url, String json) throws Exception {
PostMethod postMethod = new PostMethod(url);
StringRequestEntity requestEntity = new StringRequestEntity(json, "application/json", "UTF-8");
postMethod.setRequestEntity(requestEntity);
/* 发送请求，并获取响应对象 */
int statusCode = httpClient.executeMethod(postMethod);
String result = null;
if (statusCode == HttpStatus.SC_OK) {
result = postMethod.getResponseBodyAsString();
} else {
System.out.println("Method failed: " + postMethod.getStatusLine());
}
return result;
}
public static String post(String url, Map<String, String> params) {
DefaultHttpClient httpclient = new DefaultHttpClient();
String body = null;
HttpPost post = postForm(url, params);
body = invoke(httpclient, post);
httpclient.getConnectionManager().shutdown();
return body;
}
private static HttpPost postForm(String url, Map<String, String> params) {
HttpPost httpost = new HttpPost(url);
List<BasicNameValuePair> nvps = new ArrayList<BasicNameValuePair>();
Set<String> keySet = params.keySet();
for (String key : keySet) {
BasicNameValuePair basicNameValuePair = new BasicNameValuePair(key, params.get(key));
nvps.add(basicNameValuePair);
}
try {
httpost.setEntity(new UrlEncodedFormEntity(nvps, HTTP.UTF_8));
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
return httpost;
}
private static String invoke(DefaultHttpClient httpclient, HttpUriRequest httpost) {
HttpResponse response = sendRequest(httpclient, httpost);
String body = paseResponse(response);
return body;
}
private static HttpResponse sendRequest(DefaultHttpClient httpclient, HttpUriRequest httpost) {
HttpResponse response = null;
try {
response = httpclient.execute(httpost);
} catch (Exception e) {
e.printStackTrace();
}
return response;
}
private static String paseResponse(HttpResponse response) {
HttpEntity entity = response.getEntity();
String body = null;
try {
body = EntityUtils.toString(entity);
} catch (Exception e) {
e.printStackTrace();
}
return body;
}
public static void main(String[] args) throws Exception {
String url = "http://ip:8082/security/auth/outside.do";
Map<String, String> map = new HashMap<String, String>();
map.put("loginName", "root");
map.put("code", "vms2.0");
String msg = post(url, map);
JSONArray jary = JsonUtil.Json2JSONArray(msg);
for (int i = 0; i < jary.length(); i++) {
JSONObject obj = jary.getJSONObject(i);
System.out.println(obj);
// System.out.print(obj.getString("classid"));
// System.out.print("\t"+obj.getString("classname"));
// System.out.println("\t"+obj.getString("sonclass"));
}
// System.out.println(jary);
}
}</span>