Question

JDBC 如何取出数据库里的数据~菜鸟求救！！！！！

public class Main extends JFrame{
static Main m = new Main();

TextField tf = new TextField(10);
TextArea ta = new TextArea(10,15);
public static void main(String[] args) {
m.launchFrame();
}
public void launchFrame(){
private class ConfirmButton implements ActionListener{
private static final int INFORMATION_MESSAGE = 0;
public void actionPerformed(ActionEvent e) {
if(tf.getText().equals(""))
{
JOptionPane.showMessageDialog(null, "请输入问题！","Warning",INFORMATION_MESSAGE);
return;
}
else
{
String str = connect.getDeptName();
ta.setText(str);
}
}
}
}
}
------------------------------------------------------------------------------
public class Connect{

Main m = new Main();
private String deptName;

public String getDeptName(){
String deptNo1 = m.tf.getText();

ResultSet rs = null;
Statement stmt = null;
Connection conn = null;
PreparedStatement ps = null;
try{
Class.forName("oracle.jdbc.driver.OracleDriver");
conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl","scott","tiger");
stmt = conn.createStatement();

ps = conn.prepareStatement("select DNAME from dept where deptno = ?");
ps.setString(1,deptNo1);
rs = ps.executeQuery();

while(rs.next()){
deptName = rs.getString(1);
}
}catch(ClassNotFoundException e){
e.printStackTrace();
}catch(SQLException e){
e.printStackTrace();
}finally{
try{
if(rs!=null){
rs.close();
rs = null;
}
if(ps!=null){
ps.close();
ps = null;
}
if(conn!=null){
conn.close();
conn = null;
}
}catch(SQLException e){
e.printStackTrace();
}
}
return deptName;//返回对应的DANME;
}
}

两个类的关键代码就是这些，为什么还是读不出数据来，我想实现的就是tf中输入10,然后把数据库里10对应的A输入到ta中........如何实现...
DEPTNO DNAME
10 A

Answer 1

注意：你需要在项目中引入“ojdbc6.jar”才可以在java中访问Oracle。

修改后的Java程序：

import java.awt.FlowLayout;

import java.awt.TextArea;

import java.awt.TextField;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JOptionPane;

class Main extends JFrame implements ActionListener {

TextField tf;

TextArea ta;

JButton btn;

    

public Main(){

super();

tf = new TextField(10);

ta = new TextArea(10,15);

btn = new JButton("确定");

this.setLayout(new FlowLayout());

this.add(tf);

this.add(btn);

this.add(ta);

btn.addActionListener(this);

this.setSize(200, 200);

this.setVisible(true);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

public static void main(String[] args) {

        new Main();

    }

@Override

public void actionPerformed(ActionEvent e) {

if(tf.getText().equals("")) {

JOptionPane.showMessageDialog(null, "请输入问题！","Warning", 0);

return;

}

else {

String str = Connect.getDeptName(tf.getText());

ta.setText(str);

}

}

}

class Connect{

public static String getDeptName(String deptNo1){

ResultSet rs = null;

Statement stmt = null;

Connection conn = null;

PreparedStatement ps = null;

String deptName = null;

try {

Class.forName("oracle.jdbc.driver.OracleDriver");

conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl","scott","tiger");

stmt = conn.createStatement();

ps = conn.prepareStatement("select DNAME from dept where deptno = ?");

ps.setString(1,deptNo1);

rs = ps.executeQuery();

if(rs.next()){

deptName = rs.getString(1);

}

}

catch(ClassNotFoundException e){

 e.printStackTrace();

}

catch(SQLException e){

e.printStackTrace();

}

finally{

try{

if(rs!=null){

rs.close();

rs = null;

}

if(ps!=null){

ps.close();

ps = null;

}

if(conn!=null){

conn.close();

conn = null;

}

}

catch(SQLException e){

e.printStackTrace();

}

}

return deptName;//返回对应的DANME;

}

}

运行测试：

追问

我另建了一个表mytbs 插入了一条数据
QUESTION ANSWER
天气 小雪
语句改为
ps = conn.prepareStatement("select ANSWER from mytbs where QUESTION = ?");
为什么就输出不了了，不解...

追答

你插入数据后，要加
commit;
这样才能将当前会话中的更改影响到数据库。

追问

可是我已经在sqlplus中能看到插入的数据了呐.另外....commit怎么加....

追答

insert into ...;
commit;

回答完毕!

追问

哥，赶紧让我给你分吧 - - ! 还是不行....
stmt = conn.createStatement();
stmt.addBatch("insert into mytbs values('abc','def')");//插入语句
stmt.executeBatch();
stmt.close();
conn.commit();
ps = conn.prepareStatement("select ANSWER from mytbs where QUESTION = ?");
ps.setString(1,deptNo1);
rs = ps.executeQuery();

追答

请不要再追问了，在百度Hi里说吧!
以下代码是可以了，我测试了。

try {
Class.forName("oracle.jdbc.driver.OracleDriver");
conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl","scott","tiger");

stmt = conn.createStatement();
stmt.addBatch("insert into mytbs values('abc','def')");//插入语句
stmt.executeBatch();
stmt.close();
conn.commit();

ps = conn.prepareStatement("select ANSWER from mytbs where QUESTION = ?");
ps.setString(1, deptNo1);
rs = ps.executeQuery();

if(rs.next()){
deptName = rs.getString(1);
}
}