MyBatis(四):自定义持久层框架优化

本文所有代码已上传至码云：https://gitee.com/rangers-sun/mybatis

修改IUserDao、UserMapper.xml

package com.rangers;

import com.rangers.entity.User;

import java.util.List;

/**

 * @Author Rangers

 * @Description 用户数据库访问Dao

 * @Date 2021-03-07

 **/

public interface IUserDao {

    /**

     * @Author Rangers

     * @Description 查询所有用户信息

     * @Date 2021/3/7 10:43 上午

     * @Return: java.util.List<com.rangers.entity.User>

     **/

    public List<User> selectList();

    /**

     * @Author Rangers

     * @Description 根据条件查询单个用户信息

     * @Date 2021/3/7 10:43 上午

     * @Param user:

     * @Return: com.rangers.entity.User

     **/

    public User selectOne(User user) ;

    Integer insert(User user);

    Integer update(User user);

    Integer delete(User user);

}

<mapper namespace="com.rangers.IUserDao">

    <select id="selectOne" parameterType="com.rangers.entity.User" resultType="com.rangers.entity.User">

        select * from user where id=#{id} and name=#{name}

    </select>

    <select id="selectList" parameterType="com.rangers.entity.User" resultType="com.rangers.entity.User">

        select * from user

    </select>

    <insert id="insert" parameterType="com.rangers.entity.User" resultType="java.lang.Integer">

        insert into user(id,name,address) values(#{id},#{name},#{address})

    </insert>

    <update id="update" parameterType="com.rangers.entity.User" resultType="java.lang.Integer">

        update user set name=#{name},address=#{address} where id=#{id}

    </update>

    <delete id="delete" parameterType="com.rangers.entity.User" resultType="java.lang.Integer">

        delete from user where id=#{id}

    </delete>

</mapper>

新增SqlCommondType 修改MappedStatement、XmlMapperBuilder

package com.rangers.persistent.config;

/**

 * @Author Rangers

 * @Description

 * @Date 2021-03-08

 **/

public enum SqlCommondType {

    INSERT, DELETE, UPDATE, SELECT;

}

package com.rangers.persistent.config.pojo;

import com.rangers.persistent.config.SqlCommondType;

/**

 * @Author Rangers

 * @Description 对应Mapper中标签的信息

 * @Date 2021-03-04

 **/

public class MappedStatement {

    // id当前xml中的唯一标识

    private String id;

    // sql语句

    private String sql;

    // 参数类型

    private String paramterType;

    // 返回结果类型

    private String resultType;

    // 返回结果类型

    private SqlCommondType sqlCommondType;

    public String getId() {

        return id;

    }

    public void setId(String id) {

        this.id = id;

    }

    public String getSql() {

        return sql;

    }

    public void setSql(String sql) {

        this.sql = sql;

    }

    public String getParamterType() {

        return paramterType;

    }

    public void setParamterType(String paramterType) {

        this.paramterType = paramterType;

    }

    public String getResultType() {

        return resultType;

    }

    public void setResultType(String resultType) {

        this.resultType = resultType;

    }

    public SqlCommondType getSqlCommondType() {

        return sqlCommondType;

    }

    public void setSqlCommondType(SqlCommondType sqlCommondType) {

        this.sqlCommondType = sqlCommondType;

    }

}

package com.rangers.persistent.config;

import com.rangers.persistent.config.pojo.Configuration;

import com.rangers.persistent.config.pojo.MappedStatement;

import org.apache.commons.collections.CollectionUtils;

import org.dom4j.Document;

import org.dom4j.DocumentException;

import org.dom4j.Element;

import org.dom4j.io.SAXReader;

import java.io.InputStream;

import java.util.ArrayList;

import java.util.List;

/**

 * @Author Rangers

 * @Description 解析XxMapper.xml

 * @Date 2021-03-04

 **/

public class XmlMapperBuilder {

    private Configuration configuration;

    public XmlMapperBuilder(Configuration configuration) {

        this.configuration = configuration;

    }

    public void parse(InputStream inputStream) {

        Document document = null;

        try {

            document = new SAXReader().read(inputStream);

        } catch (DocumentException e) {

            e.printStackTrace();

        }

        Element rootElement = document.getRootElement();

        String namespace = rootElement.attributeValue("namespace");

        List<Element> elements = new ArrayList<>();

        List<Element> selectElements = rootElement.selectNodes("//select");

        elements.addAll(selectElements);

        List<Element> insertElements = rootElement.selectNodes("//insert");

        elements.addAll(insertElements);

        List<Element> updateElements = rootElement.selectNodes("//update");

        elements.addAll(updateElements);

        List<Element> deleteElements = rootElement.selectNodes("//delete");

        elements.addAll(deleteElements);

        // 解析XxMapper.xml中的标签

        this.parseLabel(namespace, elements);

    }

    private void parseLabel(String namespace, List<Element> selectElements) {

        if (CollectionUtils.isNotEmpty(selectElements)){

            selectElements.forEach(mapperElement->{

                String id = mapperElement.attributeValue("id");

                String sql = mapperElement.getTextTrim();

                String parameterType = mapperElement.attributeValue("parameterType");

                String resultType = mapperElement.attributeValue("resultType");

                String sqlCommondType = mapperElement.getName();

                MappedStatement mappedStatement = new MappedStatement();

                mappedStatement.setId(id);

                mappedStatement.setSql(sql);

                mappedStatement.setParamterType(parameterType);

                mappedStatement.setResultType(resultType);

                mappedStatement.setSqlCommondType(SqlCommondType.valueOf(sqlCommondType.toUpperCase()));

                configuration.getMappedStatementMap().put(namespace +"."+id,mappedStatement);

            });

        }

    }

}

修改SqlSession、DefaultSqlSession

package com.rangers.persistent.sqlSession;

import java.sql.SQLException;

import java.util.List;

/**

 * @Author Rangers

 * @Description

 * @Date 2021-03-04

 **/

public interface SqlSession {

    <E> List<E> selectList(String statementId,Object...param) throws Exception;

    <T> T selectOne(String statementId,Object...param) throws Exception;

    Integer insert(String statementId,Object...param) throws Exception;

    Integer update(String statementId,Object...param) throws Exception;

    Integer delete(String statementId,Object...param) throws Exception;

    void close() throws SQLException;

    <T> T getMapper(Class<T> t);

}

package com.rangers.persistent.sqlSession;

import com.rangers.persistent.config.SqlCommondType;

import com.rangers.persistent.config.pojo.Configuration;

import com.rangers.persistent.config.pojo.MappedStatement;

import com.rangers.persistent.executor.Executor;

import com.rangers.persistent.executor.SimpleExecutor;

import org.apache.commons.collections.CollectionUtils;

import java.lang.reflect.*;

import java.sql.SQLException;

import java.util.List;

/**

 * @Author Rangers

 * @Description

 * @Date 2021-03-04

 **/

public class DefaultSqlSession implements SqlSession{

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {

        this.configuration = configuration;

    }

    private Executor executor = new SimpleExecutor();

    @Override

    public <E> List<E> selectList(String statementId, Object... params) throws Exception {

        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);

        return executor.query(configuration,mappedStatement,params);

    }

    @Override

    public <T> T selectOne(String statementId, Object... params) throws Exception {

        List<Object> objects = this.selectList(statementId, params);

        if (CollectionUtils.isNotEmpty(objects)){

            if (objects.size() == 1){

                return (T) objects.get(0);

            }else {

                throw new Exception("返回多条记录");

            }

        }

        return null;

    }

    @Override

    public Integer insert(String statementId, Object... param) throws Exception {

        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);

        return executor.insert(configuration,mappedStatement,param);

    }

    @Override

    public Integer update(String statementId, Object... param) throws Exception {

        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);

        return executor.update(configuration,mappedStatement,param);

    }

    @Override

    public Integer delete(String statementId, Object... param) throws Exception {

        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);

        return executor.delete(configuration,mappedStatement,param);

    }

    @Override

    public void close() throws SQLException {

        executor.close();

    }

    /**

     * @Author Rangers

     * @Description 使用JDK动态代理获取执行的Mapper对象

     **/

    @Override

    public <T> T getMapper(Class<T> t) {

        Object o = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{t}, new InvocationHandler() {

            @Override

            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

                // 全限定性类名==XxMapper.xml的namespace

                String className = method.getDeclaringClass().getName();

                // 接口的方法名称==XxMapper.xml的每个mapper标签的id

                String methodName = method.getName();

                // 1、构造statementID：namespace+"."+id

                String statementId = className+"."+methodName;

                // 2、定位方法执行，获取执行结果

                Object result = new Object();

                MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);

                SqlCommondType sqlCommondType = mappedStatement.getSqlCommondType();

                switch (sqlCommondType){

                    case INSERT:

                        result = insert(statementId,args);

                        break;

                    case DELETE:

                        result = delete(statementId,args);

                        break;

                    case UPDATE:

                        result = update(statementId,args);

                        break;

                    case SELECT:

                        // 获取被调用方法的返回值

                        Type returnType = method.getGenericReturnType();

                        if (returnType instanceof ParameterizedType){

                            result = selectList(statementId, args);

                        }else{

                            result = selectOne(statementId,args);

                        }

                        break;

                    default:

                        throw new Exception("statementId:"+statementId+",操作类型:"+sqlCommondType+"有误");

                }

                return result;

            }

        });

        return (T) o;

    }

}

修改Executor、SimpleExecutor

package com.rangers.persistent.executor;

import com.rangers.persistent.config.pojo.Configuration;

import com.rangers.persistent.config.pojo.MappedStatement;

import java.sql.SQLException;

import java.util.List;

/**

 * @Author Rangers

 * @Description

 * @Date 2021-03-04

 **/

public interface Executor {

    <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object...param) throws Exception;

    Integer insert(Configuration configuration, MappedStatement mappedStatement, Object...param) throws Exception;

    Integer update(Configuration configuration, MappedStatement mappedStatement, Object...param) throws Exception;

    Integer delete(Configuration configuration, MappedStatement mappedStatement, Object...param) throws Exception;

    void close() throws SQLException;

}

package com.rangers.persistent.executor;

import com.mchange.v2.c3p0.impl.NewProxyPreparedStatement;

import com.rangers.persistent.config.pojo.Configuration;

import com.rangers.persistent.config.pojo.MappedStatement;

import com.rangers.persistent.utils.GenericTokenParser;

import com.rangers.persistent.utils.ParameterMapping;

import com.rangers.persistent.utils.ParameterMappingTokenHandler;

import org.apache.commons.collections.CollectionUtils;

import java.beans.PropertyDescriptor;

import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.sql.*;

import java.util.ArrayList;

import java.util.List;

/**

 * @Author Rangers

 * @Description

 * @Date 2021-03-04

 **/

public class SimpleExecutor implements Executor {

    private Connection connnection = null;

    @Override

    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {

        PreparedStatement preparedStatement = this.getPreparedStatement(configuration, mappedStatement, params);

        // 5、执行SQL语句

        ResultSet resultSet = preparedStatement.executeQuery();

        // 6、封装返回结果集

        // 获取SQL的执行结果类型

        String resultType = mappedStatement.getResultType();

        Class<?> resultTypeClazz = getClassType(resultType);

        List<E> results = new ArrayList<>();

        // 遍历封装结果集为返回值类型

        while (resultSet.next()) {

            // 获取结果集的元数据

            ResultSetMetaData metaData = resultSet.getMetaData();

            E e = (E) resultTypeClazz.newInstance();

            if (metaData.getColumnCount() > 0) {

                for (int i = 1; i <= metaData.getColumnCount(); i++) {

                    // 字段名称

                    String columnName = metaData.getColumnName(i);

                    // 字段值

                    Object columnValue = resultSet.getObject(columnName);

                    // 使用反射或者内省，根据数据库表与实体的对应关系，完成结果集封装

                    PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName,resultTypeClazz);

                    Method writeMethod = propertyDescriptor.getWriteMethod();

                    writeMethod.invoke(e,columnValue);

                }

            }

            results.add(e);

        }

        return results;

    }

    @Override

    public Integer insert(Configuration configuration, MappedStatement mappedStatement, Object... param) throws Exception {

        return this.update(configuration,mappedStatement,param);

    }

    @Override

    public Integer update(Configuration configuration, MappedStatement mappedStatement, Object... param) throws Exception {

        PreparedStatement preparedStatement = this.getPreparedStatement(configuration, mappedStatement, param);

        return preparedStatement.executeUpdate();

    }

    @Override

    public Integer delete(Configuration configuration, MappedStatement mappedStatement, Object... param) throws Exception {

        return this.update(configuration,mappedStatement,param);

    }

    private PreparedStatement getPreparedStatement(Configuration configuration, MappedStatement mappedStatement, Object[] params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException {

        // 1、获取数据库链接

        connnection = configuration.getDataSource().getConnection();

        // 2、解析SQL语句中的#/$，及参数列表，封装为BoundSql对象

        BoundSql boundSql = getBoundSQL(mappedStatement.getSql());

        // 替换后的SQL语句

        String finalSql = boundSql.getSqlText();

        // 3、获取PreparedStatement对象

        PreparedStatement preparedStatement = connnection.prepareStatement(finalSql);

        // 4、设置参数

        // 获取传入参数类型

        String parameterType = mappedStatement.getParamterType();

        Class<?> parameterTypeClazz = getClassType(parameterType);

        // 获取SQL语句中需要替换的的参数列表

        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();

        if (CollectionUtils.isNotEmpty(parameterMappingList)) {

            for (int i = 0; i < parameterMappingList.size(); i++) {

                ParameterMapping parameterMapping = parameterMappingList.get(i);

                // SQL语句中解析出的占位参数名称

                String content = parameterMapping.getContent();

                // 利用反射从入参列表中获取数据

                Field declaredField = parameterTypeClazz.getDeclaredField(content);

                // 设置暴力访问

                declaredField.setAccessible(true);

                // 此处默认传入参数类型为对象

                Object param = declaredField.get(params[0]);

                preparedStatement.setObject(i + 1, param);

            }

        }

        // 打印执行语句

        this.printSql(preparedStatement);

        return preparedStatement;

    }

    private void printSql(PreparedStatement preparedStatement) throws NoSuchFieldException, IllegalAccessException {

        NewProxyPreparedStatement tmpPs = (NewProxyPreparedStatement) preparedStatement;

        Field inner = preparedStatement.getClass().getDeclaredField("inner");

        inner.setAccessible(true);

        String sqlLog = inner.get(tmpPs).toString();

        System.out.println("执行SQL:"+sqlLog.substring(sqlLog.lastIndexOf(":")+1));

    }

    private Class<?> getClassType(String type) throws ClassNotFoundException {

        if (type != null && type!="") {

            return Class.forName(type);

        }

        return null;

    }

    private BoundSql getBoundSQL(String sql) {

        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();

        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);

        String parseSql = genericTokenParser.parse(sql);

        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();

        return new BoundSql(parseSql, parameterMappings);

    }

    @Override

    public void close() throws SQLException {

        connnection.close();

    }

}

拆分测试类直接获取与动态代理

package com.rangers.mypersistent;

import com.rangers.entity.User;

import com.rangers.persistent.sqlSession.SqlSession;

import com.rangers.persistent.sqlSessionFactory.SqlSessionFactory;

import com.rangers.persistent.sqlSessionFactory.SqlSessionFactoryBuilder;

import com.rangers.persistent.utils.Resources;

import org.dom4j.DocumentException;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

import java.beans.PropertyVetoException;

import java.io.InputStream;

import java.sql.SQLException;

import java.util.List;

/**

 * @Author Rangers

 * @Description

 * @Date 2021-03-04

 **/

public class MyPersistentTest {

    private SqlSession sqlSession;

    @Before

    public void before() throws PropertyVetoException, DocumentException {

        // 加载配置文件

        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");

        // 解析XML文件为对象，构造SqlSessionFactory

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        sqlSession = sqlSessionFactory.openSession();

    }

    @Test

    public void selectList() throws Exception {

        List<User> users = sqlSession.selectList("com.rangers.IUserDao.selectList", null);

        System.out.println(users.toString());;

    }

    @Test

    public void selectOne() throws Exception {

        User user = new User();

        user.setId(2);

        user.setName("莉莉");

        User result = sqlSession.selectOne("com.rangers.IUserDao.selectOne", user);

        System.out.println(result.toString());

    }

    @Test

    public void insert() throws Exception {

        User user = new User();

        user.setId(3);

        user.setName("bug");

        user.setAddress("北京");

        boolean insertFlag = sqlSession.insert("com.rangers.IUserDao.insert",user) > 0;

        System.out.println("新增标识："+insertFlag);

    }

    @Test

    public void update() throws Exception {

        User user = new User();

        user.setId(3);

        user.setName("虫子");

        user.setAddress("北京");

        boolean updateFlag = sqlSession.update("com.rangers.IUserDao.update", user)>0;

        System.out.println("修改标识："+updateFlag);

    }

    @Test

    public void delete() throws Exception {

        User user = new User();

        user.setId(3);

        boolean updateFlag = sqlSession.update("com.rangers.IUserDao.delete", user)>0;

        System.out.println("删除标识："+updateFlag);

    }

    @After

    public void after() throws SQLException {

        sqlSession.close();

    }

}

package com.rangers.mypersistent;

import com.rangers.IUserDao;

import com.rangers.entity.User;

import com.rangers.persistent.sqlSession.SqlSession;

import com.rangers.persistent.sqlSessionFactory.SqlSessionFactory;

import com.rangers.persistent.sqlSessionFactory.SqlSessionFactoryBuilder;

import com.rangers.persistent.utils.Resources;

import org.dom4j.DocumentException;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

import java.beans.PropertyVetoException;

import java.io.InputStream;

import java.sql.SQLException;

import java.util.List;

/**

 * @Author Rangers

 * @Description

 * @Date 2021-03-08

 **/

public class MapperTest {

    private SqlSession sqlSession;

    @Before

    public void before() throws PropertyVetoException, DocumentException {

        // 加载配置文件

        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");

        // 解析XML文件为对象，构造SqlSessionFactory

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        sqlSession = sqlSessionFactory.openSession();

    }

    @Test

    public void mapperSelectOne() throws Exception {

        User userParam = new User();

        userParam.setId(2);

        userParam.setName("莉莉");

        IUserDao userDao = sqlSession.getMapper(IUserDao.class);

        User result = userDao.selectOne(userParam);

        System.out.println(result.toString());

    }

    @Test

    public void mapperSelectAll() throws Exception {

        IUserDao userDao = sqlSession.getMapper(IUserDao.class);

        List<User> result = userDao.selectList();

        System.out.println(result.toString());

    }

    @Test

    public void mapperInsert() throws Exception {

        IUserDao userDao = sqlSession.getMapper(IUserDao.class);

        User user = new User();

        user.setId(3);

        user.setName("bug");

        user.setAddress("北京");

        boolean insertFlag = userDao.insert(user) > 0;

        System.out.println("新增标识："+insertFlag);

    }

    @Test

    public void mapperUpdate() throws Exception {

        IUserDao userDao = sqlSession.getMapper(IUserDao.class);

        User user = new User();

        user.setId(3);

        user.setName("虫子");

        user.setAddress("北京");

        boolean updateFlag = userDao.update(user) > 0;

        System.out.println("修改标识："+updateFlag);

    }

    @Test

    public void mapperDelete() throws Exception {

        IUserDao userDao = sqlSession.getMapper(IUserDao.class);

        User user = new User();

        user.setId(3);

        boolean deleteFlag = userDao.delete(user) > 0;

        System.out.println("删除标识："+deleteFlag);

    }

    @After

    public void after() throws SQLException {

        sqlSession.close();

    }

}

MyBatis(四):自定义持久层框架优化的更多相关文章

Mybatis学习之自定义持久层框架（七）自定义持久层框架优化
前言接上文,这里只是出于强迫症,凭借着半年前的笔记来把之前没写完的文章写完,这里是最后一篇了. 前面自定义的持久层框架存在的问题 Dao层若使用实现类,会存在代码重复,整个操作的过程模版重复(加载配 ...
MyBatis(三):自定义持久层框架实现
代码已上传至码云:https://gitee.com/rangers-sun/mybatis 新建Maven工程架构端MyPersistent.使用端MyPersistentTest,使用端引入架构 ...
MyBatis(二):自定义持久层框架思路分析
使用端引入架构端Maven依赖 SqlMapConfig.xml-数据库配置信息(数据库连接jar名称.连接URL.用户名.密码),引入Mapper.xml的路径 XxMapper.xml-SQL配 ...
Java工程师高薪训练营-第一阶段开源框架源码解析-模块一持久层框架涉及实现及MyBatis源码分析-任务一：自定义持久层框架
目录任务一:自定义持久层框架 1.1 JDBC回顾及问题分析 1.2 自定义持久层框架思路分析 1.3 IPersistence_Test编写 1.3.1 XXXMapper.xml详解 1.3.2 ...
【笔记】拉勾Java工程师高薪训练营-第一阶段开源框架源码解析-模块一持久层框架涉及实现及MyBatis源码分析-任务一：自定义持久层框架
以下笔记是我看完视频之后总结整理的,部分较为基础的知识点也做了补充,如有问题欢迎沟通. 目录任务一:自定义持久层框架 1.1 JDBC回顾及问题分析 1.2 自定义持久层框架思路分析 1.3 IPe ...
Mybatis学习之自定义持久层框架（三）自定义持久层框架：读取并解析配置文件
前言前两篇文章分别讲解了JDBC和Mybatis的基本知识,以及自定义持久层框架的设计思路,从这篇文章开始,我们正式来实现一个持久层框架. 新建一个项目首先我们新建一个maven项目,将其命名为I ...
Mybatis学习之自定义持久层框架（二）自定义持久层框架设计思路
前言上一篇文章讲到了JDBC的基本用法及其问题所在,并提出了使用Mybatis的好处,那么今天这篇文章就来说一下该如何设计一个类似Mybatis这样的持久层框架(暂时只讲思路,具体的代码编写工作从下 ...
Mybatis学习之自定义持久层框架（六）自定义持久层框架：完善CRUD方法并进行测试
前言没想到会等到半年以后才来写这篇文章,我已经不记得当初自己想要在这篇文章中写什么了,还好有一些零散的笔记留着,就对照着上一篇文章及零散的笔记,把内容给补充完吧. 完善CRUD方法完善Defaul ...
Mybatis学习之自定义持久层框架（一）为什么要用框架而不直接用JDBC？
前言说起Mybatis,相信大家都不会感到陌生,它是一款优秀的持久层框架,应用于java后端开发中,为客户端程序提供访问数据库的接口. 我们都知道,JDBC是Java语言中用来规范客户端程序如何来访 ...

随机推荐

vs2019激活码
Visual Studio 2019 Enterprise BF8Y8-GN2QH-T84XB-QVY3B-RC4DF Visual Studio 2019 Professional NYWVH-HT ...
Vulkan与DX11交互
Demo演示地址07_wintest 有什么用在android平台主流是用opengl es,android下vulkan与opengles纹理互通. 而在win平台,主流游戏还用的是DX11,如果 ...
根据直方图 histogram 进行简单的图像检索
https://github.com/TouwaErioH/Machine-Learning/tree/master/image%20identification/Histogram%20retrie ...
Pymongo 笔记
Pymongo 1.MongoDB概念 MongoDB是一种非关系型数据库(NoSQL),MongoDB数据存储于内存,内存不足则将热度低数据写回磁盘.存储的数据结构为文档.每个数据库包含若干集合(c ...
HDU 3949 XOR （线性基第k小）题解
题意: 给出\(n\)个数,求出子集异或第\(k\)小的值,不存在输出-1. 思路: 先用线性基存所有的子集,然后对线性基每一位进行消元,保证只有\(d[i]\)的\(i\)位存在1,那么这样变成了一 ...
谈一谈phar 反序列化
前言来自Secarma的安全研究员Sam Thomas发现了一种新的漏洞利用方式,可以在不使用php函数unserialize()的前提下,引起严重的php对象注入漏洞.这个新的攻击方式被他公开在了 ...
vue2 响应式细节
data 中的数据是如何处理的? 每一次实例化一个组件,都会调用 initData 然后调用 observe 方法,observe 方法调用了 new Observer(value), 并且返回 __ ...
ossutilmac64
ossutilmac64 ossutil是以命令行方式管理OSS数据的工具,提供方便.简洁.丰富的存储空间(Bucket)和文件(Object)管理命令,支持Windows.Linux. Mac平台. ...
Linux in depth
Linux in depth bash file text editor filter selector command ?
PWA & TWA
PWA & TWA https://www.bilibili.com/video/av68082979/ Service Worker workbox.js https://developer ...

MyBatis(四):自定义持久层框架优化

MyBatis(四):自定义持久层框架优化的更多相关文章

随机推荐

热门专题