import java.sql.*;
import java.sql.Connection;
import java.sql.PreparedStatement;
import bean.Student;
public class test1 {
//函数功能:链接数据库,返回Connection实例
private static Connection getConn() {
String driver = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/demo";//mysql版本较高,报SSL警告
//String url = "jdbc:mysql://127.0.0.1:3306/demo?useUnicode=true&characterEncoding=utf-8&useSSL=false";
String username = "root";
String password = "123456";
Connection conn = null;
/**(1)
* 要获取数据库联机必须有一下几个动作:
* (1)注册Driver操作对象
* (2)取得Connection操作对象
* (3)关闭Connection操作对象
*
* 其中(1)使用JDBC时,要求加载.class文档的方式有4种
* (1)使用Class.getName();
* (2)自行建立Driver接口操作类的实例(registerDriver)
* (3)启动JVM时,指定jdbc.drivers属性
* (4)设定JAR中/services/java.drivers属性
*/
/**(2)
* Connection操作对象:
* Connection接口的操作对象时数据库联机代表对象,要取得Connection操作对象,可以通过DriverManager的getConnection();
* Connection conn = DriverManager.getConnection(jdbcURL, username, password);
*
* jdbcURL:定义了链接数据库时的协议,子协议,数据源识别()
* mysql为例
* 子协议名称:mysql
* 数据源识别主要 标出数据库地址,端口号, 名称, 用户, 密码
*
*/
/**
* (3)
* SQLException: 数据库操作过程中发生错误的代表对象,
* SQLExecption是受检异常(Checked Exception)必须TryCatchFinally
* 在异常时关闭相关资源
*
*/
//驱动注册:DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//实际上很少自己撰写上述代码进行动作,只通过forName()就可以进行动态加载驱动程序类
try {
Class.forName(driver); //classLoader,加载对应驱动//(1)
conn = (Connection) DriverManager.getConnection(url, username, password);//进行链接(2)
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {//这异常要经常处理!(3)
e.printStackTrace();
}
return conn;//返回Connection对象
}
/**
* 以下是数据的增删改查操作,很好理解
* 主要就是Statement类,主要就是用来执行sql语句
* PreparedStatement是预先编译好的sql语句,一般用这个,比较方便
* 当参数会变动的部分,先指定"?"占位,如下(4)
* 然后再调 setString() / setInt()
*
* 执行语句: statement.executeUpdate();
* 还有一个clearParameters()方法,用来清除设置的参数,之后就可以再次使用这个实例
*/
/**
* 新增
* @param student
* @return
*/
private static int insert(Student student) {
Connection conn = getConn();
int i = 0;
String sql = "insert into student (Name,Sex,Age) values(?,?,?)";//(4)
//创建PreparedStatment实例
PreparedStatement pstmt;
try {
//设置sql语句
pstmt = (PreparedStatement) conn.prepareStatement(sql);
pstmt.setString(1, student.getName());
pstmt.setString(2, student.getSex());
pstmt.setString(3, student.getAge());
//执行
i = pstmt.executeUpdate();//这玩意应该是返回affected row(s) 受影响列
pstmt.close();//关
conn.close();//关
} catch (SQLException e) {//处理异常
e.printStackTrace();
}
return i;
}
/**
* 修改
* @param student
* @return
*/
private static int update(Student student) {
Connection conn = getConn();
int i = 0;
String sql = "update student set Age='" + student.getAge() + "' where Name='" + student.getName() + "'";
PreparedStatement pstmt;
try {
pstmt = (PreparedStatement) conn.prepareStatement(sql);
i = pstmt.executeUpdate();
System.out.println("resutl: " + i);
pstmt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
return i;
}
/**
* 查询
* @return
*/
private static Integer getAll() {
Connection conn = getConn();
String sql = "select * from student";
PreparedStatement pstmt;
try {
pstmt = (PreparedStatement)conn.prepareStatement(sql);
ResultSet rs = pstmt.executeQuery();
int col = rs.getMetaData().getColumnCount();
System.out.println("+----------------------------+");
while (rs.next()) {
for (int i = 1; i <= col; i++) {
System.out.print(rs.getString(i) + "\t");
if ((i == 2) && (rs.getString(i).length() < 8)) {
System.out.print("\t");
}
}
System.out.println("");
}
System.out.println("+----------------------------+");
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
/**
* 删除
* @param name
* @return
*/
private static int delete(String name) {
Connection conn = getConn();
int i = 0;
String sql = "delete from student where Name='" + name + "'";
PreparedStatement pstmt;
try {
pstmt = (PreparedStatement) conn.prepareStatement(sql);
i = pstmt.executeUpdate();
System.out.println("resutl: " + i);
pstmt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
return i;
}
public static void main(String args[]) {
/*est1.insert(new Student("A", "Male", "1"));
test1.insert(new Student("B", "Male", "2"));
test1.insert(new Student("C", "Male", "3"));*/
//test1.getAll();
//test1.update(new Student("B", "", "7"));
//test1.delete("C");
test1.getAll();
}
}