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创建一个Util工具类
创建工具类为了方便后期管理,例如对数据库做出修改的时候只需要在工具类里修改一处即可!
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public final class JdbcUtils {
private static String url = "jdbc:mysql://localhost:3306/mydb";
private static String user = "root";
private static String password = "000000";
private JdbcUtils() {
}
static { //静态代码块,加载jdbc驱动一次
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
throw new ExceptionInInitializerError(e);
}
}
public static Connection getConnection() throws SQLException {
return DriverManager.getConnection(url, user, password);
}
//释放资源进行判断
public static void free(ResultSet rs, PreparedStatement ps, Connection conn) {
try {
if (rs != null)
rs.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (ps != null)
ps.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (conn != null)
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
}
创建一个测试类
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class Base {
public static void main(String[] args) throws Exception {
template("张三");
}
static void template(String name) throws SQLException, ClassNotFoundException {
Connection conn = null;
//Statement st = null;
PreparedStatement ps = null; // 比上一种解决了SQL注入的问题 安全!还快
ResultSet rs = null;
try {
// 2.建立连接
conn = JdbcUtils.getConnection();
// 3.创建语句
//st = conn.createStatement();
String sql = "select * from user where name = ?";
ps = conn.prepareStatement(sql);
ps.setString(1, name);
// 4.执行语句
//rs = st.executeQuery("select * from user");
rs = ps.executeQuery();
// 5.处理结果
while (rs.next()) {
// 参数中的1,2,3,4是指sql中的列索引
System.out.println(rs.getObject(1) + "\t" + rs.getObject(2)
);
}
} finally {
JdbcUtils.free(rs, ps, conn);
}
}
}
实现简单增删改查
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class CRUD {
public static void main(String[] args) throws SQLException {
// create();
read();
// update();
// delete();
}
static void delete() throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
// 2.建立连接
conn = JdbcUtils.getConnection();
// 3.创建语句
st = conn.createStatement();
String sql = "delete from user where id>4";
// 4.执行语句
int i = st.executeUpdate(sql);
System.out.println("i=" + i);
} finally {
JdbcUtils.free(rs, st, conn);
}
}
static void update() throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
// 2.建立连接
conn = JdbcUtils.getConnection();
// 3.创建语句
st = conn.createStatement();
String sql = "update user set money=money+10 ";
// 4.执行语句
int i = st.executeUpdate(sql);
System.out.println("i=" + i);
} finally {
JdbcUtils.free(rs, st, conn);
}
}
static void create() throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
// 2.建立连接
conn = JdbcUtils.getConnection();
// conn = JdbcUtilsSing.getInstance().getConnection();
// 3.创建语句
st = conn.createStatement();
String sql = "insert into user(name,birthday, money) values ('name1', '1987-01-01', 400) ";
// 4.执行语句
int i = st.executeUpdate(sql);
System.out.println("i=" + i);
} finally {
JdbcUtils.free(rs, st, conn);
}
}
static void read() throws SQLException {
Connection conn = null;
Statement st = null;
ResultSet rs = null;
try {
// 2.建立连接
conn = JdbcUtils.getConnection();
// 3.创建语句
st = conn.createStatement();
// 4.执行语句
rs = st.executeQuery("select id, name, money, birthday from user");
// 5.处理结果
while (rs.next()) {
System.out.println(rs.getObject("id") + "\t"
+ rs.getObject("name") + "\t"
+ rs.getObject("birthday") + "\t"
+ rs.getObject("money"));
}
} finally {
JdbcUtils.free(rs, st, conn);
}
}
}