使用DBUtils、动态代理以及注解实现事务控制

来源：互联网发布：淘宝网流量分析编辑：程序博客网时间：2024/05/29 09:19

主要思路：

使用ThreadLoacal来传递Connection
使用动态代理来增强service层的方法，对于CUD方法添加事务
通过注解+反射来扫描方法是否开启事务

代码

C3P0工具类

package com.fly.utils;import java.sql.Connection;import java.sql.SQLException;import javax.sql.DataSource;import com.mchange.v2.c3p0.ComboPooledDataSource;public class C3P0Utils {    private static ComboPooledDataSource dataSource = new ComboPooledDataSource();    private static ThreadLocal<Connection> threadLocal = new ThreadLocal<Connection>();    public static DataSource getDataSource() {        return dataSource;    }    public static Connection getConnnection() throws SQLException {        Connection conn = threadLocal.get();        if(conn==null){            conn = dataSource.getConnection();            threadLocal.set(conn);        }        return conn;    }    public static void closeConnection() throws SQLException {        Connection conn = threadLocal.get();        if(conn != null){            conn.setAutoCommit(true);            conn.close();            threadLocal.remove();        }    }    public static void beginTransaction() throws SQLException {        Connection connnection = getConnnection();        connnection.setAutoCommit(false);    }    public static void commitTransaction() throws SQLException {        Connection connnection = getConnnection();        connnection.commit();    }    public static void rollbackTransaction() throws SQLException {        Connection connnection = getConnnection();        connnection.rollback();    }}

Transaction注解

package com.fly.utils.annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Inherited;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * Transaction注解 * 该注解用于方法 * 如果方法上有该注解，则此方法会开启事务 * （注意，需要在该方法所在的类上添加AOP注解） */@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)@Inheritedpublic @interface Transaction {}

AOP注解

package com.fly.utils.annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Inherited;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;/** * AOP注解 * 用于类的注解， * 增加此注解后，用工厂生成bean时会自动为该对象增加一个代理对象， * 该代理对象可以对内部的方法进行注解扫描， * 如果方法含有注解@Transaction，则开启事务操作。 */@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)@Inheritedpublic @interface AOP {}

动态代理的切面InvocationHandlerImpl

package com.fly.utils.aop;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import com.fly.utils.C3P0Utils;import com.fly.utils.annotation.Transaction;/** * 用于实现事务控制 */public class InvocationHandlerImpl implements InvocationHandler {    private Object target;    public InvocationHandlerImpl() {    }    public InvocationHandlerImpl(Object target) {        this.target = target;    }    @Override    public Object invoke(Object proxy, Method method, Object[] args) throws Exception {        Object returnValue = null;        //是否开启事务注解        boolean isTransaction = method.isAnnotationPresent(Transaction.class);        if (!isTransaction) {            //如果未开启了事务            System.out.println("未开启事务");            System.out.println(method.getName());            returnValue = method.invoke(target, args);              return returnValue;          }         //如果开启事务        System.out.println("开启了事务");        System.out.println(method.getName());        try {            C3P0Utils.beginTransaction();            returnValue = method.invoke(target, args);              C3P0Utils.commitTransaction();        } catch (Exception e) {            C3P0Utils.rollbackTransaction();            throw e;        } finally {            C3P0Utils.closeConnection();        }        return returnValue;      }}

bean工厂接口与实现类

package com.fly.utils.ioc;/** * bean工厂接口 */public interface BeanFactory {    Object getBean(String id);}package com.fly.utils.ioc;import java.lang.reflect.Proxy;import java.util.HashMap;import java.util.List;import java.util.Map;import org.dom4j.Document;import org.dom4j.DocumentException;import org.dom4j.Element;import org.dom4j.io.SAXReader;import com.fly.utils.annotation.AOP;import com.fly.utils.aop.InvocationHandlerImpl;/** * 基于xml文件的bean工厂实现类 * 采用懒汉式单例模式 * 初始化时会加载对应的xml配置文件 * 默认加载applicationContext.xml */public class XmlBeanFactory implements BeanFactory {    private static XmlBeanFactory INSTANCE;    public static BeanFactory getFactory(String xmlPath) {        if (INSTANCE == null) {            synchronized(XmlBeanFactory.class) {                if (INSTANCE == null)                    INSTANCE = new XmlBeanFactory(xmlPath);                         }        }        return INSTANCE;    }    public static BeanFactory getFactory() {        if (INSTANCE == null) {            synchronized(XmlBeanFactory.class) {                if (INSTANCE == null)                    INSTANCE = new XmlBeanFactory();                            }        }        return INSTANCE;    }    @SuppressWarnings("rawtypes")    Map<String, Class> classMap = new HashMap<>();    Map<String, Object> map = new HashMap<>();    private XmlBeanFactory() {        this("applicationContext.xml");    }    private XmlBeanFactory(String xmlPath) {        try {            Document doc = new SAXReader()                    .read(BeanFactory.class.getClassLoader().getResourceAsStream(xmlPath));            Element root = doc.getRootElement();            List<Element> beans = root.elements("bean");            for (Element bean : beans) {                String classValue = bean.attributeValue("class");                String id = bean.attributeValue("id");                System.out.println(id + " " + classValue);                Class<?> clazz = Class.forName(classValue);                //懒加载，用的时候实例化                classMap.put(id, clazz);            }        } catch (DocumentException e) {            e.printStackTrace();        } catch (ClassNotFoundException e) {            e.printStackTrace();        }    }    @Override    public Object getBean(String id) {        Class<?> c = classMap.get(id);        if (c != null) {            //单例化            Object o = map.get(id);            if (o == null) {                try {                    o = c.newInstance();                    if (c.isAnnotationPresent(AOP.class)) {                        o = Proxy.newProxyInstance(this.getClass().getClassLoader(),                                o.getClass().getInterfaces(),                                new InvocationHandlerImpl(o));                    }                    map.put(id, o);                } catch (InstantiationException e) {                    e.printStackTrace();                } catch (IllegalAccessException e) {                    e.printStackTrace();                }            }        }        return map.get(id);    }}

注意：Transaction注解需要加在interface中的方法上（由于扫描注解是在invocationhandler中进行的）

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