Android连接远程数据库
Android虽然自带java.sql包，但是各数据库的JDBC Driver是否可用争议很多，不论国内网站还是国外网站，有人说能用，有人说不行，有人说虚拟机上能跑，上真手机就不行，有人说自己在手机上测试过也能跑。但不管怎么说，直接连接远程数据库被公认不是一个很好的做法，至少在安全性上非常差的，所以现在最简单也是最流行的做法是访问远程服务器前段的PHP，PHP函数完成数据库操作，把结果经过JSON编码后传回，Android端再parse出结果。
SQL数据库创建测试表people 代码如下：
CREATE TABLE `people` ( `id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY , `name` VARCHAR( 100 ) NOT NULL , `sex` BOOL NOT NULL DEFAULT '1', `birthyear` INT NOT NULL)
PHP前端文件getAllPeopleBornAfter.php代码如下,查询出生年月在year之后的人:
<?php mysql_connect("host","username","password"); mysql_select_db("PeopleData"); $q=mysql_query("SELECT * FROM people WHERE birthyear>'".$_REQUEST['year']."'"); while($e=mysql_fetch_assoc($q)) $output[]=$e; print(json_encode($output)); mysql_close();?>
Android客户端的方法略微复杂一点，代码如下:
String result = "";//首先使用NameValuePair封装将要查询的年数和关键字绑定ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();nameValuePairs.add(new BasicNameValuePair("year","1980")); //使用HttpPost封装整个SQL语句//使用HttpClient发送HttpPost对象try{ HttpClient httpclient = new DefaultHttpClient(); HttpPost httppost = new HttpPost("http://example.com/getAllPeopleBornAfter.php"); httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs)); HttpResponse response = httpclient.execute(httppost); HttpEntity entity = response.getEntity(); InputStream is = entity.getContent();}catch(Exception e){ Log.e("log_tag", "Error in http connection "+e.toString());}//将HttpEntity转化为Stringtry{ BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8); StringBuilder sb = new StringBuilder(); String line = null; while ((line = reader.readLine()) != null) { sb.append(line + "\n"); } is.close(); result=sb.toString();}catch(Exception e){ Log.e("log_tag", "Error converting result "+e.toString());} //将String通过JSONArray解析成最终结果try{ JSONArray jArray = new JSONArray(result); for(int i=0;i<jArray.length();i++){ JSONObject json_data = jArray.getJSONObject(i); Log.i("log_tag","id: "+json_data.getInt("id")+ ", name: "+json_data.getString("name")+ ", sex: "+json_data.getInt("sex")+ ", birthyear: "+json_data.getInt("birthyear") ); }}}catch(JSONException e){ Log.e("log_tag", "Error parsing data "+e.toString());}
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