android客户端通过json连接servlet服务端
开发一个基于android的app作为一个客户端，servlet作为服务端实现简单的注册与登陆功能。通过json来传递数据，进行验证和插入。由于对json的具体规范化没做过多了解，且处于学习阶段，难免会有一些错误，尽请谅解。
本文采用的工具有tomcat ,eclipse,android studio, mysql,jdk1.8;
jar包有json-simple-1.1.1.jar,mysql-connectior-java-5.1.20-bin.jar
1.先用mysql建立一个简单的数据库文件;
mysql->create databases test;->use test;->
CREATE TABLE `admin` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`UserName` varchar(20) DEFAULT NULL,
`PassWord` varchar(20) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8;
记住数据库的字符集设置为utf8;
数据库到这里就创建完了。
2.设置服务端程序，先在eclipse中创建 Dynamic Web Project项目
(配置tomcat服务器 和jdk不写在本文中)
下图为工程文件示例：
DBConnectionHandler.java文件是用来连接数据库的文件，以下为参考代码：
package org.DBConnection;
import java.sql.*;
import java.util.logging.Level;
import java.util.logging.Logger;
public class DBConnectionHandler {
Connection con = null;
public static Connection getConnection() {
Connection con = null;
try {
Class.forName("com.mysql.jdbc.Driver");//Mysql Connection
} catch (ClassNotFoundException ex) {
Logger.getLogger(DBConnectionHandler.class.getName()).log(Level.SEVERE, null, ex);
}
try {
// con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "123456");//mysql database
String url="jdbc:mysql://localhost:3306/test?user=root&password=123456&characterEncoding=utf-8&useUnicode=true";
con=DriverManager.getConnection(url);
} catch (SQLException ex) {
Logger.getLogger(DBConnectionHandler.class.getName()).log(Level.SEVERE, null, ex);
}
return con;
}
}需要注意的是这一句：
String url="jdbc:mysql://localhost:3306/test?user=root&password=123456&characterEncoding=utf-8&useUnicode=true";
是连接Mysql的文件，其中user后面的是mysql的账号，password后面的是Mysql的密码。在后面的是传递的字符集设置为UTF-8格式，防止乱码。
LoginServlet.java文件是Servlet文件，用doget来得到客户端传进来的数据在与sql语句在数据库中进行操纵，得到一个结果，返回给客户端。
package org.servlet;
import org.DBConnection.DBConnectionHandler;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.sql.*;
import java.util.Enumeration;
import org.json.simple.JSONObject;
public class LoginServlet extends HttpServlet {
//
/**
* Handles the HTTP GET method.
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// response.setContentType("text/html;charset=UTF-8");
JSONObject json = new JSONObject();
//ObjectOutputStream out = new ObjectOutputStream(response.getOutputStream());
Enumeration paramNames = request.getParameterNames();
String params[] = new String[2];
int i = 0;
while (paramNames.hasMoreElements()) {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
String paramName = (String) paramNames.nextElement();
// System.out.println(paramName);
String[] paramValues= request.getParameterValues(paramName);
paramValues[0] = new String( paramValues[0].getBytes("iso-8859-1"),"UTF-8");
params[i] = paramValues[0];
//System.out.println(params[i]);
i++;
}
String sql = "SELECT UserName, PassWord FROM admin where UserName=? and PassWord=?";
Connection con = DBConnectionHandler.getConnection();
try {
PreparedStatement ps = con.prepareStatement(sql);
ps.setString(1, params[0]);
ps.setString(2, params[1]);
ResultSet rs = ps.executeQuery();
if (rs.next()) {
json.put("info", "success");
} else {
json.put("info", "fail");
}
} catch (Exception e) {
e.printStackTrace();
}
//System.out.println(json);
response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
response.getWriter().write(json.toString());
}
/**
* Handles the HTTP POST method.
* @param request servlet request
* @param response servlet response
* @throws ServletException if a servlet-specific error occurs
* @throws IOException if an I/O error occurs
*/
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
} 可以在url中测试数据。后面会提及。
RegisterServlet.java 文件内容：
package org.servlet;
import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.Enumeration;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.DBConnection.DBConnectionHandler;
import org.json.simple.JSONObject;
/**
* Servlet implementation class RegisterServlet
*/
@WebServlet("/RegisterServlet")
public class RegisterServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public RegisterServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
// response.getWriter().append("Served at:
// ").append(request.getContextPath());
JSONObject json = new JSONObject();
// ObjectOutputStream out = new
// ObjectOutputStream(response.getOutputStream());
Enumeration paramNames = request.getParameterNames();
String params[] = new String[2];
int i = 0;
while (paramNames.hasMoreElements()) {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
String paramName = (String) paramNames.nextElement();
String[] paramValues = request.getParameterValues(paramName);
paramValues[0] = new String( paramValues[0].getBytes("iso-8859-1"),"UTF-8");
params[i] = paramValues[0];
i++;
}
Connection conn = DBConnectionHandler.getConnection();
String sql = "insert into admin(UserName,PassWord) values(?,?)";
String sql2 = "select * from admin where UserName=?";
try {
response.setContentType("text/html; charset=utf-8");
PreparedStatement ps = conn.prepareStatement(sql2);
ps.setString(1, params[0]);
ResultSet rs = ps.executeQuery();
if (!rs.next()) {
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, params[0]);
pstmt.setString(2, params[1]);
int row = pstmt.executeUpdate();
if (row >= 1)
json.put("info", "success");
else
json.put("info", "fail");
} else
json.put("info", "fail");
} catch (Exception e) {
e.printStackTrace();
}
response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
response.getWriter().write(json.toString());
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
* response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
Web.xml配置文件：(此文件在WebContent->Web_INF文件夹下)
test1
index.html
index.htm
index.jsp
default.html
default.htm
default.jsp
LoginServlet
LoginServlet
org.servlet.LoginServlet
LoginServlet
/login.do
RegisterServlet
RegisterServlet
org.servlet.RegisterServlet
RegisterServlet
/register.do
这里就是服务端的所有程序，可以通过url来检测传入得到的数据是否正确.
检测LoginServlet.java程序的正确情况：
提前在Mysql数据库中admin表中插入一条数据账号为admin,密码为admin.
运行服务器后，在常用浏览器中输入http://localhost:8080/test1/login.do?u=admin&p=admin
浏览器会打印出{"info","success"}。u=后面或者p=后面输入其他的值，浏览器打印出{"info","fail"}说明用户名或者密码与之匹配的有一个错误。如果要更具体点可以在代码段修改去达到自己预期的效果。
检测RegisterServlet.java程序的正确情况：
在浏览器中输入http://localhost:8080/test1/register.do?u=测试中文&p=admin
会打印出来{“info”,"success"}，在去数据库文件中查看是否有一条，用户名是测试中文，密码是admin的数据。
一般情况而言只有相同的用户名存在的情况下会打印出来{"info","fail"}的情况。这段是通过在RegisterServlet.java程序中，根据get到的UserName的值通过一条sql语句检索数据库中是否存在一条相同用户名的数据，只有不存在的情况下才进行后续的插入语句，否则会直接反馈一个失败的语句。
客户端程序：
需要提前在build.gradle配置文件
dependencies {...}
中加一句
android{ useLibrary 'org.apache.http.legacy' }
JSONParser（引用别人之前的代码参考）:
import android.util.Log;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
static InputStream iStream = null;
static JSONArray jarray = null;
//static String json = "";
// constructor
public JSONParser() {
}
// function get json from url
// by making HTTP POST or GET mehtod
public JSONObject makeHttpRequest(String url, String method,
List params) {
// Making HTTP request
try {
// check for request method
if(method == "POST"){
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}else if(method == "GET"){
// request method is GET
DefaultHttpClient httpClient = new DefaultHttpClient();
String paramString = URLEncodedUtils.format(params, "utf-8");
url += "?" + paramString;
HttpGet httpGet = new HttpGet(url);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
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();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
/////////////////////////////////
public JSONArray getJSONFromUrl(String url) {
StringBuilder builder = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse response = client.execute(httpGet);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) {
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String line;
while ((line = reader.readLine()) != null) {
builder.append(line);
}
} else {
Log.e("==>", "Failed to download file");
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
// Parse String to JSON object
try {
jarray = new JSONArray( builder.toString());
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON Object
return jarray;
}
public JSONObject makeHttpRequest2(String url) {
// Making HTTP request
try {
// check for request method
//if(method == "POST"){
// request method is POST
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
// httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
// }else if(method == "GET"){
// // request method is GET
// DefaultHttpClient httpClient = new DefaultHttpClient();
// //String paramString = URLEncodedUtils.format(params, "utf-8");
// url += "?" + paramString;
// HttpGet httpGet = new HttpGet(url);
//
// HttpResponse httpResponse = httpClient.execute(httpGet);
// HttpEntity httpEntity = httpResponse.getEntity();
// is = httpEntity.getContent();
// }
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
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();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
acitivity.xml文件
登陆的客户端代码文件：
package com.example.xyf.myapplication;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends Activity {
EditText uname, password;
Button submit;
// Creating JSON Parser object
private String user;
JSONParser jParser = new JSONParser();
JSONObject json;
private static String url_login = "http://192.168.191.1:8080/test1/login.do";
//JSONArray incoming_msg = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewsById();
submit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// execute method invokes doInBackground() where we open a Http URL connection using the given Servlet URL
//and get output response from InputStream and return it.
new Login().execute();
}
});
}
private void findViewsById() {
uname = (EditText) findViewById(R.id.txtUser);
password = (EditText) findViewById(R.id.txtPass);
submit = (Button) findViewById(R.id.button1);
}
private class Login extends AsyncTask{
@Override
protected String doInBackground(String... args) {
// Getting username and password from user input
String username = uname.getText().toString();
String pass = password.getText().toString();
List params = new ArrayList();
params.add(new BasicNameValuePair("u",username));
params.add(new BasicNameValuePair("p",pass));
json = jParser.makeHttpRequest(url_login, "GET", params);
String s=null;
try {
s= json.getString("info");
Log.d("Msg", json.getString("info"));
if(s.equals("success")){
user=username;
Intent login = new Intent(getApplicationContext(), Welcome.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
finish();
}
else
{
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
} 需要注意的是：
private static String url_login = "http://192.168.191.1:8080/test1/login.do"; 我是用android真机与PC构建局域网络，远程的话只需要将192.168.191.1替换掉。
注册单元代码类似，此文不写入,只需要将login.do替换成register.do
如果注册界面需要添加不止账号密码两项数据，客户端和服务端的部分代码都需要修改。
同时此文章统一的编码为utf-8.不符合这一标准会出现乱码情况，具体情况具体分析。
此文通过此代码对url传递到servlet中的数据进行处理，最后解决乱码问题：
while (paramNames.hasMoreElements()) {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
String paramName = (String) paramNames.nextElement();
// System.out.println(paramName);
String[] paramValues= request.getParameterValues(paramName);
paramValues[0] = new String( paramValues[0].getBytes("iso-8859-1"),"UTF-8");
params[i] = paramValues[0];
//System.out.println(params[i]);
i++;
}谢谢。