BufferedReader Class not working in Android Activity
Question
I want to access mysql database on my localhost via a java servlet through my android app. I was able to access database through a java class but when tried the same code in my android activity, it's not working. Below is the code for my java servlet, java class through which I successfully accessed my database and android code which isn't working. In my LogCat log I am getting all the logs till BufferedReader class. Also please tell me which widget can I use in Android to display the response string. I know presently my response string will contain HTML code but that doesn't matter I just want to know if I am able to access my database. Thank You. Java Servlet Code:
package org.spark.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class HelloServlet2
*/
@WebServlet("/HelloServlet2")
public class HelloServlet2 extends HttpServlet {
private static final long serialVersionUID = 1L;
public void service(HttpServletRequest request,HttpServletResponse response)throws IOException, ServletException{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<head><title>Hello World</title></head>");
out.println("<body>");
out.println("<h1>Hello World2</h1>");
// connecting to database
Connection con = null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
con =DriverManager.getConnection ("jdbc:mysql://localhost:3306", "root", "password");
stmt = con.createStatement();
rs = stmt.executeQuery("Use servlettest");
rs = stmt.executeQuery("SELECT * FROM servlet");
// displaying records
while(rs.next()){
out.print(rs.getObject(1).toString());
out.print("\t\t\t");
out.print(rs.getObject(2).toString());
out.print("<br>");
}
} catch (SQLException e) {
throw new ServletException("Servlet Could not display records.", e);
} catch (ClassNotFoundException e) {
throw new ServletException("JDBC Driver not found.", e);
} finally {
try {
if(rs != null) {
rs.close();
rs = null;
}
if(stmt != null) {
stmt.close();
stmt = null;
}
if(con != null) {
con.close();
con = null;
}
} catch (SQLException e) {}
}
out.println("</body></html>");
out.close();
}
}
Java Class Code:
package org.ProjectEuler;
import java.io.*;
import java.net.*;
public class HelloServlet {
public static void main( String [] args ) {
try {
URL url = new URL("http://localhost:8080/HelloServlet/HelloServlet2");
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
BufferedWriter out = new BufferedWriter( new OutputStreamWriter( conn.getOutputStream()));
out.write("username=javaworld\r\n");
out.flush();
out.close();
BufferedReader in = new BufferedReader( new InputStreamReader( conn.getInputStream()));
String response;
while ( (response = in.readLine()) != null ) {
System.out.println( response );
}
in.close();
}
catch ( MalformedURLException ex ) {
// a real program would need to handle this exception
}
catch ( IOException ex ) {
// a real program would need to handle this exception
}
}
}
Andriod Code:
package org.spark.mysqltest;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.util.Log;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.*;
public class MySqlTestActivity extends Activity {
EditText test;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d("checked","checked");
System.out.println("check");
Log.d("checked2","checked2");
test = (EditText) findViewById(R.id.mtv);
Log.d("checked3","checked3");
setContentView(R.layout.main);
Log.d("checked4","checked4");
try {
Log.d("checked5","checked5");
URL url = new URL("http://localhost:8080/HelloServlet/HelloServlet2");
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
Log.d("checked6","checked6");
BufferedWriter out = new BufferedWriter( new OutputStreamWriter( conn.getOutputStream()));
Log.d("checked7","checked7");
out.write("username=javaworld\r\n");
Log.d("checke","checke");
out.flush();
Log.d("check","check");
out.close();
Log.d("chec","chec");
BufferedReader in = new BufferedReader( new InputStreamReader( conn.getInputStream()));
Log.d("che","che");
String response;
while ( (response = in.readLine()) != null ) {
System.out.println( response );
// test.setText(response);
Log.d("checked8","checked8");
}
Log.d("checked9","checked9");
in.close();
}
catch ( MalformedURLException ex ) {
// a real program would need to handle this exception
}
catch ( IOException ex ) {
// a real program would need to handle this exception
}
}
}
1 answers
solution1
2 ACCPTED 2012-05-30 05:59:27
First problem: you aren't specifying an encoding when you create your InputStreamReader . That means you'll use the platform default encoding, which may not be the encoding used to create the web response. (Likewise when you're creating the request.)
Second problem: you're ignoring any exceptions:
catch ( MalformedURLException ex ) {
// a real program would need to handle this exception
}
catch ( IOException ex ) {
// a real program would need to handle this exception
}
My guess is that an exception is being thrown, but you have no idea because you've swallowed those exceptions without even logging. At the very least , add logging in here and I think you'll see what's going wrong. You should almost never have empty catch statements like this.
Do you have any reason for using the low-level API like this, by the way? Using a good high-level HTTP client library is likely to make your life a lot simpler.
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