安卓+servlet+MySql 查询+插入（汉字乱码解决）
16lz
2021-01-22
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：
1 package com.linfeng;
2 import java.io.ByteArrayInputStream;
3 import java.io.DataInputStream;
4 import java.io.IOException;
5 import java.io.OutputStream;
6 import java.io.UnsupportedEncodingException;
7 import java.net.HttpURLConnection;
8 import java.net.URL;
9 import java.net.URLEncoder;
10 import java.util.ArrayList;
11 import java.util.List;
12
13 import org.apache.http.HttpClientConnection;
14 import org.apache.http.HttpEntity;
15 import org.apache.http.HttpResponse;
16 import org.apache.http.NameValuePair;
17 import org.apache.http.client.ClientProtocolException;
18 import org.apache.http.client.entity.UrlEncodedFormEntity;
19 import org.apache.http.client.methods.HttpPost;
20 import org.apache.http.client.methods.HttpUriRequest;
21 import org.apache.http.client.utils.URLEncodedUtils;
22 import org.apache.http.impl.client.DefaultHttpClient;
23 import org.apache.http.message.BasicNameValuePair;
24 import org.apache.http.protocol.HTTP;
25 import org.apache.http.util.EntityUtils;
26
27 import android.R.string;
28 import android.app.Activity;
29 import android.app.ProgressDialog;
30 import android.os.AsyncTask;
31 import android.os.Bundle;
32 import android.util.Log;
33 import android.view.View;
34 import android.view.View.OnClickListener;
35 import android.widget.Button;
36 import android.widget.EditText;
37 import android.widget.TextView;
38 public class MainActivity extends Activity {
39 // private static final int REQUEST_CODE = 2;
40 HttpPost httpRequest = new HttpPost(UriAPI.HTTPCustomer);
41 EditText et_name;
42 EditText et_xuenian;
43 EditText et_xueqi;
44 TextView show_login;
45 Button btn_login;
46 Button btn_cancle;
47 ProgressDialog progressDialog;
48 /** Called when the activity is first created. */
49 @Override
50 public void onCreate(Bundle savedInstanceState) {
51 super.onCreate(savedInstanceState);
52 setContentView(R.layout.main);
53 // 初始化登陆界面
54 btn_login = (Button) findViewById(R.id.btn_login);
55 btn_cancle = (Button) findViewById(R.id.btn_cancle);
56 et_name = (EditText) findViewById(R.id.et_name);
57 et_xuenian = (EditText) findViewById(R.id.xuenian);
58 et_xueqi = (EditText) findViewById(R.id.xueqi);
59 show_login = (TextView) findViewById(R.id.show_login);
60 progressDialog = new ProgressDialog(this);
61 btn_login.setOnClickListener(new OnClickListener() {
62 @SuppressWarnings("unchecked")
63 @Override
64 public void onClick(View v) {
65 // 通过AsyncTask类提交数据 异步显示
66 new AT().execute("20133079", "2016");
67 }
68 });
69 }
70 public class UriAPI {
71 /** 定义一个Uri **/
72 public static final String HTTPCustomer = "http://10.0.2.2:8080/JSONDemo/servlet/Insertdomo";
73 }
74 @SuppressWarnings("rawtypes")
75 class AT extends AsyncTask {
76 String result = "success";
77 private HttpURLConnection conn;
78 @Override
79 protected void onPreExecute() {
80 // 加载progressDialog
81 progressDialog.show();
82 }
83 @Override
84 protected Object doInBackground(Object... params_obj) {
85 CharSequence username ="20133078";
86 CharSequence suggest = "铁大jjk";
87
88 suggest = et_name.getText();
89
90 suggest=suggest.toString();
91
92
93 try {
94 username = new String(((String) username).getBytes("UTF-8"),"iso8859-1");
95 suggest = new String(((String) suggest).getBytes("UTF-8"),"iso8859-1");
96 } catch (Exception e1) {
97 // TODO Auto-generated catch block
98 e1.printStackTrace();
99 }
100
101
102 if (!username.equals("") && !suggest.equals("")) {
103 // 请求数据
104 HttpPost httpRequest = new HttpPost(UriAPI.HTTPCustomer);
105 // 创建参数
106 List<NameValuePair> params = new ArrayList<NameValuePair>();
107 params.add(new BasicNameValuePair("username", username
108 .toString()));
109 params.add(new BasicNameValuePair("suggest", suggest.toString()
110 ));
111 System.out.println(params);
112 // params.add(new BasicNameValuePair("flag","0"));
113 try {
114 // 对提交数据进行编码
115 httpRequest.setEntity(new UrlEncodedFormEntity(params,
116 HTTP.ISO_8859_1));
117 System.out.println(params);
118 System.out.println(httpRequest);
119 HttpResponse httpResponse = new DefaultHttpClient()
120 .execute(httpRequest);
121 // 获取响应服务器的数据
122 if (httpResponse.getStatusLine().getStatusCode() == 200) {
123 // 利用字节数组流和包装的绑定数据
124 byte[] data = new byte[2048];
125 // 先把从服务端来的数据转化成字节数组
126 data = EntityUtils
127 .toByteArray((HttpEntity) httpResponse
128 .getEntity());
129 // 再创建字节数组输入流对象
130 ByteArrayInputStream bais = new ByteArrayInputStream(
131 data);
132 // 绑定字节流和数据包装流
133 DataInputStream dis = new DataInputStream(bais);
134 // 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：
135 result = new String(dis.readUTF());
136 Log.i("服务器返回信息:", result);
137 }
138 } catch (ClientProtocolException e) {
139 e.printStackTrace();
140 } catch (UnsupportedEncodingException e) {
141 e.printStackTrace();
142 } catch (IOException e) {
143 e.printStackTrace();
144 }
145 }
146 return result;
147 }
148 @Override
149 protected void onPostExecute(Object result) {
150 // 获得服务器返回信息成功后
151 System.out.print(result);
152 show_login.setText(result.toString()); //显示 success
153 // 取消进度条
154 progressDialog.cancel();
155
156 if(result.toString()=="success")
157 {
158 setContentView(R.layout.classlistselect);
159 }
160 }
161 }
162 }
服务端Servlet代码：
1、连接数据库db：
1 package db;
2
3 import java.sql.Connection;
4 import java.sql.DriverManager;
5 import java.sql.PreparedStatement;
6 import java.sql.ResultSet;
7 import java.sql.SQLException;
8
9 import exception.DbException;
10 public class DbUtils {
11 private final static String DRIVER="com.mysql.jdbc.Driver";
12 private final static String URL="jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8";
13 private final static String NAME="root";
14 private final static String PWD="123456";
15 private static Connection conn=null;
16 public static Connection getConenction(){
17 try {
18 Class.forName(DRIVER);
19 conn=DriverManager.getConnection(URL, NAME, PWD);
20 } catch (ClassNotFoundException e) {
21 throw new DbException("");
22 } catch (SQLException e) {
23 throw new DbException("");
24 }catch (Exception e){
25 throw new DbException(e);
26
27 }
28 return conn;
29 }
30 public static void freeDb(Connection conn,PreparedStatement pmst,ResultSet rs){
31 try {
32 if (rs!=null) {
33 rs.close();
34
35 }
36 } catch (Exception e) {
37 throw new DbException("");
38 }
39 try {
40 if (pmst!=null) {
41 pmst.close();
42
43 }
44 } catch (Exception e) {
45 throw new DbException("");
46 }
47 try {
48 if (conn!=null) {
49 conn.close();
50
51 }
52 } catch (Exception e) {
53 throw new DbException("");
54 }
55
56 }
57
58 }
2、servlet代码：
1 package servlet;
2
3
4 import java.io.DataOutputStream;
5 import java.io.IOException;
6 import javax.servlet.ServletException;
7 import javax.servlet.http.HttpServlet;
8 import javax.servlet.http.HttpServletRequest;
9 import javax.servlet.http.HttpServletResponse;
10
11 import dao.Insertdom;
12 public class Insertdomo extends HttpServlet {
13 private static final long serialVersionUID = 314719472293387358L;
14
15 @Override
16 protected void doPost(HttpServletRequest req, HttpServletResponse resp)
17 throws ServletException, IOException {
18 String re="";
19 String username = req.getParameter("username");
20 String suggest = req.getParameter("suggest");
21 username = new String(username.getBytes("iso8859-1"),"UTF-8");
22 suggest = new String(suggest.getBytes("iso8859-1"),"UTF-8");
23 boolean flag = Insertdom.Add(username,suggest);
24 // try {
25 // resp.setCharacterEncoding("UTF-8");
26 // DataOutputStream output=new DataOutputStream(resp.getOutputStream());
27 // if ("20133079".equals(username) && "天上".equals(suggest)) {
28 // re = "suggest";
29 // }else{
30 // re = suggest;
31 // }
32 try {
33 resp.setCharacterEncoding("UTF-8");
34 DataOutputStream output=new DataOutputStream(resp.getOutputStream());
35 if (flag) {
36 re = "成功";
37 }else{
38 re = "失败";
39 }
40 output.writeUTF(re);
41 output.writeInt(1);
42 output.close();
43 System.out.print(re);
44 } catch (Exception e) {
45 e.printStackTrace();
46 }
47
48 }
49 }
3、插入具体实现函数：
1 package dao;
2
3 import java.io.UnsupportedEncodingException;
4 import java.sql.Connection;
5 import java.sql.PreparedStatement;
6 import java.sql.SQLException;
7
8 import db.DbUtils;
9 import exception.DbException;
10
11 public class Insertdom {
12 static Connection conn = null;
13 /**
14
15 */
16 static {
17 conn=DbUtils.getConenction();
18
19 }
20 private final static String SQL="insert into suggest(username,suggest) values (?,?)";
21 /**
22 * @throws UnsupportedEncodingException
23
24 */
25 public static boolean Add(String username,String suggest) throws UnsupportedEncodingException{
26 PreparedStatement pmst = null;
27 int rs = 0;
28 boolean flag = true;
29 try {
30 pmst = conn.prepareStatement(SQL);
31 pmst.setString(1, username);
32 pmst.setString(2, suggest);
33 rs=pmst.executeUpdate();
34 } catch (SQLException e) {
35
36 throw new DbException("查询无", e);
37 }
38 if (rs == 0) {
39 flag = false;
40 System.out.println("新增失败");
41 } else {
42 flag = true;
43 System.out.println("新增成功");
44 }
45 return flag;
46 }
47 }
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。
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