arcgis api for javascript中使用proxy.jsp

當我們使用arcgis api for javascript 查詢arcgis服務時，如果查詢的參數很長時，通過get方式送出會查詢不到結果，因為get方式送出的參數有長度限制，需要通過代理的方式使用post送出。

arcgis 提供了一種解決方案就是proxy.jsp. 

首先在項目頁面js中引入 proxy.jsp：esriConfig.defaults.io.proxyUrl=http://servername:prot/arcgis_js_api/proxy.jsp  引入代理頁面

esriConfig.defaults.io.alwaysUseProxy=true;         設定代理是否一直起作用

<%@page session="false"%>
<%@page import="java.net.*,java.io.*" %>
<%!
String[] serverUrls = {
  "http://servername:8399/arcgis/rest/services"//對什麼服務起作用，可以配置多個用","分割。
};
try {
  String reqUrl = request.getQueryString();
  boolean allowed = false;
  String token = null;
  for(String surl : serverUrls) {
    String[] stokens = surl.split("\\s*,\\s*");
    if(reqUrl.toLowerCase().contains(stokens[0].toLowerCase())) {
      allowed = true;
      if(stokens.length >= 2 && stokens[1].length() > 0)
        token = stokens[1];
      break;
    }
  }
  if(reqUrl.endsWith(".png")) allowed = true;
  if(!allowed) {
    response.setStatus(403);
    return;
  }
  if(token != null) {
    reqUrl = reqUrl + (reqUrl.indexOf("?") > -1 ? "&" : "?") + "token=" + token;
  }
  		URL url = new URL(reqUrl);
        HttpURLConnection con = (HttpURLConnection)url.openConnection();
        con.setDoOutput(true);
        con.setRequestMethod(request.getMethod());
        if(request.getContentType() != null) {
          con.setRequestProperty("Content-Type", request.getContentType());
        }
  		con.setRequestProperty("Referer", request.getHeader("Referer"));
        int clength = request.getContentLength();
        if(clength > 0) {
                con.setDoInput(true);
                InputStream istream = request.getInputStream();
                OutputStream os = con.getOutputStream();
                final int length = 5000;
          byte[] bytes = new byte[length];
          int bytesRead = 0;
          while ((bytesRead = istream.read(bytes, 0, length)) > 0) {
            os.write(bytes, 0, bytesRead);
          }
        }
  else {
    con.setRequestMethod("GET");
  }
	out.clear();
	out = pageContext.pushBody();
	OutputStream ostream = response.getOutputStream();
	response.setContentType(con.getContentType());
	InputStream in = con.getInputStream();
	final int length = 5000;
	byte[] bytes = new byte[length];
	int bytesRead = 0;
	while ((bytesRead = in.read(bytes, 0, length)) > 0) {
		ostream.write(bytes, 0, bytesRead);
	}
} catch(Exception e) {
	response.setStatus(500);
}
%>