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String  
try{  
        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());  
}