手写IOC及AOP

1.概念

IOC：Inversion of control 控制反转

• 控制：指的是对象创建（实例化、管理）的权利
• 反转：控制权交给外部环境了（spring框架、IoC容器）
• 传统开发⽅式：⽐如类A依赖于类B，往往会在类A中new⼀个B的对象
• IoC思想下开发方式：我们不⽤⾃⼰去new对象了，⽽是由IoC容器（Spring框架）去帮助我们实例化对象并且管理它，我们需要使⽤哪个对象，去问IoC容器要即可。
• 解决的问题：解决对象之间的耦合问题，避免new关键字
• Ioc和DI区别：IOC和DI是从不同角度描述同一件事情（对象实例化及依赖关系维护这件事情）。IOC是站在对象的角度，对象实例化及其管理的权力交给了（反转）容器。DI：Dependancy Injection（依赖注⼊），是站在容器的角度，容器会把对象依赖的其他对象注入（送进去），比如A对象实例化过程中因为声明了一个B类型的属性，那么就需要容器把B对象注入给A

AOP：Aspect oriented Programming 面向切面编程

• 起源：aop是oop的延续，oop三大特征：封装、继承、多态。是一种垂直纵向的继承体系。OOP编程思想可以解决⼤多数的代码重复问题，但是有⼀些情况是处理不了的，⽐如在顶级⽗类中的多个⽅法中相同位置出现了重复代码，OOP就解决不了
• 横切逻辑代码问题：1.横切代码重复问题。2.横切逻辑代码和业务代码混杂在⼀起，代码臃肿，维护不⽅便
• AOP解决的问题：在不改变原有业务逻辑情况下，增强横切逻辑代码，根本上解耦合，避免横切逻辑代码重复
• 面向切面编程理解：「切」：指的是横切逻辑，原有业务逻辑代码我们不能动，只能操作横切逻辑代码，所以⾯向横切逻辑。「⾯」：横切逻辑代码往往要影响的是很多个⽅法，每⼀个⽅法都如同⼀个点，多个点构成⾯，有⼀个⾯的概念在⾥⾯

2.通过银行转账案例手写IOC和AOP

2.1.表结构

CREATE TABLE `account` (
  `name` varchar(255) DEFAULT NULL COMMENT '用户名',
  `money` varchar(255) DEFAULT NULL COMMENT '账户金额',
  `cardNo` varchar(255) NOT NULL COMMENT '银行卡号'
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

2.2.银行转账调用关系

转账页面 TransferServlet TransferService AccountDao JdbcAccountDaoImpl MybatisAccountDaoImpl 点击'转出'，页面发起ajax，请求到TransferServlet TransferServlet中实例化service层对象，并调用service层方法- TransferService transferService = new TransferServiceImpl() TransferService中实例化dao层对象，并调用dao层方- 法 AccountDao dao=new JdbcAccountDaoImpl() Dao层实现原生JDBC 如果要切换成Mybatis实现呢？ 转账页面 TransferServlet TransferService AccountDao JdbcAccountDaoImpl MybatisAccountDaoImpl

2.3.分析存在的问题

• （1）问题⼀：在上述案例实现中，service 层实现类在使⽤ dao 层对象时，直接在TransferServiceImpl 中通过 AccountDao accountDao = new JdbcAccountDaoImpl() 获得了 dao层对象，然⽽⼀个 new 关键字却将 TransferServiceImpl 和 dao 层具体的⼀个实现类JdbcAccountDaoImpl 耦合在了⼀起，如果说技术架构发⽣⼀些变动，dao 层的实现要使⽤其它技术，⽐如 Mybatis，思考切换起来的成本？每⼀个 new 的地⽅都需要修改源代码，重新编译，⾯向接⼝开发的意义将⼤打折扣？
• （2）问题⼆：service 层代码没有竟然还没有进⾏事务控制 ？！如果转账过程中出现异常，将可能导致数据库数据错乱，后果可能会很严重，尤其在⾦融业务

2.4.解决问题思路

• 实例化对象的⽅式除了 new 之外，还有什么技术？反射 (需要把类的全限定类名配置在xml中)
• 考虑使⽤设计模式中的⼯⼚模式解耦合，另外项⽬中往往有很多对象需要实例化，那就在⼯⼚中使⽤反 射技术实例化对象，⼯⼚模式很合适
• service 层没有添加事务控制，怎么办？没有事务就添加上事务控制，⼿动控制 JDBC 的Connection 事务，但要注意将Connection和当前线程绑定（即保证⼀个线程只有⼀个Connection，这样操作才针对的是同⼀个 Connection，进⽽控制的是同⼀个事务）。分析：数据库的事务归根结底是Connection的事务connection.commit();提交事务 connection.rollback();回滚事务

2.5.通过IOC及AOP进行改造

2.5.0.pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0modelVersion>

  <groupId>com.lagou.edugroupId>
  <artifactId>lagou-transferartifactId>
  <version>1.0-SNAPSHOTversion>
  <packaging>warpackaging>

  <name>lagou-transfer Maven Webappname>
  
  <url>http://www.example.comurl>

  <properties>
    <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
    <maven.compiler.source>11maven.compiler.source>
    <maven.compiler.target>11maven.compiler.target>
  properties>


  <dependencies>
    
    <dependency>
      <groupId>junitgroupId>
      <artifactId>junitartifactId>
      <version>4.12version>
    dependency>

    
    <dependency>
      <groupId>mysqlgroupId>
      <artifactId>mysql-connector-javaartifactId>
      <version>5.1.35version>
    dependency>
    
    <dependency>
      <groupId>com.alibabagroupId>
      <artifactId>druidartifactId>
      <version>1.1.21version>
    dependency>

    
    <dependency>
      <groupId>javax.servletgroupId>
      <artifactId>javax.servlet-apiartifactId>
      <version>3.1.0version>
      <scope>providedscope>
    dependency>

    
    <dependency>
      <groupId>com.fasterxml.jackson.coregroupId>
      <artifactId>jackson-databindartifactId>
      <version>2.9.6version>
    dependency>

    
    <dependency>
      <groupId>dom4jgroupId>
      <artifactId>dom4jartifactId>
      <version>1.6.1version>
    dependency>
    
    <dependency>
      <groupId>jaxengroupId>
      <artifactId>jaxenartifactId>
      <version>1.1.6version>
    dependency>
    
    <dependency>
      <groupId>cglibgroupId>
      <artifactId>cglibartifactId>
      <version>2.1_2version>
    dependency>
  dependencies>

  <build>
    <plugins>
      
      <plugin>
        <groupId>org.apache.maven.pluginsgroupId>
        <artifactId>maven-compiler-pluginartifactId>
        <version>3.2version>
        <configuration>
          <source>11source>
          <target>11target>
          <encoding>UTF-8encoding>
        configuration>
      plugin>

      
      
      <plugin>
        <groupId>org.apache.tomcat.mavengroupId>
        <artifactId>tomcat7-maven-pluginartifactId>
        <version>2.2version>
        <configuration>
          <port>8080port>
          <path>/path>
        configuration>
      plugin>
    plugins>
  build>
project>

2.5.1.index.xml

doctype html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>转账汇款title>

    <script type="text/javascript" src="js/jquery-3.4.1.min.js">script>


    <style type="text/css">
        body {
       
            background-color:#00b38a;
            text-align:center;
        }

        .lp-login {
       
            position:absolute;
            width:500px;
            height:300px;
            top:50%;
            left:50%;
            margin-top:-250px;
            margin-left:-250px;
            background: #ffffff;
            border-radius: 4px;
            box-shadow: 0 0 10px #12a591;
            padding: 57px 50px 35px;
            box-sizing: border-box
        }


        .lp-login .submitBtn {
       
            display:block;
            text-decoration:none;
            height: 48px;
            width: 150px;
            line-height: 48px;
            font-size: 16px;
            color: #fff;
            text-align: center;
            background-image: -webkit-gradient(linear, left top, right top, from(#09cb9d), to(#02b389));
            background-image: linear-gradient(90deg, #09cb9d, #02b389);
            border-radius: 3px
        }


        input[type='text'] {
       
            height:30px;
            width:250px;
        }

        span {
       
            font-style: normal;
            font-variant-ligatures: normal;
            font-variant-caps: normal;
            font-variant-numeric: normal;
            font-variant-east-asian: normal;
            font-weight: normal;
            font-stretch: normal;
            font-size: 14px;
            line-height: 22px;
            font-family: "Hiragino Sans GB", "Microsoft Yahei", SimSun, Arial, "Helvetica Neue", Helvetica;
        }

    style>
    <script type="text/javascript">
        $(function(){
       
            $(".submitBtn").bind("click",function(){
       
                var fromAccount = $("#fromAccount").val();
                var toAccount = $("#toAccount").val();
                var money = $("#money").val();

                if(money == null || $.trim(money).length == 0){
       
                    alert("sorry,必须输入转账金额~");
                    return;
                }

                $.ajax({
       
                    url:'/transferServlet',
                    type:'POST',    //GET
                    async:false,    //或false,是否异步
                    data:{
       
                        fromCardNo:fromAccount.split(' ')[1],
                        toCardNo:toAccount.split(' ')[1],
                        money:money
                    },
                    timeout:5000,    //超时时间
                    dataType:'json', //返回的数据格式：json/xml/html/script/jsonp/text
                    success:function(data){
       
                        if("200" == data.status){
       
                            alert("转账成功~~~");
                        }else{
       
                            alert("转账失败~~~,message:" + data.message);
                        }
                    }
                })
            })
        })

        //检查输入值是否为整数
        function checkFormat(obj){
       
            var reg = /^[0-9]+[0-9]*]*$/;
            if($.trim($(obj).val()).length>0){
       
                if(!reg.test($(obj).val())){
       
                    alert("输入格式错误！请输整数！");
                    $(obj).val("");
                }else{
       
                    $(obj).val(parseInt($(obj).val()));
                }
            }
        }
    script>
head>
<body>


<form>
    <table class="lp-login">
        <tr>
            <td align="right"><span>收款账户span>td>
            <td align="center">
                <input type="text" id="toAccount" value="韩梅梅 6029621011001" disabled>input>
            td>
        tr>
        <tr>
            <td align="right"><span>付款账户span>td>
            <td align="center">
                <input type="text" id="fromAccount" value="李大雷 6029621011000" disabled>input>
            td>
        tr>
        <tr>
            <td align="right"><span>转账金额span>td>
            <td align="center">
                <input type="text" id="money" onblur="checkFormat(this)">input>
            td>
        tr>
        <tr align="center">
            <td colspan="2">
                <a href="javasrcipt:void(0)" class="submitBtn"><span>转 出span>a>
            td>
        tr>
    table>
form>

body>
html>

2.5.2.beans.xml

<beans>
    
    <bean id="accountDao" class="com.lagou.edu.dao.impl.JdbcAccountDaoImpl">
        <property name="ConnectionUtils" ref="connectionUtils">property>
    bean>
    <bean id="transferService" class="com.lagou.edu.service.impl.TransferServiceImpl">
        
        <property name="AccountDao" ref="accountDao">property>
    bean>

    
    
    <bean id="connectionUtils" class="com.lagou.edu.utils.ConnectionUtils">bean>

    
    <bean id="transactionManager" class="com.lagou.edu.utils.TransactionManager">
        <property name="ConnectionUtils" ref="connectionUtils">property>
    bean>

    
    <bean id="proxyFactory" class="com.lagou.edu.factory.ProxyFactory">
        <property name="TransactionManager" ref="transactionManager">property>
    bean>


beans>

2.5.3.工具类

• ConnectionUtils

package com.lagou.edu.utils;

import com.alibaba.druid.pool.DruidPooledConnection;

import java.sql.Connection;
import java.sql.SQLException;

/**
 * 获取数据库连接工具类
 */
public class ConnectionUtils {
     

/*    private ConnectionUtils(){}

    public static ConnectionUtils getInstance(){
        return new ConnectionUtils();
    }*/

    // 1.单例，保证线程获取到的连接是同一个。（每次新new ConnectionUtils，那么里面的threadlocal也是新的，connection也是新的）
    private ThreadLocal<Connection> threadLocal = new ThreadLocal<>();

    public Connection getCurrentThreadConn() throws SQLException {
     
        Connection connection = threadLocal.get();
        if (connection == null){
     
            connection = DruidUtils.getInstance().getConnection();
            // 创建完成后一定要设置回去
            threadLocal.set(connection);
        }
        return connection;
    }

}

• DruidUtils

package com.lagou.edu.utils;

import com.alibaba.druid.pool.DruidDataSource;


public class DruidUtils {
     

    private DruidUtils(){
     
    }

    private static DruidDataSource druidDataSource = new DruidDataSource();


    static {
     
        druidDataSource.setDriverClassName("com.mysql.jdbc.Driver");
        druidDataSource.setUrl("jdbc:mysql://localhost:3306/bank");
        druidDataSource.setUsername("root");
        druidDataSource.setPassword("123456");

    }

    public static DruidDataSource getInstance() {
     
        return druidDataSource;
    }

}

• TransactionManager

package com.lagou.edu.utils;

import java.sql.Connection;
import java.sql.SQLException;

/**
 * 事务管理器
 */
public class TransactionManager {
     

    private ConnectionUtils connectionUtils;

    public void setConnectionUtils(ConnectionUtils connectionUtils) {
     
        this.connectionUtils = connectionUtils;
    }
    /*    private TransactionManager(){}

    private static TransactionManager transactionManager = new TransactionManager();

    public static TransactionManager getInstance(){
        return transactionManager;
    }*/

    public void beginTranscation() throws SQLException {
     
        Connection conn = connectionUtils.getCurrentThreadConn();
        conn.setAutoCommit(false);
        System.out.println(conn.getAutoCommit() + "：开启事务的连接:"+conn);
    }

    public void commit() throws SQLException {
     
        connectionUtils.getCurrentThreadConn().commit();
        System.out.println("提交的连接:"+connectionUtils.getCurrentThreadConn());
    }

    public void rollback() throws SQLException {
     
        connectionUtils.getCurrentThreadConn().rollback();
        System.out.println("回滚的连接:"+connectionUtils.getCurrentThreadConn());
    }

}

• JsonUtils

package com.lagou.edu.utils;

import java.util.List;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
 * JSON工具类（使用的是jackson实现的）
 */
public class JsonUtils {
     

    private static final ObjectMapper MAPPER = new ObjectMapper();

    /**
     * 将对象转换成json字符串。
     * @param data
     * @return
     */
    public static String object2Json(Object data) {
     
    	try {
     
			String string = MAPPER.writeValueAsString(data);
			return string;
		} catch (JsonProcessingException e) {
     
			e.printStackTrace();
		}
    	return null;
    }
    
    /**
     * 将json结果集转化为对象
     * 
     * @param jsonData json数据
     * @param beanType 对象中的object类型
     * @return
     */
    public static <T> T json2Pojo(String jsonData, Class<T> beanType) {
     
        try {
     
            T t = MAPPER.readValue(jsonData, beanType);
            return t;
        } catch (Exception e) {
     
        	e.printStackTrace();
        }
        return null;
    }
    
    /**
     * 将json数据转换成pojo对象list
     * @param jsonData
     * @param beanType
     * @return
     */
    public static <T>List<T> json2List(String jsonData, Class<T> beanType) {
     
    	JavaType javaType = MAPPER.getTypeFactory().constructParametricType(List.class, beanType);
    	try {
     
    		List<T> list = MAPPER.readValue(jsonData, javaType);
    		return list;
		} catch (Exception e) {
     
			e.printStackTrace();
		}
    	
    	return null;
    }
    
}

2.5.4.pojo

• Account

package com.lagou.edu.pojo;


public class Account {
     

    private String cardNo;
    private String name;
    private int money;

    public String getName() {
     
        return name;
    }

    public void setName(String name) {
     
        this.name = name;
    }

    public int getMoney() {
     
        return money;
    }

    public void setMoney(int money) {
     
        this.money = money;
    }

    public String getCardNo() {
      return cardNo; }

    public void setCardNo(String cardNo) {
      this.cardNo = cardNo;}

    @Override
    public String toString() {
     
        return "Account{" +
                "cardNo='" + cardNo + '\'' +
                ", name='" + name + '\'' +
                ", money=" + money +
                '}';
    }
}

2.5.5.工厂类

• BeanFactory

package com.lagou.edu.factory;

import org.dom4j.DocumentException;
import org.dom4j.Element;
import org.dom4j.io.SAXReader;

import java.io.InputStream;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * 工厂类
 * 作用1：解析xml文件，使用反射技术实例化bean对象，放入map中待用；
 * 作用2：提供接口方法根据id从map中获取bean（静态方法）
 *
 */
public class BeanFactory {
     

    private static Map<String,Object> map = new HashMap<>();

   // 0.服务一启动，就将对象加载至容器中，这里使用静态代码块
    static{
     
        // 1.解析对象配置文件
       InputStream resourceAsStream = BeanFactory.class.getClassLoader().getResourceAsStream("beans.xml");
       try {
     
           // 使用dom4j技术,首先获取根节点 
           Element rootElement = new SAXReader().read(resourceAsStream).getRootElement();
           // 使用xpath，寻找  节点
           List<Element> beanList = rootElement.selectNodes("//bean");
           for (Element element : beanList) {
     
               String id = element.attributeValue("id");
               String aClass = element.attributeValue("class");
               // 2.使用反射技术，根据类的全路径创建对象
               Class<?> aClass1 = Class.forName(aClass);
               Object o = aClass1.newInstance();

               // 3.将解析后的对象放入容器中（map）
               map.put(id,o);
           }

           // 遍历property标签，将属性注入，维护bean之间的依赖关系
           List<Element> propertyList = rootElement.selectNodes("//property");
           for (Element element : propertyList) {
     
               String name = element.attributeValue("name");
               String ref = element.attributeValue("ref");

               // 使用反射技术，设置属性
               Element parent = element.getParent();
               String parentId = parent.attributeValue("id");
               Object parentObj = map.get(parentId);
               Method[] methods = parentObj.getClass().getMethods();
               // 获取所有方法，寻找set+name，将ref设置
               for (Method method : methods) {
     
                   if(method.getName().equalsIgnoreCase("set"+name)){
     
                       Object propertyObj = map.get(ref);
                       method.invoke(parentObj,propertyObj);
                   }
               }
               // 维护依赖关系后重新将bean放入map中
               map.put(parentId,parentObj);
           }





       } catch (DocumentException | ClassNotFoundException e) {
     
           e.printStackTrace();
       } catch (IllegalAccessException e) {
     
           e.printStackTrace();
       } catch (InstantiationException e) {
     
           e.printStackTrace();
       } catch (InvocationTargetException e) {
     
           e.printStackTrace();
       }


   }

    // 3.提供获取对象的方法
    public static Object getBean(String id){
     
        return map.get(id);
    }


}

• ProxyFactory

package com.lagou.edu.factory;

import com.lagou.edu.utils.TransactionManager;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

/**
 *
 * 代理对象工厂：生成代理对象的
 */

public class ProxyFactory {
     


    private TransactionManager transactionManager;

    public void setTransactionManager(TransactionManager transactionManager) {
     
        this.transactionManager = transactionManager;
    }

     /*private ProxyFactory(){

    }

   private static ProxyFactory proxyFactory = new ProxyFactory();

    public static ProxyFactory getInstance() {
        return proxyFactory;
    }*/



    /**
     * Jdk动态代理
     * @param obj  委托对象
     * @return   代理对象
     */
    public Object getJdkProxy(Object obj) {
     

        // 获取代理对象
        return  Proxy.newProxyInstance(obj.getClass().getClassLoader(), obj.getClass().getInterfaces(),
                new InvocationHandler() {
     
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
     
                        Object result = null;

                        try{
     
                            // 开启事务(关闭事务的自动提交)
                            transactionManager.beginTranscation();

                            result = method.invoke(obj,args);

                            // 提交事务

                            transactionManager.commit();
                        }catch (Exception e) {
     
                            e.printStackTrace();
                            // 回滚事务
                            transactionManager.rollback();

                            // 抛出异常便于上层servlet捕获
                            throw e;

                        }

                        return result;
                    }
                });

    }


    /**
     * 使用cglib动态代理生成代理对象
     * @param obj 委托对象
     * @return
     */
    public Object getCglibProxy(Object obj) {
     
        return  Enhancer.create(obj.getClass(), new MethodInterceptor() {
     
            @Override
            public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
     
                Object result = null;
                try{
     
                    // 开启事务(关闭事务的自动提交)
                    transactionManager.beginTranscation();

                    result = method.invoke(obj,objects);

                    // 提交事务
                    transactionManager.commit();
                }catch (Exception e) {
     

                    // 回滚事务
                    transactionManager.rollback();

                    e.printStackTrace();

                    // 抛出异常便于上层servlet捕获
                    throw e;

                }
                return result;
            }
        });
    }
}

2.5.6.dao层

• AccountDao

package com.lagou.edu.dao;

import com.lagou.edu.pojo.Account;


public interface AccountDao {
     

    Account queryAccountByCardNo(String cardNo) throws Exception;

    int updateAccountByCardNo(Account account) throws Exception;
}

• JdbcAccountDaoImpl

package com.lagou.edu.dao.impl;

import com.lagou.edu.pojo.Account;
import com.lagou.edu.dao.AccountDao;
import com.lagou.edu.utils.ConnectionUtils;
import com.lagou.edu.utils.DruidUtils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;


public class JdbcAccountDaoImpl implements AccountDao {
     

    private ConnectionUtils connectionUtils;

    public void setConnectionUtils(ConnectionUtils connectionUtils) {
     
        this.connectionUtils = connectionUtils;
    }


    public void init() {
     
        System.out.println("初始化方法.....");
    }

    public void destory() {
     
        System.out.println("销毁方法......");
    }

    @Override
    public Account queryAccountByCardNo(String cardNo) throws Exception {
     
        //从连接池获取连接
//         Connection con = DruidUtils.getInstance().getConnection();
        // 从当前线程中获取连接池对象
        Connection con = connectionUtils.getCurrentThreadConn();
        String sql = "select * from account where cardNo=?";
        PreparedStatement preparedStatement = con.prepareStatement(sql);
        preparedStatement.setString(1,cardNo);
        ResultSet resultSet = preparedStatement.executeQuery();

        Account account = new Account();
        while(resultSet.next()) {
     
            account.setCardNo(resultSet.getString("cardNo"));
            account.setName(resultSet.getString("name"));
            account.setMoney(resultSet.getInt("money"));
        }

        resultSet.close();
        preparedStatement.close();
//        con.close(); // 不能将当前线程的连接关闭了，不然同个线程同个业务中其他更新方法获取的连接就不是同一个

        return account;
    }

    @Override
    public int updateAccountByCardNo(Account account) throws Exception {
     

        // 从连接池获取连接
        // 改造为：从当前线程当中获取绑定的connection连接
//        Connection con = DruidUtils.getInstance().getConnection();
        // 从当前线程中获取连接池对象
        Connection con = connectionUtils.getCurrentThreadConn();
        String sql = "update account set money=? where cardNo=?";
        PreparedStatement preparedStatement = con.prepareStatement(sql);
        preparedStatement.setInt(1,account.getMoney());
        preparedStatement.setString(2,account.getCardNo());
        int i = preparedStatement.executeUpdate();

        preparedStatement.close();
//        con.close();
        return i;
    }
}

2.5.7.service层

• TransferService

package com.lagou.edu.service;


public interface TransferService {
     

    void transfer(String fromCardNo,String toCardNo,int money) throws Exception;
}

• TransferServiceImpl

package com.lagou.edu.service.impl;

import com.lagou.edu.dao.AccountDao;
import com.lagou.edu.pojo.Account;
import com.lagou.edu.service.TransferService;
import com.lagou.edu.utils.TransactionManager;


public class TransferServiceImpl implements TransferService {
     

//    private AccountDao accountDao = new JdbcAccountDaoImpl();

//     private AccountDao accountDao = (AccountDao) BeanFactory.getBean("accountDao");

    // 最佳状态
    private AccountDao accountDao;

    // 构造函数传值/set方法传值

    public void setAccountDao(AccountDao accountDao) {
     
        this.accountDao = accountDao;
    }



    @Override
    public void transfer(String fromCardNo, String toCardNo, int money) throws Exception {
     

//        try {
     
//            // 开启事务（设置自动提交关闭）
//            TransactionManager.getInstance().beginTranscation();
            Account from = accountDao.queryAccountByCardNo(fromCardNo);
            Account to = accountDao.queryAccountByCardNo(toCardNo);

            from.setMoney(from.getMoney()-money);
            to.setMoney(to.getMoney()+money);

            accountDao.updateAccountByCardNo(to);
            int c = 1/0;
            accountDao.updateAccountByCardNo(from);
            // 事务提交
//            TransactionManager.getInstance().commit();
//        }catch (Exception e){
     
//            // 事务回滚
//            TransactionManager.getInstance().rollback();
//            throw e;
//        }


    }
}

2.5.8.controller层

• TransferServlet

package com.lagou.edu.servlet;

import com.lagou.edu.factory.BeanFactory;
import com.lagou.edu.factory.ProxyFactory;
import com.lagou.edu.service.impl.TransferServiceImpl;
import com.lagou.edu.utils.JsonUtils;
import com.lagou.edu.pojo.Result;
import com.lagou.edu.service.TransferService;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;


@WebServlet(name="transferServlet",urlPatterns = "/transferServlet")
public class TransferServlet extends HttpServlet {
     

    // 1. 实例化service层对象
//    private TransferService transferService = new TransferServiceImpl();
//    private TransferService transferService = (TransferService) BeanFactory.getBean("transferService");

    // 从工厂获取委托对象，使用代理对象，主要增加了事务控制
    private ProxyFactory proxyFactory = (ProxyFactory) BeanFactory.getBean("proxyFactory");
    private TransferService transferService = (TransferService) proxyFactory.getJdkProxy((TransferService) BeanFactory.getBean("transferService"));

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
     

        // 设置请求体的字符编码
        req.setCharacterEncoding("UTF-8");

        String fromCardNo = req.getParameter("fromCardNo");
        String toCardNo = req.getParameter("toCardNo");
        String moneyStr = req.getParameter("money");
        int money = Integer.parseInt(moneyStr);

        Result result = new Result();

        try {
     

            // 2. 调用service层方法
            transferService.transfer(fromCardNo,toCardNo,money);
            result.setStatus("200");
        } catch (Exception e) {
     
            e.printStackTrace();
            result.setStatus("201");
            result.setMessage(e.toString());
        }

        // 响应
        resp.setContentType("application/json;charset=utf-8");
        resp.getWriter().print(JsonUtils.object2Json(result));
    }
}

2.5.9.注意事项

com.lagou.edu.utils.ConnectionUtils#getCurrentThreadConn中一定要注意，第一次获取连接为空时，创建连接后要设置到当前线程中。

 if (connection == null){
     
            connection = DruidUtils.getInstance().getConnection();
            // 创建完成后一定要设置回去
            threadLocal.set(connection);
        }

文章内容输出来源：拉勾教育Java高薪训练营