我想通过我的 android 应用程序通过 java servlet 访问本地主机上的 mysql 数据库。我能够通过 java 类访问数据库，但是在我的 android 活动中尝试相同的代码时，它不起作用。下面是我的 java servlet 的代码，我通过它成功访问了我的数据库的 java 类和不起作用的 android 代码。在我的 LogCat 日志中，我正在获取所有日志，直到 BufferedReader 类。另外请告诉我我可以在 Android 中使用哪个小部件来显示响应字符串。我现在知道我的响应字符串将包含 HTML 代码，但这没关系我只想知道我是否能够访问我的数据库。谢谢你。Java Servlet 代码：
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 类代码：
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
}
}
}
安卓代码：
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
}
}
}