【从零写javaweb框架】(十一)为框架添加事务处理

上一篇我们为框架添加了AOP特性【从零写javaweb框架】(十)加载AOP框架，现在可以利用这个特性来为框架添加事务处理。

定义一个事务注解:

package org.smart4j.framework.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * desc : 事务注解
 * Created by Lon on 2018/2/17.
 */
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Transaction {
}

Transaction注解可以标记在Service的方法上，表示是一个有事务的方法，如果抛出异常，则会进行回滚操作。

我们还需要一个操作数据库的工具类DatabaseHelper,它的底层是Apache common 的DBUtil，用ThreadLocal实现了线程安全，用DBCP数据连接池来提高性能:

package org.smart4j.framework.helper;

import org.apache.commons.dbcp2.BasicDataSource;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.smart4j.framework.util.CollectionUtil;
import org.smart4j.framework.util.PropsUtil;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Properties;

/**
 * desc : 数据库操作助手类
 * Created by Lon on 2018/2/17.
 */
public final class DatabaseHelper {

    private static final Logger LOGGER = LoggerFactory.getLogger(DatabaseHelper.class);

    private static final String DRIVER;
    private static final String URL;
    private static final String USERNAME;
    private static final String PASSWORD;

    // DBUtil
    private static final QueryRunner QUERY_RUNNER = new QueryRunner();

    // 隔离线程
    private static final ThreadLocal<Connection> CONNECTION_HOLDER = new ThreadLocal<Connection>();

    // DBCP数据库连接池
    private static final BasicDataSource DATA_SOURCE = new BasicDataSource();

    static {
        Properties conf = PropsUtil.loadProps("config.properties");
        DRIVER = conf.getProperty("jdbc.driver");
        URL = conf.getProperty("jdbc.url");
        USERNAME = conf.getProperty("jdbc.username");
        PASSWORD = conf.getProperty("jdbc.password");

        DATA_SOURCE.setDriverClassName(DRIVER);
        DATA_SOURCE.setUrl(URL);
        DATA_SOURCE.setUsername(USERNAME);
        DATA_SOURCE.setPassword(PASSWORD);
    }

    /**
     * 获取数据库连接
     */
    public static Connection getConnection(){
        Connection conn = CONNECTION_HOLDER.get();
        if (conn == null){
            try {
                conn = DATA_SOURCE.getConnection();
            } catch (SQLException e) {
                LOGGER.error("get connection failure", e);
                throw new RuntimeException(e);
            } finally {
                CONNECTION_HOLDER.set(conn);
            }
        }
        return conn;
    }


    /**
     * 查询实体列表
     */
    public static <T> List<T> queryEntityList(Class<T> entityClass, String sql, Object... params){
        List<T> entityList;
        try {
            Connection conn = getConnection();
            entityList = QUERY_RUNNER.query(conn, sql, new BeanListHandler<T>(entityClass), params);
        } catch (SQLException e) {
            LOGGER.error("query entity list failure", e);
            throw new RuntimeException(e);
        }
        return entityList;
    }

    /**
     * 查询实体
     */
    public static <T> T queryEntity(Class<T> entityClass, String sql, Object... params){
        T entity;
        try {
            Connection conn = getConnection();
            entity = QUERY_RUNNER.query(conn, sql, new BeanHandler<T>(entityClass), params);
        } catch (SQLException e){
            LOGGER.error("query entity failure", e);
            throw new RuntimeException(e);
        }
        return entity;
    }

    /**
     * 可进行联表查询，返回一个List<Map>
     */
    public static List<Map<String, Object>> executeQuery(String sql, Object... params){
        List<Map<String, Object>> result;
        try {
            Connection conn = getConnection();
            result = QUERY_RUNNER.query(conn, sql, new MapListHandler(), params);
        } catch (Exception e){
            LOGGER.error("execute query failure", e);
            throw new RuntimeException(e);
        }
        return result;
    }

    /**
     * 执行更新语句 (包括update/insert/delete), 返回更新的行数
     */
    public static int excuteUpdate(String sql, Object... params){
        int rows = 0;
        try {
            Connection conn = getConnection();
            rows = QUERY_RUNNER.update(conn, sql, params);
        } catch (SQLException e){
            LOGGER.error("execute update failure", e);
            throw new RuntimeException(e);
        }
        return rows;
    }

    /**
     * 插入实体
     */
    public static <T> boolean insertEntity(Class<T> entityClass, Map<String, Object> fieldMap){
        if (CollectionUtil.isEmpty(fieldMap)){
            LOGGER.error("can not insert entity");
            return false;
        }
        String sql = "INSERT INTO " + getTableName(entityClass);
        StringBuilder columns = new StringBuilder("(");
        StringBuilder values = new StringBuilder("(");
        for (String fieldName : fieldMap.keySet()){
            columns.append(fieldName).append(", ");
            values.append("?, ");
        }
        columns.replace(columns.lastIndexOf(", "), columns.length(), ")");
        values.replace(values.lastIndexOf(", "), values.length(), ")");
        sql += columns + " VALUES " + values;
        Object[] params = fieldMap.values().toArray();
        return excuteUpdate(sql, params) == 1;
    }

    /**
     * 更新实体
     */
    public static <T> boolean updateEntity(Class<T> entityClass, long id, Map<String, Object> fieldMap){
        if (CollectionUtil.isEmpty(fieldMap)){
            LOGGER.error("can not update entity: fieldMap is empty");
            return false;
        }
        String sql = "UPDATE " + getTableName(entityClass) + " SET ";
        StringBuilder columns = new StringBuilder();
        for (String fieldName : fieldMap.keySet()){
            columns.append(fieldName).append("=? ");
        }
        sql += columns.substring(0, columns.lastIndexOf(", ")) + " WHERE id=?";
        List<Object> paramList = new ArrayList<Object>();
        paramList.addAll(fieldMap.values());
        paramList.add(id);
        Object[] params = paramList.toArray();
        return excuteUpdate(sql, params) == 1;
    }

    /**
     * 删除实体
     */
    public static <T> boolean deleteEntity(Class<T> entityClass, long id){
        String sql = "DELETE FROM " + getTableName(entityClass) + " WHERE id=?";
        return excuteUpdate(sql, id) == 1;
    }

    /**
     * 执行SQL文件
     */
    public static void executeSqlFile(String filePath){
        InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream(filePath);
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        try {
            String sql;
            while ((sql=reader.readLine()) != null){
                excuteUpdate(sql);
            }
        } catch (Exception e){
            LOGGER.error("execute sql file failure", e);
            throw new RuntimeException(e);
        }
    }

    /**
     * 获取数据库表名
     */
    private static String getTableName(Class<?> entityClass){
        return entityClass.getSimpleName();
    }

    /**
     * 开启事务
     */
    public static void beginTransaction(){
        Connection conn = getConnection();
        if (conn != null){
            try {
                conn.setAutoCommit(false);
            } catch (SQLException e) {
                LOGGER.error("begin transaction failure", e);
                throw new RuntimeException(e);
            } finally {
                CONNECTION_HOLDER.set(conn);
            }
        }
    }

    /**
     * 提交事务
     */
    public static void commitTransaction(){
        Connection conn = getConnection();
        if (conn != null){
            try {
                conn.commit();
                conn.close();
            } catch (SQLException e) {
                LOGGER.error("commit transaction failure", e);
                throw new RuntimeException(e);
            } finally {
                CONNECTION_HOLDER.remove();
            }
        }
    }

    /**
     * 回滚事务
     */
    public static void rollbackTransaction(){
        Connection conn = getConnection();
        if (conn != null){
            try {
                conn.rollback();
                conn.close();
            } catch (SQLException e) {
                LOGGER.error("rollback transaction failure", e);
                throw new RuntimeException(e);
            } finally {
                CONNECTION_HOLDER.remove();
            }
        }
    }

}

有了上面的代码后，现在可以编写事务代理切面类了，它继承了Proxy接口:

package org.smart4j.framework.proxy;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.smart4j.framework.annotation.Transaction;
import org.smart4j.framework.helper.DatabaseHelper;

import java.lang.reflect.Method;

/**
 * desc : 事务代理
 * Created by Lon on 2018/2/18.
 */
public class TransactionProxy implements Proxy{

    private static final Logger LOGGER = LoggerFactory.getLogger(TransactionProxy.class);

    private static final ThreadLocal<Boolean> FLAG_HOLDER = new ThreadLocal<Boolean>(){
        @Override
        protected Boolean initialValue() {
            return false;
        }
    };

    public Object doProxy(ProxyChain proxyChain) throws Throwable {
        Object result;
        boolean flag = FLAG_HOLDER.get();
        Method method = proxyChain.getTargetMethod();
        if (!flag && method.isAnnotationPresent(Transaction.class)){
            FLAG_HOLDER.set(true);
            try {
                DatabaseHelper.beginTransaction();
                LOGGER.debug("begin transaction");
                result = proxyChain.doProxyChain();
                LOGGER.debug("commit transaction");
                DatabaseHelper.commitTransaction();
            } catch (Exception e){
                DatabaseHelper.rollbackTransaction();
                LOGGER.debug("rollback transaction");
                throw e;
            } finally {
                FLAG_HOLDER.remove();
            }
        } else {
            result = proxyChain.doProxyChain();
        }
        return result;
    }
}

其中FLAG_HOLDER是一个标志，它可以保证同一线程中事务控制相关逻辑只会执行一次，通过ProxyChain对象可以获取目标方法，进而判断该方法是否带有Transaction注解

最后就是在框架加载时，需要把事务切面也给加载进来，所以需要改动一下AopHelper类:

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    /**
     * 一个代理类会对应多个目标类(被代理的类)。
     * 这个方法会返回各个代理类与目标类 的映射关系
     */
    private static Map<Class<?>, Set<Class<?>>> createProxyMap() throws Exception{
        Map<Class<?>, Set<Class<?>>> proxyMap = new HashMap<Class<?>, Set<Class<?>>>();
        addAspectProxy(proxyMap);
        addTransactionProxy(proxyMap);
        return proxyMap;
    }

    /**
     * 添加一般的切面代理
     */
    private static void addAspectProxy(Map<Class<?>, Set<Class<?>>> proxyMap) throws Exception{
        // 获取所有继承AspectProxy类的代理类
        Set<Class<?>> proxyClassSet = ClassHelper.getClassSetBySuper(AspectProxy.class);
        // 遍历所有代理类
        for (Class<?> proxyClass : proxyClassSet){
            // 如果当前代理类有Aspect注解
            if (proxyClass.isAnnotationPresent(Aspect.class)){
                Aspect aspect = proxyClass.getAnnotation(Aspect.class);
                Set<Class<?>> targetClassSet = createTargetClassSet(aspect);
                proxyMap.put(proxyClass, targetClassSet);
            }
        }
    }

    /**
     * 添加事务代理
     */
    private static void addTransactionProxy(Map<Class<?>, Set<Class<?>>> proxyMap){
        Set<Class<?>> serviceClassSet = ClassHelper.getClassSetByAnnotation(Service.class);
        proxyMap.put(TransactionProxy.class, serviceClassSet);
    }

一个简单的事务框架就此完成