JDBC的四个步骤和代码实现

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：

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;
	}

}

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;
		}
	}

}

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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