文件操作，联网操作，服务器的创建，mysql数据库操作

第一部分:文件操作

1、首先需要添加权限

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

2、获取内存卡状态并看是否可用：Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)

3、获取目录  File sdfile = Environment.getExternalStorageDirectory();

4、然后文件的读写操作和普通的在Java中操作一样

第二部分：联网操作

1、联网无论是socket还是url都要把它放到子线程中去跑；

2、添加权限 <uses-permission android:name="android.permission.INTERNET" />

3、根据网址，创建URL，然后开启连接，设置连接属性，连接，关闭连接。

下面以一个发送post请求为例贴个代码：

public static String[] getAllDrugname() {
        URL url;
        HttpURLConnection connection;
        try {
            url = new URL(IP + "Drug");//这里是网址
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestProperty("accept", "*/*");
            connection.setDoInput(true);
            connection.setDoOutput(true);
            PrintWriter writer = new PrintWriter(connection.getOutputStream());
            writer.write("type=getAllDrugName");
            writer.flush();
            connection.connect();
            if (connection.getResponseCode() == 200) {
                InputStreamReader in = new InputStreamReader(
                        connection.getInputStream(), "UTF-8");
                StringBuilder str = new StringBuilder();
                int len;
                char[] cbuf = new char[1024];
                while ((len = in.read(cbuf, 0, cbuf.length)) != -1) {
                    str.append(new String(cbuf, 0, len));
                }
                return (str.toString()).split("[|]");
            }
        } catch (MalformedURLException e) {
            return new String[] { "Error:" + e.getMessage() };
        } catch (IOException e) {
            return new String[] { "Error" + e.getMessage() };
        }
        return null;
    }

第三部分：服务器的创建：

1、创建dynamic web project，并为之选定服务器，我用的是tomcat，数据库用的是mysql；

2、复制两个jar包到【工程目录】\\webcontent\\web-inf\\lib下面，jar包分别是mysql-connector-java-5.1.7-bin.jar（用于数据库连接）和servlet-api.jar（服务器）；

3、然后是写服务器：这里贴代码：

package Service;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.LinkedList;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import FileOperation.SaveAndReadImage;
import MySql.MySqlHelper;

public class DrugService extends HttpServlet {
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter writer = response.getWriter();
        String str = request.getParameter("type");
        System.out.println("type=" + str);
        switch (str) {
        case "getDrugMessageByName":
            String name = request.getParameter("name");
            name = new String(name.getBytes("ISO-8859-1"), "UTF-8");
            String context = getDrugMessageByName(name);
            writer.write(context);
            System.out.println("getDrugMessageByName completed");
            break;
        case "getAllDrugName":
            LinkedList<String> names = getAllDrugName();
            StringBuffer resultName = new StringBuffer();
            boolean first = true;
            for (String ele : names) {
                if (first) {
                    resultName.append(ele);
                    first = false;
                } else {
                    resultName.append("|" + ele);
                }
            }
            writer.write(resultName.toString());
            System.out.println("getAllDrugNames completed");
            break;60         default:
            writer.write("没有找到合适的匹配");
        }
        writer.flush();
        writer.close();
        System.out.println("exitService");
    }
    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doGet(req, resp);
    }86 }

4、部署服务器：这一步很关键，决定了我们的服务器是否可以被正常访问到。新建文件：[工程目录]\WebContent\WEB-INF\web.xml，内容：

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
    <servlet>
        <servlet-name>DrugService</servlet-name> 这里是给我们的服务器起个名字，任意取
        <servlet-class>Service.DrugService</servlet-class>这里要指明我们的class
    </servlet>
    <servlet-mapping>
        <servlet-name>DrugService</servlet-name>这个名字一定要和上面的名字一样
        <url-pattern>/Drug</url-pattern>这个是url后面要加的东西
    </servlet-mapping>
</web-app>

 

第四部分：数据库操作：

数据库操作主要是个流程，经清楚流程其他没什么，这里就直接贴代码了;

package MySql;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.LinkedList;

public class MySqlHelper {
    private static Connection connection;
    private static java.sql.Statement statement;
    static{
        try {
            Class.forName("com.mysql.jdbc.Driver");//加载驱动
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        Connection connection = null;
        try {
            connection = DriverManager.getConnection(
                    "jdbc:mysql://[IP]:[port]/[database]", "[name]", "[password]");//建立连接,port一般为3306
            statement=connection.createStatement();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }//-----------以下为一些数据库的增删查改等操作--------------------
    public static String[] getDrug(int id){
        StringBuffer sql=new StringBuffer("select `name`,`context` "
                + "from drug where `id`=");
        sql.append("'"+id+"'");
        ResultSet resultSet=null;
        try {
            resultSet = statement.executeQuery(sql.toString());
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            int count=resultSet.getMetaData().getColumnCount();
            System.out.println(count);
            while(resultSet.next()){
                return new String[]{resultSet.getString(1),resultSet.getString(2)};
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }57     public static LinkedList<String> getAllDrugName(){
        LinkedList<String> names=new LinkedList<String>();
        String sql=new String("select `name` from `drug`");
        ResultSet result=null;
        try {
            result = statement.executeQuery(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            while(result.next()){
                names.add(result.getString(1).trim());
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return names;
    }
    public static String getDrugMessageByName(String name){
        String sql=new String("select `context` from `drug` "
                + "where `name` like '%"+name+"%'");
        ResultSet result=null;
        try {
            result = statement.executeQuery(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        try {
            if(result.next())
                return result.getString(1);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }
}