JDBC&CRUD练习
博主今日闲来无事,把前一周学的jdbc和数据的增删改查(CRUD)练习了一遍.
代码分为dbinfo.properties(数据库的连接配置), Student.java(javaBean 用于封装对象), DBUtil.java(工具类), TestCRUD.java(测试类)四部分,下面我将一一将以罗列.
先上dbinfo.properties~
driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql:///test
name=root
password=mulin123456其中driverClass值为数据库的连接驱动,url值为需要连接的库路径,jdbc:mysql:///test == jdbc:mysql://localhost:3306/test "///"为本地连接的缩写
接下来就上Student.java代码~
package login.dao;
import java.util.Date;
public class Student {
private int id;
private String name;
private String sex;
private Date birthday;
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
@Override
public String toString() {
return "id=" + id + ", name=" + name + ", sex=" + sex + ", birthday=" + birthday;
}
}
Student.java简单易懂,我就不多做介绍了.
package database.util;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ResourceBundle;
public class DBUtil {
private static String driverClass;
private static String url;
private static String name;
private static String password;
static {
//此对象用于加载properties文件数据
ResourceBundle rb = ResourceBundle.getBundle("dbinfo");
driverClass = rb.getString("driverClass");
url = rb.getString("url");
name = rb.getString("name");
password = rb.getString("password");
try {
Class.forName(driverClass);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
/*得到连接的方法*/
public static Connection getConnection() throws Exception {
return DriverManager.getConnection(url, name, password);
}
/*关闭资源的方法*/
public static void closeAll(ResultSet rs, Connection conn, Statement stmt) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs = null; // 方便gc回收
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
stmt = null;
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
conn = null;
}
}
}
DBUtil.java里主要封装的是jdbc,将数据库的连接以及关闭方法封装起来,以便测试类的调用.
下来就轮到压轴代码出场了~
先附上数据库初始内容:
1.查
package jdbcTest;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import org.junit.Test;
import database.util.DBUtil;
import login.dao.Student;
public class TestCRUD {
@Test
public void testSelect() { // 数据查找
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
conn = DBUtil.getConnection();
String sql = "SELECT * FROM student";
stmt = conn.prepareStatement(sql); // 预编译
//执行sql语句,并返回结果
rs = stmt.executeQuery();
List list = new ArrayList<> ();
/* 加载驱动
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql:///test", "root", "mulin123456"); // /// 表本地连接
stmt = conn.createStatement();*/
while (rs.next()) {
Student student = new Student();
student.setId(rs.getInt(1)); // "id"
student.setName(rs.getString("name"));
student.setSex(rs.getString("sex"));
student.setBirthday(rs.getDate(4));
list.add(student);
}
for (Student l : list) {
System.out.println(l);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBUtil.closeAll(rs, conn, stmt);
}
} 数据查找显示:
2.增
@Test
public void testInsert() { // 数据增添
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = DBUtil.getConnection();
stmt = conn.prepareStatement("INSERT INTO student VALUES(?,?,?,?)"); // 预编译
stmt.setInt(1, 5); // 1表示第一个问号“？”
stmt.setString(2, "striner");
stmt.setString(3, "女");
stmt.setString(4, "1997-02-18");
int i = stmt.executeUpdate();
if (i > 0) {
System.out.println("INSERT SUCCESS!");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBUtil.closeAll(null, conn, stmt);
}
}增添数据测试:
数据库中内容显示:
3.改
@Test
public void testUpdate() { // 数据修改
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = DBUtil.getConnection();
stmt = conn.prepareStatement("UPDATE student SET name=?,sex=?,birthday=? WHERE id=?"); // 预编译
stmt.setString(1, "xyz");
stmt.setString(2, "女");
stmt.setString(3, "2017-1-8");
stmt.setInt(4, 1);
int i = stmt.executeUpdate();
if (i > 0) { // i > 0 表执行成功
System.out.println("UPDATE SUCCESS!");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBUtil.closeAll(null, conn, stmt);
}
}数据修改结果:
数据库内容显示:
4.删
@Test
public void testDelect() { // 数据删除
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = DBUtil.getConnection();
stmt = conn.prepareStatement("DELETE FROM student WHERE id=?"); // 预编译
stmt.setInt(1, 5);
int i = stmt.executeUpdate();
if (i > 0) { // i > 0 表执行成功
System.out.println("DELETE SUCCESS!");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
DBUtil.closeAll(null, conn, stmt);
}
}
}数据删除测试:
此时数据库内容显示如下:
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想了解git代码请移步:https://github.com/striner/javaCode/blob/master/JDBC%26CRUD%E7%BB%83%E4%B9%A0