使用JDBC进行数据库连接，并对数据库进行CRUD操作

mysql数据库表
classinfo表

代码部分

DBUtil工具类

package com.zc.util;


import java.sql.*;

public class DBUtil {
    public static final String URL = "jdbc:mysql://127.0.0.1:3306/mydb";
    public static final String UNAME = "root";
    public static final String PWD = "123456";
    Connection conn;

    /**
     * 获取数据库连接
     * @return 返回数据库连接对象
     */
    public Connection getConn(){
        try {
            Class.forName("com.mysql.jdbc.Driver");
            try {
                conn = DriverManager. getConnection(URL,UNAME,PWD);
            } catch (SQLException e) {
                e.printStackTrace();
            }
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        return conn;
    }

    /**
     * 关闭数据库连接
     */
    public void close(){
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}

classinfo实体类

package com.zc.entity;

/**
 * calssInfo实体类
 */
public class ClassInfo {
    private int classId;
    private String className;

    public int getClassId() {
        return classId;
    }

    public void setClassId(int classId) {
        this.classId = classId;
    }

    public String getClassName() {
        return className;
    }

    public void setClassName(String className) {
        this.className = className;
    }

    public ClassInfo() {
        super();
    }

    public ClassInfo(int classId, String className) {
        this.classId = classId;
        this.className = className;
    }

    public ClassInfo(String className) {
        this.className = className;
    }
}

dao层接口 未实现的增删改查方法

package com.zc.dao;

import com.zc.entity.ClassInfo;

import java.util.List;

public interface ClassInfoDao {
    /**
     * 查询全部班级信息
     * @return list集合里面存的是班级信息
     */
    public List<ClassInfo> findAll();

    /**
     * 根据id查询班级信息
     * @param id 班级编号
     * @return 班级对象
     */
    public ClassInfo findById(int id);

    /**
     * 添加班级信息
     * @param c 班级对象
     * @return 数字结果
     */
    public int add(ClassInfo c);

    /**
     * 删除班级信息
     * @param id 班级编号
     * @return 数字结果
     */
    public int delete(int id);

    /**
     * 修改班级信息
     * @param c 班级对象
     * @return 数字结果
     */
    public int update(ClassInfo c);
}

daoImpl实现dao层接口

package com.zc.daoimpl;

import com.zc.dao.ClassInfoDao;
import com.zc.entity.ClassInfo;
import com.zc.util.DBUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class ClassInfoDaoImpl implements ClassInfoDao {
    @Override
    public List<ClassInfo> findAll() {
        List<ClassInfo> list = new ArrayList<ClassInfo>();
        DBUtil db = new DBUtil();
        Connection conn = db.getConn();
        String sql = "select * from classinfo";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ResultSet rs = ps.executeQuery();
            while(rs.next()){
                ClassInfo c = new ClassInfo(rs.getInt("classid"),rs.getString("classname"));
                list.add(c);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return list;
    }

    @Override
    public ClassInfo findById(int id) {
        List<ClassInfo> list = new ArrayList<ClassInfo>();
        DBUtil db = new DBUtil();
        Connection conn = db.getConn();
        String sql = "select * from classinfo where classid = ?";
        ClassInfo c = null;
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1,id);
            ResultSet rs = ps.executeQuery();
            if(rs.next()){
                c = new ClassInfo(rs.getInt("classid"),rs.getString("classname"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return c;
    }

    @Override
    public int add(ClassInfo c) {
        DBUtil db = new DBUtil();
        Connection conn = db.getConn();
        String sql = "insert into classinfo values(null,?)";
        int result = 0;
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1,c.getClassName());
            result = ps.executeUpdate();

        } catch (SQLException e) {
            e.printStackTrace();
        }
        return result;
    }

    @Override
    public int delete(int id) {
        DBUtil db = new DBUtil();
        Connection conn = db.getConn();
        String sql = "delete from classinfo where classid = ?";
        int result = 0;
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1,id);
            result = ps.executeUpdate();

        } catch (SQLException e) {
            e.printStackTrace();
        }
        return result;
    }

    @Override
    public int update(ClassInfo c) {
        DBUtil db = new DBUtil();
        Connection conn = db.getConn();
        String sql = "update classinfo set classname = ? where classid = ?";
        int result = 0;
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1,c.getClassName());
            ps.setInt(2,c.getClassId());
            result = ps.executeUpdate();

        } catch (SQLException e) {
            e.printStackTrace();
        }
        return result;
    }
}

classTest测试类

package com.zc.text;

import com.zc.dao.ClassInfoDao;
import com.zc.daoimpl.ClassInfoDaoImpl;
import com.zc.entity.ClassInfo;

import java.util.ArrayList;
import java.util.List;

public class ClassInfoTest {
    public static void main(String[] args) {
        /*ClassInfoDao cid = new ClassInfoDaoImpl();
        List<ClassInfo> list = new ArrayList<ClassInfo>();
        list = cid.findAll();
        for (ClassInfo c : list){
            System.out.println(c.getClassId()+"\t"+c.getClassName());
        }*/

        /*ClassInfoDao cid = new ClassInfoDaoImpl();
        ClassInfo c = new ClassInfo();
        c = cid.findById(1);
        System.out.println(c.getClassId()+"\t"+c.getClassName());*/

        /*ClassInfoDao cid = new ClassInfoDaoImpl();
        ClassInfo c = new ClassInfo("java班");
        int i = cid.add(c);
        if(i>0){
            System.out.println("添加成功");
        }*/

        /*ClassInfoDao cid = new ClassInfoDaoImpl();
        int i = cid.delete(4);
        if(i>0){
            System.out.println("删除成功");
        }*/

        ClassInfoDao cid = new ClassInfoDaoImpl();
        ClassInfo c = new ClassInfo(3,"java3班");
        int i = cid.update(c);
        if(i>0){
            System.out.println("修改成功");
        }


    }
}