• 手撸spring05: 解析数据源 加入事务管理 封装连接数据库 并解析返回结果集代理映射

    之前只是简单的走了一波代理还有sql打印, 不过实际应用中还是要去封装JDBC来连接数据库,进行增删查改还有事务管理.

    Transaction

    事务管理接口

    package com.linnine.mybatis.transaction;

    /**
 * @author linnine09
 * @create 2022/7/25 16:17
 */
public interface Transaction {

    /**
     * 获取连接
     * @return 返回连接
     * @throws SQLException
     */
    Connection getConnection() throws SQLException;

    /**
     * 提交事务
     * @throws SQLException
     */
    void commit() throws SQLException;

    /**
     * 回滚
     * @throws SQLException
     */
    void rollback() throws SQLException;

    /**
     * 关闭连接
     * @throws SQLException
     */
    void close() throws SQLException;
}


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    TransactionFactory

    事务工厂 用于生产事务类

    package com.linnine.mybatis.transaction;

    /**
 * 事务工厂
 * @author linnine09
 * @create 2022/7/25 16:38
 */
public interface TransactionFactory {

    /**
     * 根据Connection 创建 事务
     * @param connection
     * @return
     */
    Transaction newTransaction(Connection connection);

    /**
     * 根据数据源和数据隔离级别创建事务
     * @param dataSource
     * @param level
     * @param autoCommit
     * @return
     */
    Transaction newTransaction(DataSource dataSource, TransactionIsolationLevel level,boolean autoCommit);
}


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    JdbcTransaction

    jdbc实现事务类

    package com.linnine.mybatis.transaction.jdbc;

    
/**
 * 事务管理
 * @author linnine09
 * @create 2022/7/25 16:21
 */
public class JdbcTransaction implements Transaction {

    protected Connection connection;

    protected DataSource dataSource;

    protected TransactionIsolationLevel level = TransactionIsolationLevel.NONE;

    protected boolean autoCommit;

    public JdbcTransaction(DataSource dataSource, TransactionIsolationLevel level, boolean autoCommit) {
        this.dataSource = dataSource;
        this.level = level;
        this.autoCommit = autoCommit;
    }

    public JdbcTransaction(Connection connection) {
        this.connection = connection;
    }

    @Override
    public Connection getConnection() throws SQLException {
        Connection connection = dataSource.getConnection();
        connection.setTransactionIsolation(level.getLevel());
        connection.setAutoCommit(autoCommit);
        return connection;
    }

    @Override
    public void commit() throws SQLException {
        if (connection != null && !connection.getAutoCommit()){
            connection.commit();
        }
    }

    @Override
    public void rollback() throws SQLException {
        if (connection != null && !connection.getAutoCommit()){
            connection.rollback();
        }
    }

    @Override
    public void close() throws SQLException {
        if (connection != null && !connection.getAutoCommit()){
            connection.close();
        }
    }
}


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    TransactionIsolationLevel

    事务级别封装成枚举类

    package com.linnine.mybatis.session;

    /**
 * @author linnine09
 * @create 2022/7/25 16:25
 */
@AllArgsConstructor
@Getter
public enum TransactionIsolationLevel {
    //包括JDBC支持的5个级别
    NONE(Connection.TRANSACTION_NONE),
    READ_COMMITTED(Connection.TRANSACTION_READ_COMMITTED),
    READ_UNCOMMITTED(Connection.TRANSACTION_READ_UNCOMMITTED),
    REPEATABLE_READ(Connection.TRANSACTION_REPEATABLE_READ),
    SERIALIZABLE(Connection.TRANSACTION_SERIALIZABLE)
    ;
    
    private final int level;
}


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    JdbcTransactionFactory

    jdbc事务工厂实现类

    package com.linnine.mybatis.transaction.jdbc;

    /**
 * @author linnine09
 * @create 2022/7/25 16:57
 */
public class JdbcTransactionFactory implements TransactionFactory {
    @Override
    public Transaction newTransaction(Connection connection) {
        return new JdbcTransaction(connection);
    }

    @Override
    public Transaction newTransaction(DataSource dataSource, TransactionIsolationLevel level, boolean autoCommit) {
        return new JdbcTransaction(dataSource,level,autoCommit);
    }
}


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    TypeAliasRegistry

    基础注册器

    package com.linnine.mybatis.type;

    
/**
 * 基础注册器
 * @author linnine09
 * @create 2022/7/25 16:45
 */
public class TypeAliasRegistry {

    private final Map<String,Class<?>> TYPE_ALIASES = new HashMap<>();

    public TypeAliasRegistry(){
        // 构造函数里注册系统内置的类型别名
        registerAlias("string", String.class);

        // 基本包装类型
        registerAlias("byte", Byte.class);
        registerAlias("long", Long.class);
        registerAlias("short", Short.class);
        registerAlias("int", Integer.class);
        registerAlias("integer", Integer.class);
        registerAlias("double", Double.class);
        registerAlias("float", Float.class);
        registerAlias("boolean", Boolean.class);
    }


    /**
     * 存
     * @param alias
     * @param value
     */
    public void registerAlias(String alias, Class<?> value) {
        String key = alias.toLowerCase(Locale.ENGLISH);
        TYPE_ALIASES.put(key,value);
    }

    /**
     * 取
     * @param string
     * @param 
     * @return
     */
    public <T> Class<T> resolveAlias(String string){
        String key = string.toLowerCase(Locale.ENGLISH);
        return (Class<T>) TYPE_ALIASES.get(key);
    }

}


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    Configuration

    配置类改动,主要是加入了环境变量和上面的注册器, 并在初始化时注册事务工厂和数据源工厂.

    在这里插入图片描述

    Environment

    环境变量

    package com.linnine.mybatis.mapping;

    
/**
 * @author linnine09
 * @create 2022/7/25 17:36
 */
@Getter
public class Environment {

    private final String id;

    private final TransactionFactory transactionFactory;

    private final DataSource dataSource;

    public Environment(String id, TransactionFactory transactionFactory, DataSource dataSource) {
        this.id = id;
        this.transactionFactory = transactionFactory;
        this.dataSource = dataSource;
    }

    public static class Builder{
        private String id;
        private  TransactionFactory transactionFactory;
        private  DataSource dataSource;

        public Builder(String id) {
            this.id = id;
        }

        public Builder transactionFactory(TransactionFactory transactionFactory){
            this.transactionFactory = transactionFactory;
            return this;
        }

        public Builder dataSource(DataSource dataSource){
            this.dataSource =dataSource;
            return this;
        }
        public String id(){
            return this.id;
        }
        public Environment build(){
            return new Environment(this.id,this.transactionFactory,this.dataSource);
        }
    }
}


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    DataSourceFactory

    数据源工厂

    package com.linnine.mybatis.datasource;

    
/**
 * 数据源工厂
 * @author linnine09
 * @create 2022/7/25 17:23
 */
public interface DataSourceFactory {

    /**
     * 设置属性
     * @param props
     */
    void setProperties(Properties props);

    /**
     * 获取数据源
     * @return
     */
    DataSource getDataSource();

}


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    DruidDataSourceFactory

    德鲁伊数据源工厂 就是把属性配置填充到德鲁伊数据源中, 要导个依赖

      <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.2.11</version>
  </dependency>

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    package com.linnine.mybatis.datasource.druid;

    
/**
 * @author linnine09
 * @create 2022/7/25 16:58
 */
public class DruidDataSourceFactory implements DataSourceFactory {

    private Properties props;

    @Override
    public void setProperties(Properties props) {
        this.props=props;
    }

    @Override
    public DataSource getDataSource() {
        DruidDataSource dataSource = new DruidDataSource();
        dataSource.setDriverClassName(props.getProperty("driver"));
        dataSource.setUrl(props.getProperty("url"));
        dataSource.setUsername(props.getProperty("username"));
        dataSource.setPassword(props.getProperty("password"));
        return dataSource;
    }
}


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    MappedStatement

    整合一下里面的字段,顺便搬了个家 从binding.mapping 搬到mapping下面

    package com.linnine.mybatis.mapping;

    在这里插入图片描述

    BoundSql

    整合xml文件中每个sql的相关字段

    package com.linnine.mybatis.mapping;

    /**
 * 绑定的SQL,是从SqlSource而来，将动态内容都处理完成得到的SQL语句字符串，其中包括?,还有绑定的参数
 * @author linnine09
 * @create 2022/7/25 17:54
 */
@Data
@AllArgsConstructor
public class BoundSql {

    /**
     * sql语句
     */
    private String sql;

	/**
     * 解析占位符
     */
    private Map<Integer,String> parameterMappings;

    /**
     * 参数类型
     */
    private String parameterType;

    /**
     * 返回类型
     */
    private String resultType;

}

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    BaseBuilder

    加入基础注册器,方便xml解析器直接使用

    在这里插入图片描述

    XMLConfigBuilder

    加入了环境配置解析

    package com.linnine.mybatis.builder.xml;

    
/**
 * xml 解析类
 *
 * @author linnine09
 */
public class XMLConfigBuilder extends BaseBuilder {

    private Element root;

    public XMLConfigBuilder(Reader reader) {
        super(new Configuration());
        SAXReader saxReader = new SAXReader();
        try {
            Document document = saxReader.read(new InputSource(reader));
            root =document.getRootElement();
        } catch (DocumentException e) {
            e.printStackTrace();
        }

    }

    public Configuration parse() {

        try {
            // 环境
            environmentsElement(root.element("environments"));
            //解析映射器
            mapperElement(root.element("mappers"));
        } catch (Exception e) {
            throw new RuntimeException("Error parsing SQL Mapper Configuration. Cause: " + e, e);
        }
        return configuration;
    }

    /**
     * 解析默认环境配置
     * @param context
     * @throws Exception
     */
    private void environmentsElement(Element context) throws Exception {
        String environment = context.attributeValue("default");
        List<Element> environmentList = context.elements("environment");
        for (Element e : environmentList) {
            String id = e.attributeValue("id");
            if (environment.equals(id)){
                TransactionFactory txFactory = (TransactionFactory) typeAliasRegistry.resolveAlias(e.element("transactionManager").attributeValue("type")).newInstance();
                Element dataSourceElement = e.element("dataSource");
                DataSourceFactory dataSourceFactory = (DataSourceFactory) typeAliasRegistry.resolveAlias(dataSourceElement.attributeValue("type")).newInstance();
                List<Element> propertyList = dataSourceElement.elements("property");
                Properties props = new Properties();
                for (Element property : propertyList) {
                    props.setProperty(property.attributeValue("name"),property.attributeValue("value"));
                }
                dataSourceFactory.setProperties(props);
                DataSource dataSource = dataSourceFactory.getDataSource();
                Environment.Builder build = new Environment.Builder(id)
                        .transactionFactory(txFactory)
                        .dataSource(dataSource)
                        ;
                configuration.setEnvironment(build.build());
            }
        }
    }

    private void mapperElement(Element mappers) throws Exception {
        List<Element> mapperList = mappers.elements("mapper");
        for (Element e : mapperList) {
            String resource = e.attributeValue("resource");
            Reader reader = Resources.getResourceAsReader(resource);
            SAXReader saxReader = new SAXReader();
            Document document = saxReader.read(new InputSource(reader));
            Element root = document.getRootElement();
            String namespace = root.attributeValue("namespace");
            List<Element> selectNodes = root.elements("select");
            for (Element node : selectNodes) {
                String id = node.attributeValue("id");
                String parameterType = node.attributeValue("parameterType");
                String resultType = node.attributeValue("resultType");
                String sql = node.getText();
                Map<Integer, String> parameter = new HashMap<>();
                //匹配参数占位符
                Pattern pattern = Pattern.compile("(#\\{(.*?)})");
                Matcher matcher = pattern.matcher(sql);
                for (int i = 1; matcher.find(); i++) {
                    String g1 = matcher.group(1);
                    String g2 = matcher.group(2);
                    parameter.put(i,g2);
                    sql = sql.replace(g1, "?");
                }
                String msId=namespace+"."+id;
                String nodeName = node.getName();
                SqlCommandType sqlCommandType=SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));
                //解析处理
                MappedStatement mappedStatement = new MappedStatement.Builder(configuration,msId,sqlCommandType,new BoundSql(sql,parameter,parameterType,resultType)).build();
                //添加解析后的sql
                configuration.addMappedStatement(mappedStatement);
            }
            configuration.addMapper(Resources.classForName(namespace));
        }
    }
}


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    DefaultSqlSession

    改造内部实现

    package com.linnine.mybatis.session.defaults;

    /**
 * sql执行和结果封装
 * @author linnine09
 * @create 2022/7/25 17:45
 */
public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <T> T selectOne(String statement, Object parameter) {
        MappedStatement mappedStatement = configuration.getMappedStatement(statement);

        Environment environment = configuration.getEnvironment();

        try {
            //连接数据库
            Connection connection = environment.getDataSource().getConnection();
            //获取查询内容
            BoundSql boundSql = mappedStatement.getBoundSql();
            //填充sql
            PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSql());
            //填充参数 后面应该还得改造 从parameterMapping中取出来遍历放进去
            preparedStatement.setLong(1,Long.parseLong(((Object[])parameter)[0].toString()));
            //执行查询
            ResultSet resultSet = preparedStatement.executeQuery();
            //查询出来映射
            List<T> objList = resultSet2Obj(resultSet,Class.forName(boundSql.getResultType()));
            return objList.get(0);
        } catch (Exception e) {
            e.printStackTrace();
            return  null;
        }
    }

    private <T> List<T> resultSet2Obj(ResultSet resultSet, Class<?> clazz) {
        List<T> list = new ArrayList<>();
        try {
            ResultSetMetaData metaData = resultSet.getMetaData();
            int columnCount = metaData.getColumnCount();
            while (resultSet.next()){
                T obj = (T) clazz.newInstance();
                for (int i = 1; i < columnCount; i++) {
                    Object value = resultSet.getObject(i);
                    String columnName = metaData.getColumnName(i);
                    String setMethod ="set"+columnName.substring(0,1).toUpperCase()+ columnName.substring(1);
                    Method method;
                    if (value instanceof Timestamp){
                        method = clazz.getMethod(setMethod, Date.class);
                    }else {
                        method = clazz.getMethod(setMethod,value.getClass());
                    }
                    method.invoke(obj,value);
                }
                list.add(obj);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return list;
    }

    @Override
    public <T> T getMapper(Class<T> type) {
        return configuration.getMapper(type,this);
    }
}


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    mybatis-config-datasource.xml

    加入数据源环境配置

        <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="DRUID">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://127.0.0.1:3306/testdb?useUnicode=true"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>


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    调整mapper的入参和出参类型,xml里面的自己改一下
    在这里插入图片描述

    建库建表

    CREATE DATABASE `testdb` DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci;

CREATE TABLE
    USER
    (
        id bigint NOT NULL AUTO_INCREMENT COMMENT '自增ID',
        userId VARCHAR(9) COMMENT '用户ID',
        userHead VARCHAR(16) COMMENT '用户头像',
        createTime TIMESTAMP NULL COMMENT '创建时间',
        updateTime TIMESTAMP NULL COMMENT '更新时间',
        userName VARCHAR(64),
        PRIMARY KEY (id)
    )
    ENGINE=InnoDB DEFAULT CHARSET=utf8;
    
insert into user (id, userId, userHead, createTime, updateTime, userName) values (1, '10001', '1_04', '2022-04-13 00:00:00', '2022-04-13 00:00:00', '小傅哥');    

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    一测

        public static void main(String[] args) throws IOException {
        Reader reader = Resources.getResourceAsReader("mybatis-config-datasource.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().builder(reader);
        SqlSession sqlSession = sqlSessionFactory.openSqlSession();
        IUserDao userDao = sqlSession.getMapper(IUserDao.class);
        User user = userDao.queryUserInfoById(1L);
        System.out.println(user);
    }

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    报错了,获取数据的连接时失败

    java.sql.SQLException: com.mysql.jdbc.Driver
	at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:689)
	at com.alibaba.druid.pool.DruidDataSource.resolveDriver(DruidDataSource.java:1219)
	at com.alibaba.druid.pool.DruidDataSource.init(DruidDataSource.java:888)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1403)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1399)
	at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:100)
	at com.linnine.mybatis.session.defaults.DefaultSqlSession.selectOne(DefaultSqlSession.java:34)
	at com.linnine.mybatis.binding.MapperProxy.invoke(MapperProxy.java:48)
	at com.sun.proxy.$Proxy0.queryUserInfoById(Unknown Source)
	at com.linnine.mybatis.JavaBaseApplicationTest.main(JavaBaseApplicationTest.java:36)
Caused by: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at java.lang.Class.forName0(Native Method)
	at java.lang.Class.forName(Class.java:264)
	at com.alibaba.druid.util.JdbcUtils.createDriver(JdbcUtils.java:687)
	... 9 more

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    没有加mysql的依赖

    <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.29</version>
</dependency>

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    重新运行后报错
    在这里插入图片描述
    因为之前建了个User类是空的,所以代理的时候没有找到这个setId的方法,补上

    package com.linnine.mybatis.po;

    @Data
public class User {
        private Long id;
    // 用户ID
    private String userId;
    // 用户名称
    private String userName;
    // 头像
    private String userHead;
    // 创建时间
    private Date createTime;
    // 更新时间
    private Date updateTime;
}


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    在这里插入图片描述
    查是查出来,但是好像又不完整,找到问题了, 因为在属性填充那里,Date类型用成了sql的date所以转不过去,没仔细看还真容易忽略
    在这里插入图片描述
    最后结果
    在这里插入图片描述

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  • 原文地址：https://blog.csdn.net/weixin_45369440/article/details/125991742