安卓+servlet+MySql 查询+插入（汉字乱码解决）

问题：

　　安卓程序，通过servlet连接MySQL数据库，并实现查询和插入（修改，删除类似）。

其中遇到的最大的问题是：汉字乱码问题（查询条件有汉字乱码、servlet的汉字到数据乱码、安卓通过servlet方法数据库汉字乱码）

　　当所有的编码（客户端，服务端，数据库）都为UTF-8时，但是插入汉字依然为乱码。

　　1、安卓客户端中的汉字到servlet中为乱码。

　　　　当插入到数据库的汉字为乱码（而不是问号）时。

　　　　解决方法：

　　　　在安卓客户端将String中的汉字由UTF-8转码为ISO8859-1.

　　　　username = new String(((String) username).getBytes("UTF-8"),"iso8859-1");

　　　　在servlet服务端将String中的汉字由ISO8859-1转码为UTF-8.

　　　　username = new String(username.getBytes("iso8859-1"),"UTF-8");

　　　　至此，servlet中收到的汉字即为正确的汉字而不是乱码。

　　　　如果，此时插入到数据库中的汉字由乱码改成了问号，那么请看2.

　　2、servlet到数据库中为问号。

　　　　判断此种情况，可在servlet中的SQL语句直接赋值，而不是再获取。如果数据库中显示为问号时。

　　　　解决方法：

　　　　jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8

　　　　其中必须有 ?useUnicode=true&characterEncoding=utf8 而且不能有其他。

具体例子：

安卓客户端代码：

　　

 package com.linfeng;
 import java.io.ByteArrayInputStream;
 import java.io.DataInputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.io.UnsupportedEncodingException;
 import java.net.HttpURLConnection;
 import java.net.URL;
 import java.net.URLEncoder;
 import java.util.ArrayList;
 import java.util.List;

 import org.apache.http.HttpClientConnection;
 import org.apache.http.HttpEntity;
 import org.apache.http.HttpResponse;
 import org.apache.http.NameValuePair;
 import org.apache.http.client.ClientProtocolException;
 import org.apache.http.client.entity.UrlEncodedFormEntity;
 import org.apache.http.client.methods.HttpPost;
 import org.apache.http.client.methods.HttpUriRequest;
 import org.apache.http.client.utils.URLEncodedUtils;
 import org.apache.http.impl.client.DefaultHttpClient;
 import org.apache.http.message.BasicNameValuePair;
 import org.apache.http.protocol.HTTP;
 import org.apache.http.util.EntityUtils;

 import android.R.string;
 import android.app.Activity;
 import android.app.ProgressDialog;
 import android.os.AsyncTask;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.EditText;
 import android.widget.TextView;
 public class MainActivity extends Activity {
     // private static final int REQUEST_CODE = 2;
     HttpPost httpRequest = new HttpPost(UriAPI.HTTPCustomer);
     EditText et_name;
     EditText et_xuenian;
     EditText et_xueqi;
     TextView show_login;
     Button btn_login;
     Button btn_cancle;
     ProgressDialog progressDialog;
     /** Called when the activity is first created. */
     @Override
     public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.main);
         // 初始化登陆界面
         btn_login = (Button) findViewById(R.id.btn_login);
         btn_cancle = (Button) findViewById(R.id.btn_cancle);
         et_name = (EditText) findViewById(R.id.et_name);
         et_xuenian = (EditText) findViewById(R.id.xuenian);
         et_xueqi = (EditText) findViewById(R.id.xueqi);
         show_login = (TextView) findViewById(R.id.show_login);
         progressDialog = new ProgressDialog(this);
         btn_login.setOnClickListener(new OnClickListener() {
             @SuppressWarnings("unchecked")
             @Override
             public void onClick(View v) {
                 // 通过AsyncTask类提交数据 异步显示
                 new AT().execute("20133079", "2016");
             }
         });
     }
     public class UriAPI {
         /** 定义一个Uri **/
         public static final String HTTPCustomer = "http://10.0.2.2:8080/JSONDemo/servlet/Insertdomo";
     }
     @SuppressWarnings("rawtypes")
     class AT extends AsyncTask {
         String result = "success";
         private HttpURLConnection conn;
         @Override
         protected void onPreExecute() {
             // 加载progressDialog
             progressDialog.show();
         }
         @Override
         protected Object doInBackground(Object... params_obj) {
             CharSequence username ="20133078";
             CharSequence suggest = "铁大jjk";

             suggest = et_name.getText();

             suggest=suggest.toString();

             try {
                 username = new String(((String) username).getBytes("UTF-8"),"iso8859-1");
                 suggest = new String(((String) suggest).getBytes("UTF-8"),"iso8859-1");
             } catch (Exception e1) {
                 // TODO Auto-generated catch block
                 e1.printStackTrace();
             }

             if (!username.equals("") && !suggest.equals("")) {
                 // 请求数据
                 HttpPost httpRequest = new HttpPost(UriAPI.HTTPCustomer);
                 // 创建参数
                 List<NameValuePair> params = new ArrayList<NameValuePair>();
                 params.add(new BasicNameValuePair("username", username
                         .toString()));
                 params.add(new BasicNameValuePair("suggest", suggest.toString()
                         ));
                 System.out.println(params);
                 // params.add(new BasicNameValuePair("flag","0"));
                 try {
                     // 对提交数据进行编码
                     httpRequest.setEntity(new UrlEncodedFormEntity(params,
                             HTTP.ISO_8859_1));
                     System.out.println(params);
                     System.out.println(httpRequest);
                     HttpResponse httpResponse = new DefaultHttpClient()
                             .execute(httpRequest);
                     // 获取响应服务器的数据
                     if (httpResponse.getStatusLine().getStatusCode() == 200) {
                         // 利用字节数组流和包装的绑定数据
                         byte[] data = new byte[2048];
                         // 先把从服务端来的数据转化成字节数组
                         data = EntityUtils
                                 .toByteArray((HttpEntity) httpResponse
                                         .getEntity());
                         // 再创建字节数组输入流对象
                         ByteArrayInputStream bais = new ByteArrayInputStream(
                                 data);
                         // 绑定字节流和数据包装流
                         DataInputStream dis = new DataInputStream(bais);
                         // 将字节数组中的数据还原成原来的各种数据类型，代码如下：
                         result = new String(dis.readUTF());
                         Log.i("服务器返回信息:", result);
                     }
                 } catch (ClientProtocolException e) {
                     e.printStackTrace();
                 } catch (UnsupportedEncodingException e) {
                     e.printStackTrace();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
             return result;
         }
         @Override
         protected void onPostExecute(Object result) {
             // 获得服务器返回信息成功后
             System.out.print(result);
             show_login.setText(result.toString()); //显示  success
             // 取消进度条
             progressDialog.cancel();

             if(result.toString()=="success")
             {
                 setContentView(R.layout.classlistselect);
             }
         }
     }
 }

服务端Servlet代码：

　　1、连接数据库db：

 package db;

 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;

 import exception.DbException;
 public class DbUtils {
     private final static String DRIVER="com.mysql.jdbc.Driver";
     private final static String URL="jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8";
     private final static String NAME="root";
     private final static String PWD="123456";
     private static Connection conn=null;
         public static Connection getConenction(){
         try {
             Class.forName(DRIVER);
             conn=DriverManager.getConnection(URL, NAME, PWD);
         } catch (ClassNotFoundException e) {
          throw new DbException("");
         } catch (SQLException e) {
             throw new DbException("");
         }catch (Exception e){
             throw new DbException(e); 

         }
         return conn;
     }
         public static void freeDb(Connection conn,PreparedStatement pmst,ResultSet rs){
         try {
             if (rs!=null) {
                 rs.close();

             }
         } catch (Exception e) {
             throw new DbException("");
         }
         try {
             if (pmst!=null) {
                 pmst.close();

             }
         } catch (Exception e) {
             throw new DbException("");
         }
         try {
             if (conn!=null) {
                 conn.close();

             }
         } catch (Exception e) {
             throw new DbException("");
         }

     }

 }

　　2、servlet代码：

 package servlet;

 import java.io.DataOutputStream;
 import java.io.IOException;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import dao.Insertdom;
 public class Insertdomo extends HttpServlet {
     private static final long serialVersionUID = 314719472293387358L;

     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp)
             throws ServletException, IOException {
         String re="";
         String username = req.getParameter("username");
         String suggest = req.getParameter("suggest");
         username = new String(username.getBytes("iso8859-1"),"UTF-8");
         suggest = new String(suggest.getBytes("iso8859-1"),"UTF-8");
         boolean flag = Insertdom.Add(username,suggest);
 //        try {
 //            resp.setCharacterEncoding("UTF-8");
 //            DataOutputStream output=new DataOutputStream(resp.getOutputStream());
 //            if ("20133079".equals(username) && "天上".equals(suggest)) {
 //            re = "suggest";
 //        }else{
 //            re = suggest;
 //        }
         try {
             resp.setCharacterEncoding("UTF-8");
             DataOutputStream output=new DataOutputStream(resp.getOutputStream());
             if (flag) {
             re = "成功";
         }else{
             re = "失败";
         }
         output.writeUTF(re);
         output.writeInt(1);
         output.close();
         System.out.print(re);
         } catch (Exception e) {
             e.printStackTrace();
         }

     }
 }

　　3、插入具体实现函数：

 package dao;

 import java.io.UnsupportedEncodingException;
 import java.sql.Connection;
 import java.sql.PreparedStatement;
 import java.sql.SQLException;

 import db.DbUtils;
 import exception.DbException;

 public class Insertdom {
     static Connection conn = null;
     /**

      */
     static {
         conn=DbUtils.getConenction();

     }
     private final static String SQL="insert into suggest(username,suggest) values (?,?)";
     /**
      * @throws UnsupportedEncodingException 

      */
     public static boolean Add(String username,String suggest) throws UnsupportedEncodingException{
         PreparedStatement pmst = null;
         int rs = 0;
         boolean flag = true;
         try {
             pmst = conn.prepareStatement(SQL);
             pmst.setString(1, username);
             pmst.setString(2, suggest);
             rs=pmst.executeUpdate();
         } catch (SQLException e) {

             throw new DbException("查询无", e);
         }
          if (rs == 0) {
                 flag = false;
                 System.out.println("新增失败");
             } else {
                 flag = true;
                 System.out.println("新增成功");
             }
             return flag;
     }
 }

这只是安卓通过servlet访问数据库的一种方法，还有更多的方法值得我们去学习。