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。