[大数据]简单版手写ORM框架

简单版手写ORM框架
项目结构

1.引入jar包
<dependencies> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.27</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.2.7</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency> </dependencies>

AnMyTableFieldId 注解

//标记主键使用的
//在属性名上使用
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface AnMyTableFieldId {
    String value();
}

AnMyTableFiled

//标记不同的字段名
public @interface AnMyTableFiled {
    String value();
}

AnMyTableName

//自定义注解
//只能在类上使用
@Target(ElementType.TYPE)
//运行时注解还在作用范围内
@Retention(RetentionPolicy.RUNTIME)
public @interface AnMyTableName {
    String value();
}

AccountDao

public class AccountDao  extends BaseDao<Account> {
}

Account

@AnMyTableName("account")
public class Account {
    @AnMyTableFieldId("username")
    private String username;
    @AnMyTableFiled("balance")
    private Integer balance;


    @Override
    public String toString() {
        return "Account{" +
                "username='" + username + '\'' +
                ", balance=" + balance +
                '}';
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Integer getBalance() {
        return balance;
    }

    public void setBalance(Integer balance) {
        this.balance = balance;
    }
}

DbUtil

package com.ccr.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Properties;

@SuppressWarnings("all")
public class DbUtil {
//    声明数据源对象
  private  static DataSource dataSource;

    static {
        try {
            InputStream inputStream = DbUtil.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
//          读取配置文件
            properties.load(inputStream);
//            根据配置文件中的内容为datasourcse配置
            dataSource = DruidDataSourceFactory.createDataSource(properties);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
//    获取连接池对象
    public  static Connection getConn(){
// 连接池中获取连接对象
        try {
            Connection connection = dataSource.getConnection();
            return connection;
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return null;
    }
//    关闭资源
    public static void close(ResultSet r, PreparedStatement ps, Connection c) {

        if (r != null) {
            try {
                r.close();

                if (ps != null) {
                    ps.close();
                }
                if (c != null) {
                    c.close();
                }

            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        }
    }
}

BaseDao

package com.ccr.util;


import com.ccr.annotation.AnMyTableFieldId;
import com.ccr.annotation.AnMyTableFiled;
import com.ccr.annotation.AnMyTableName;

import java.lang.reflect.Field;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

//表加数据
public class BaseDao<T> {
    public PreparedStatement ps;
    public Connection conn;
    public ResultSet rs;
    private Class<?> aClass;

    public BaseDao() {
//        当前对象的直接超类的Type
//获取子类Dao的反射类对象
        Class<? extends BaseDao> aClazz = this.getClass();
//        获取子类对象以及子类对象泛型
        ParameterizedType genericSuperclass = (ParameterizedType) aClazz.getGenericSuperclass();
//   获取子类中的泛型对象
        Type[] actualTypeArguments = genericSuperclass.getActualTypeArguments();
//       获取反射对象
        aClass = (Class<?>) actualTypeArguments[0];
//        System.out.println(aClass);

    }

    //    查询所有
    public List<T> findAll() {

//        查询的方法是以一个数组
        List<T> list = new ArrayList<T>();
        StringBuffer sql = new StringBuffer("select * from ");
//        获取表名
        String tableName = aClass.getAnnotation(AnMyTableName.class).value();
//        sql添加表名
        sql.append(tableName);

//        执行sql语句
        try {
//        连接数据库
            conn = DbUtil.getConn();
            ps = conn.prepareStatement(sql.toString());
            rs = ps.executeQuery();
//            获取到所有字段名
            while (rs.next()){
//                创建实体类对象
                Object o = aClass.newInstance();
//获取属性名
                Field[] declaredFields = aClass.getDeclaredFields();
                for (Field f: declaredFields) {
//                    设置属性课件性
                    f.setAccessible(true);
//                    循环获取到表中的属性，但是不严谨，实体类中数据可能和数据组数据不对照
//                    f.set(o,rs.getObject(f.getName()));
                    AnMyTableFieldId annotationid = f.getAnnotation(AnMyTableFieldId.class);
//
                    if (annotationid!=null){
                        f.set(o,rs.getObject(annotationid.value()));
                    }
                    AnMyTableFiled annotationname = f.getAnnotation(AnMyTableFiled.class);
                    if (annotationname!=null){
                        f.set(o,rs.getObject(annotationname.value()));
                    }else {
                        f.set(o,rs.getObject(f.getName()));
                    }
                }
                list.add((T) o);

            }

        } catch (Exception throwables) {
            throwables.printStackTrace();
        } finally {
            DbUtil.close(null, ps, conn);
        }
        return list;

    }

    //     根据id查询
    public T findById(Object id){
        StringBuffer sql = new StringBuffer("select * from ");
//        获取表名
        String tableName = aClass.getAnnotation(AnMyTableName.class).value();
        sql.append(tableName+" where ");
//        获取主键id
//        先获取所有
        Field[] declaredFields = aClass.getDeclaredFields();
        for (Field f: declaredFields){
            AnMyTableFieldId annotationid = f.getAnnotation(AnMyTableFieldId.class);
                if (annotationid!=null){
                    String valueid = annotationid.value();
//                    添加到数据中
                    sql.append(valueid+"='"+id+"'");
                    break;
                }

        }
        try {
//        连接数据库
            conn = DbUtil.getConn();
            ps = conn.prepareStatement(sql.toString());
            rs = ps.executeQuery();
            //                创建实体类对象

            Object o = aClass.newInstance();
//            获取到所有字段名
            if (rs.next()){

                for (Field f: declaredFields) {
//                    设置属性课件性
                    f.setAccessible(true);
//                    循环获取到表中的属性，但是不严谨，实体类中数据可能和数据组数据不对照
//                    f.set(o,rs.getObject(f.getName()));
                    AnMyTableFieldId annotationid = f.getAnnotation(AnMyTableFieldId.class);
//
                    if (annotationid!=null){
                        f.set(o,rs.getObject(annotationid.value()));
                    }
                    AnMyTableFiled annotationname = f.getAnnotation(AnMyTableFiled.class);
                    if (annotationname!=null){
                        f.set(o,rs.getObject(annotationname.value()));
                    }else {
                        f.set(o,rs.getObject(f.getName()));
                    }
                }
              return (T) o;


            }

        } catch (Exception throwables) {
            throwables.printStackTrace();
        }finally {
            DbUtil.close(null, ps, conn);
        }
//        System.out.println(sql);
        return null;
    }

    //添加功能所有表的添加功能。 insert into 表（） values（）
    public int insert(T t) {


        try {
//        声明一个字符串sql语句
            StringBuffer sql = new StringBuffer("insert into ");
//        通过泛型获取反射类对象
            Class<?> aClass = t.getClass();
//        通过注解得到类名
            AnMyTableName anMyTableName = aClass.getAnnotation(AnMyTableName.class);
//        获取表名
            String tableName = anMyTableName.value();
//        把获取的表名拼接sql上
            sql.append(tableName);
//        声明俩个集合 分别存储列名 列值
//        列值
            ArrayList<Object> values = new ArrayList<Object>();
//        列名
            ArrayList<String> columns = new ArrayList<String>();


//        获取添加字段列名通过反射类获取
            Field[] declaredFields = aClass.getDeclaredFields();
            for (Field f : declaredFields) {
//设置当前类属性值为可见性
                f.setAccessible(true);
//            判断当前类的属性id是否为空
                if (f.getAnnotation(AnMyTableFieldId.class) == null || f.get(t) != null) {
//                当id值等于空时添加
                    String name = f.getName();
//                    通过泛型添加值
                    Object value = f.get(t);
//                    将名字存到定义的类名数组中
                    columns.add(name);
//                    值存到列值中 不确定值是否为字符串列值加上‘’
                    values.add("'" + value + "'");
                }
            }
//            获取到列名和列值 数据是 数组形势出现所有要把[]替换（）
            sql.append(columns.toString().replace("[", "(").replace("]", ")"));
            sql.append("values ");
            sql.append(values.toString().replace("[", "(").replace("]", ")"));

            System.out.println(sql);
//          数据库连接的
            conn = DbUtil.getConn();
            ps = conn.prepareStatement(sql.toString());
            int i = ps.executeUpdate();
            return i;
        } catch (Exception e) {
            DbUtil.close(null, ps, conn);
        }
        return 0;

    }

    //    修改 update  表名 set 字段=值 where id=id;
    public int update(T t) {
        try {
            StringBuffer sql = new StringBuffer("update ");
//      1.  获取表名，
            Class<?> aClass = t.getClass();
//        通过注解获取数据库中对应到表名
            AnMyTableName tableNamean = aClass.getAnnotation(AnMyTableName.class);
            String tablename = tableNamean.value();
            sql.append(tablename + " set ");
//        获取values值
            Field[] declaredFields = aClass.getDeclaredFields();
//        获取条件
            String where = " where ";
            for (Field f : declaredFields) {
//            设置可见性
                f.setAccessible(true);
//            获取到列名中的id 通过判断修改数据
                AnMyTableFieldId annotation = f.getAnnotation(AnMyTableFieldId.class);
//            得到数据
                String name = f.getName();
                Object value = f.get(t);
                /*if (annotation.equals("")||annotation!=null)*/
                if (annotation == null || annotation.equals("")) {
                    sql.append(name + "='" + value + "',");
                } else {
                    where += name + "='" + value + "'";
                }
            }
//            截取掉where前的，号
            String s = sql.substring(0, sql.lastIndexOf(",")) + where;


            Connection conn = DbUtil.getConn();
            ps = conn.prepareStatement(s);
//            System.out.println(s);
            int i = ps.executeUpdate();
            return i;

        } catch (Exception e) {

        } finally {
            DbUtil.close(null, ps, conn);
        }
        return 0;
    }

    //    删除 delete from 表名
    public int delete(Object id) {
        try {
            StringBuffer sql = new StringBuffer("delete from ");
//        获取实体类的反射对象   表名
            String tableName = aClass.getAnnotation(AnMyTableName.class).value();
            sql.append(tableName + " where ");
//        获取主键
            Field[] declaredFields = aClass.getDeclaredFields();
//        循环得到id
            for (Field f : declaredFields) {
//            设置字段可见性
                f.setAccessible(true);
//            获取id值
                AnMyTableFieldId annotation = f.getAnnotation(AnMyTableFieldId.class);
//            判断id是否为空删除
                if (annotation != null) {
//                获取列名
                    String vaid = annotation.value();
//              拼接到SQL中
                    sql.append(vaid + "='" + id + "'");
//                获取到可以停止然后删除
                    break;
                }

            }
//        获取数据链接对象
            conn = DbUtil.getConn();
            ps = conn.prepareStatement(sql.toString());
            int i = ps.executeUpdate();
            return i;
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } finally {
            DbUtil.close(null, ps, conn);
        }


        return 0;
    }
}

db.properties

# druid.properties文件的配置
driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/tranbook?serverTimezone=Asia/Shanghai
username=root
password=root
# 初始化连接数量
initialSize=5
# 最大连接数
maxActive=10
# 最大超时时间
maxWait=3000

Test

public class Test01 {

    @Test
//    根据id查
    public void Test11(){

            AccountDao accountDao = new AccountDao();
            Account a = accountDao.findById("哈哈哈21");
            System.out.println(a);
        }

@Test
//添加
public void Test12(){
    AccountDao accountDao = new AccountDao();
    Account account = new Account();
    account.setUsername("哈哈哈");
    account.setBalance(12);
    int insert = accountDao.insert(account);
    System.out.println("添加成功"+insert);
}
    @Test
//修改
    public void Test13(){
        AccountDao accountDao = new AccountDao();
        Account account = new Account();
        account.setUsername("哈哈哈");
        account.setBalance(15);
        int update = accountDao.update(account);
        System.out.println("修改成功"+update);
    }
    @Test
//   删除id
    public void Test14(){

        AccountDao accountDao = new AccountDao();
        int a = accountDao.delete("哈哈哈");
        System.out.println(a);
    }
    @Test
//    根据id查
    public void Test15(){

        AccountDao accountDao = new AccountDao();
        List<Account> all = accountDao.findAll();
        System.out.println(all);
    }
}