概述
JDBC是从JAVA中连接MySQL数据库的驱动，我们可以使用编程语言来实现它，其实它的实现是固定的，只用按照这个思路和步骤就可以了。
实现分为下面四个步骤：
1.注册驱动
2.获得连接对象
3.获取statement对象
4.释放资源
在我们编程时如果需要操作数据库只需要按照这四个步骤就可以了。
我事先在Navicat for MySQL中建了一个store数据库，并且创建了一个有四个字段的学生表，如下图：
因为操作数据库无外乎增删改查这些，如果单单每一种操作都重新写代码的话，会显得冗余复杂，太LOW了，所以可以适当的对代码进行优化，具体的实现如下：
测试用得学生类如下：
package cn.edu360.entity;
public class Student {
private Integer id;
private String name;
private String gender;
private int age;
public Student() {
}
public Student(Integer id, String name, String gender, int age) {
super();
this.id = id;
this.name = name;
this.gender = gender;
this.age = age;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", gender=" + gender + ", age=" + age + "]";
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
将四个步骤中的1、2、4封装成cn.edu360.utils如下：
package cn.edu360.utils;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
/*
* JDBC四个步骤
*/
public class JDBCUtils {
private static String driverName = "com.mysql.jdbc.Driver";
private static String jdbc_url = "jdbc:mysql://localhost:3306/store";
private static String username = "root";
private static String password = "12580";
// 1.注册驱动，只需要注册一次即可（在静态代码中执行一次即可）
static {
try {
Class.forName(driverName);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
// 2.获得连接对象，以后需要多次获得
public static Connection getConnection() {
try {
return DriverManager.getConnection(jdbc_url, username, password);
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
// 3.获取statement对象，需要反复执行，不需要定义这个方法了
// 4.释放资源，需要反复执行的(使用方法的重载来定义两个不同参数列表的释放方法)
public static void release(Statement stmt, Connection connection) {
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
stmt = null;
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
connection = null;
}
}
public static void release(ResultSet rs, Statement stmt, Connection connection) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
rs = null;
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
stmt = null;
}
if (connection != null) {
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
connection = null;
}
}
}
增删改查封装成cn.edu360.dao如下：
package cn.edu360.dao;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import cn.edu360.entity.Student;
import cn.edu360.utils.JDBCUtils;
public class StudentDao {
/**
* 添加数据到MySQL中
*
* @param student
*/
public void save(Student student) {
// 获得connection
Connection connection = JDBCUtils.getConnection();
PreparedStatement prepareStatement = null;
// 创建Statement对象
// 定义一个sql
String sql = "INSERT INTO student VALUES (?, ?, ?, ?)";
try {
prepareStatement = connection.prepareStatement(sql);
prepareStatement.setInt(1, student.getId());
prepareStatement.setString(2, student.getName());
prepareStatement.setString(3, student.getGender());
prepareStatement.setInt(4, student.getAge());
// 执行sql语句
prepareStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
// 释放资源
JDBCUtils.release(prepareStatement, connection);
}
/**
* 根据ID号删除数据
*
* @param id
*/
public void deleteById(Integer id) {
// 获得connection
Connection connection = JDBCUtils.getConnection();
PreparedStatement prepareStatement = null;
// 创建Statement对象
// 定义一个sql
String sql = "DELETE FROM student WHERE id = ?";
try {
prepareStatement = connection.prepareStatement(sql);
prepareStatement.setInt(1, id);
// 执行sql语句
prepareStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
// 释放资源
JDBCUtils.release(prepareStatement, connection);
}
/**
* 更新学生信息
*
* @param student
*/
public void update(Student student) {
// 获得connection
Connection connection = JDBCUtils.getConnection();
PreparedStatement prepareStatement = null;
// 创建Statement对象
// 定义一个sql
String sql = "UPDATE student SET name = ? , gender = ? , age = ? WHERE id = ?";
try {
prepareStatement = connection.prepareStatement(sql);
prepareStatement.setString(1, student.getName());
prepareStatement.setString(2, student.getGender());
prepareStatement.setInt(3, student.getAge());
prepareStatement.setInt(4, student.getId());
// 执行sql语句
prepareStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}
// 释放资源
JDBCUtils.release(prepareStatement, connection);
}
/**
* 根据ID号查找学生信息
*
* @param id
* @return
*/
public Student getById(Integer id) {
Student s = null;
// 获得connection
Connection connection = JDBCUtils.getConnection();
PreparedStatement prepareStatement = null;
ResultSet rs =null;
// 创建Statement对象
// 定义一个sql
String sql = "SELECT * FROM student WHERE id = ?";
try {
prepareStatement = connection.prepareStatement(sql);
prepareStatement.setInt(1,id);
// 执行sql语句
rs = prepareStatement.executeQuery();
// 从rs中得到数据
rs.next();
Integer sid = rs.getInt(1);
String name = rs.getString(2);
String gender = rs.getString(3);
int age = rs.getInt(4);
s = new Student();
s.setId(sid);
s.setName(name);
s.setGender(gender);
s.setAge(age);
} catch (SQLException e) {
e.printStackTrace();
}
// 释放资源
JDBCUtils.release(rs,prepareStatement, connection);
return s;
}
/**
* 查找所有学生信息
*
* @return
*/
public List<Student> findAll() {
ArrayList<Student> list = new ArrayList<Student>();
// 获得connection
Connection connection = JDBCUtils.getConnection();
PreparedStatement prepareStatement = null;
ResultSet rs = null;
// 创建Statement对象
// 定义一个sql
String sql = "SELECT * FROM student";
try {
prepareStatement = connection.prepareStatement(sql);
// 执行sql语句
rs = prepareStatement.executeQuery();
while (rs.next()) {
// 从rs中得到数据
Integer sid = rs.getInt(1);
String name = rs.getString(2);
String gender = rs.getString(3);
int age = rs.getInt(4);
Student s = new Student();
s.setId(sid);
s.setName(name);
s.setGender(gender);
s.setAge(age);
list.add(s);
}
} catch (SQLException e) {
e.printStackTrace();
}
// 释放资源
JDBCUtils.release(rs,prepareStatement, connection);
return list;
}
}
测试代码如下：
package cn.edu360.test;
import java.util.List;
import org.junit.Test;
import cn.edu360.dao.StudentDao;
import cn.edu360.entity.Student;
public class TestDao {
@Test
public void testSave() {
StudentDao dao = new StudentDao();
Student s = new Student(11, "tom", "f", 20);
dao.save(s);
}
@Test
public void testDelete() {
StudentDao dao = new StudentDao();
dao.deleteById(11);
}
@Test
public void testUpdate() {
StudentDao dao = new StudentDao();
Student s = new Student(1, "zhaozhoa", "m", 18);
dao.update(s);
}
@Test
public void testGetById() {
StudentDao dao = new StudentDao();
Student s = dao.getById(2);
System.out.println(s);
}
@Test
public void testFindAll() {
StudentDao dao = new StudentDao();
List<Student> list = dao.findAll();
for (Student s : list) {
System.out.println(s);
}
}
}
最后
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