SSM之框架整合

时间 2019-11-16

标签 ssm 框架整合繁體版

原文原文链接

前言

SSM框架，即Spring + Spring MVC + MyBatis的整合框架集，是继SSH后比较主流的Java EE企业级框架，采用标准的MVC模式，项目结构与微软的ASP.NET MVC框架很是类似。本文主要结合Intellij IDEA和Maven实现SSM基础框架的搭建与优化。前端

环境

jdk-1.8.0
tomcat-8.6.8
maven-3.3.9
Intellij IDEA 2016java

建立Maven项目

启动IDEA（IDEA的安装请参考IntelliJ IDEA 安装）。
点击"Create New Project"建立新项目mysql

选择右侧的"Maven"，而后配置"Project SDK"为你本机的Java安装目录，接下来填写项目相关信息，建立一个基本的Maven项目git

项目建立完成后，点击右下角的"Enable Auto-Import"以自动导入相关依赖github

接下来须设置项目的Maven设置（每次新建Maven项目都需从新配置），同时按Ctrl+Alt+S打开设置面板，找到Maven配置界面，将"Maven home directory"修改成本机Maven安装目录web

一个基本的Maven环境已经搭建完成，下面开始整合SSM框架。spring

整合SSM框架

POM.xml

POM是项目对象模型(Project Object Model)的简称,pom.xml是Maven的核心配置文件。一个Maven项目必须包含pom.xml配置文件，文件中包括了与开发者有关的，缺陷跟踪系统，组织与许可，项目的URL，项目依赖，以及其余与这个项目相关的东西。sql

如下是本文项目的pom.xml配置文件：数据库

<?xml version="1.0" encoding="UTF-8"?>
<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>4.0.0</modelVersion>
    <packaging>war</packaging>
    <groupId>com.zkh</groupId>
    <artifactId>ssm</artifactId>
    <version>1.0-SNAPSHOT</version>
    <name>ssm</name>
    <url>http://localhost:8081/ssm</url>

    <build>
        <finalName>ssm</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>1.6</source>
                    <target>1.6</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.tomcat.maven</groupId>
                <artifactId>tomcat7-maven-plugin</artifactId>
                <version>2.2</version>
            </plugin>
            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.2</version>
                <configuration>
                    <verbose>true</verbose>
                    <overwrite>true</overwrite>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <spring.version>4.3.7.RELEASE</spring.version>
        <jackson.version>2.9.0.pr1</jackson.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>3.8.1</version>
            <scope>test</scope>
        </dependency>

        <!-- json -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>${jackson.version}</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-core-lgpl</artifactId>
            <version>1.9.13</version>
        </dependency>
        <dependency>
            <groupId>org.codehaus.jackson</groupId>
            <artifactId>jackson-mapper-lgpl</artifactId>
            <version>1.9.13</version>
        </dependency>

        <!-- mail -->
        <dependency>
            <groupId>com.sun.mail</groupId>
            <artifactId>javax.mail</artifactId>
            <version>1.5.6</version>
        </dependency>

        <!-- log4j -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-api</artifactId>
            <version>2.8.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.8.1</version>
        </dependency>

        <!-- mysql -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>6.0.6</version>
        </dependency>
        <dependency>
            <groupId>com.mchange</groupId>
            <artifactId>mchange-commons-java</artifactId>
            <version>0.2.12</version>
        </dependency>

        <!-- slf4j -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>1.7.24</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.24</version>
        </dependency>

        <!-- mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.2</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-ehcache</artifactId>
            <version>1.0.0</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>1.3.1</version>
        </dependency>

        <!-- spring -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aspects</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-expression</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-tx</artifactId>
            <version>${spring.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- SpringMVC -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- validate -->
        <dependency>
            <groupId>javax.validation</groupId>
            <artifactId>validation-api</artifactId>
            <version>2.0.0.Alpha1</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate.validator</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>6.0.0.Alpha1</version>
        </dependency>

        <!-- servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
            <version>2.5</version>
            <scope>provided</scope>
        </dependency>

        <!-- el -->
        <dependency>
            <groupId>javax.el</groupId>
            <artifactId>javax.el-api</artifactId>
            <version>3.0.1-b04</version>
        </dependency>

        <!-- jstl -->
        <dependency>
            <groupId>org.glassfish.web</groupId>
            <artifactId>jstl-impl</artifactId>
            <version>1.2</version>
        </dependency>

        <!-- druid -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.28</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.28.odps</version>
        </dependency>

        <!-- pagehelper -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
            <version>5.0.0</version>
        </dependency>

        <!--shiro-->
        <dependency>
            <groupId>org.apache.shiro</groupId>
            <artifactId>shiro-core</artifactId>
            <version>1.2.5</version>
        </dependency>
        <dependency>
            <groupId>org.apache.shiro</groupId>
            <artifactId>shiro-web</artifactId>
            <version>1.2.5</version>
        </dependency>
        <dependency>
            <groupId>org.apache.shiro</groupId>
            <artifactId>shiro-spring</artifactId>
            <version>1.2.5</version>
        </dependency>

        <dependency>
            <groupId>aopalliance</groupId>
            <artifactId>aopalliance</artifactId>
            <version>1.0</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.8.10</version>
        </dependency>
        <dependency>
            <groupId>cglib</groupId>
            <artifactId>cglib</artifactId>
            <version>3.2.5</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml</groupId>
            <artifactId>classmate</artifactId>
            <version>1.3.3</version>
        </dependency>
        <dependency>
            <groupId>commons-fileupload</groupId>
            <artifactId>commons-fileupload</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-io</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>commons-logging</groupId>
            <artifactId>commons-logging</artifactId>
            <version>1.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-pool2</artifactId>
            <version>2.4.2</version>
        </dependency>
        <dependency>
            <groupId>org.dom4j</groupId>
            <artifactId>dom4j</artifactId>
            <version>2.0.0</version>
        </dependency>
        <dependency>
            <groupId>org.ehcache.modules</groupId>
            <artifactId>ehcache-core</artifactId>
            <version>3.3.0</version>
        </dependency>
        <dependency>
            <groupId>org.javassist</groupId>
            <artifactId>javassist</artifactId>
            <version>3.22.0-CR1</version>
        </dependency>
        <dependency>
            <groupId>org.jboss.logging</groupId>
            <artifactId>jboss-logging</artifactId>
            <version>3.3.0.Final</version>
        </dependency>
    </dependencies>
</project>

springmvc.xml

SpringMVC配置文件：express

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx.xsd">

    <!-- 注解驱动、校验器 -->
    <mvc:annotation-driven validator="validator"/>

    <!-- 视图解析器  -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <!-- 组件扫描 -->
    <context:component-scan base-package="com.zkh.controller"></context:component-scan>

    <!-- 校验器 -->
    <bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean">
        <property name="providerClass" value="org.hibernate.validator.HibernateValidator" />
        <!-- 指定校验使用的资源文件，默认使用classpath:ValidationMessages.properties -->
        <property name="validationMessageSource" ref="messageSource" />
    </bean>
    <!-- 校验错误信息配置文件 -->
    <bean id="messageSource" class="org.springframework.context.support.ReloadableResourceBundleMessageSource">
        <!-- 资源文件名-->
        <property name="basenames">
            <list>
                <value>classpath:ValidationMessages</value>
            </list>
        </property>
        <!-- 资源文件编码格式 -->
        <property name="fileEncodings" value="utf-8" />
        <!-- 对资源文件内容缓存时间，单位秒 -->
        <property name="cacheSeconds" value="120" />
    </bean>

    <!-- 全局异常处理器 -->
    <bean class="com.zkh.exception.CustomExceptionResolver"></bean>

    <!-- 文件上传 -->
    <bean id="multipartResolver"
          class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!-- 默认编码 -->
        <property name="defaultEncoding" value="utf-8" />
        <!-- 文件大小最大值 -->
        <property name="maxUploadSize" value="10485760000" />
        <!-- 内存中的最大值 -->
        <property name="maxInMemorySize" value="40960" />
    </bean>

    <!-- RESTful下静态资源解析 -->
    <!-- <mvc:resources location="/js/" mapping="/js/**"/>
    <mvc:resources location="/img/" mapping="/img/**"/> -->

    <!-- 拦截器 -->
    <!--<mvc:interceptors>-->
        <!--<mvc:interceptor>-->
            <!--<mvc:mapping path="/**"/>-->
            <!--<mvc:mapping path="/user/**"/>-->
            <!--<bean class="com.zkh.interceptor.LoginInterceptor"></bean>-->
        <!--</mvc:interceptor>-->
    <!--</mvc:interceptors>-->

    <!--避免IE执行AJAX时，返回JSON出现下载文件 -->
    <bean id="mappingJacksonHttpMessageConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
        <property name="supportedMediaTypes">
            <list>
                <value>application/json;charset=UTF-8</value>
            </list>
        </property>
    </bean>
</beans>

applicationContext-dao.xml

数据访问接口层配置文件，包含spring与mybatis的整合配置及数据源配置。这里使用了阿里巴巴的Druid链接池以及开源的分页插件PageHelper，Druid能够说是目前最好的数据库链接池，PageHelper能够简化分页功能开发，关于Druid和PageHelper的完整配置会在后面的文章介绍，固然你也可使用c3p0链接池代替，配置文件里包含c3p0的配置方式。

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx
        http://www.springframework.org/schema/tx/spring-tx.xsd">

    <!--引入数据库配置文件-->
    <context:property-placeholder location="classpath:jdbc.properties"/>

    <!--c3p0链接池-->
    <!--<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">-->
    <!--<property name="driverClass" value="${jdbc.driver}"></property>-->
    <!--<property name="jdbcUrl" value="${jdbc.url}"></property>-->
    <!--<property name="user" value="${jdbc.username}"></property>-->
    <!--<property name="password" value="${jdbc.password}"></property>-->
    <!--</bean>-->

    <!--druid链接池-->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
          init-method="init" destroy-method="close">
        <!-- 数据库驱动 -->
        <property name="driverClassName" value="${jdbc.driver}" />
        <property name="url" value="${jdbc.url}" />
        <property name="username" value="${jdbc.username}" />
        <property name="password" value="${jdbc.password}" />
        <!-- 初始化大小、最小、最大链接数 -->
        <property name="initialSize" value="3" />
        <property name="minIdle" value="3" />
        <property name="maxActive" value="20" />
        <!-- 链接等待超时时间，单位是毫秒 -->
        <property name="maxWait" value="60000" />
        <!-- 配置检测间隔，检测须要关闭的空闲链接 -->
        <property name="timeBetweenEvictionRunsMillis" value="60000" />
        <!-- 一个链接在池中的最小生存时间 -->
        <property name="minEvictableIdleTimeMillis" value="300000" />
        <property name="validationQuery" value="SELECT 'x'" />
        <property name="testWhileIdle" value="true" />
        <property name="testOnBorrow" value="false" />
        <property name="testOnReturn" value="false" />
        <!-- 打开PSCache，指定每一个链接PSCache的大小 -->
        <property name="poolPreparedStatements" value="true" />
        <property name="maxPoolPreparedStatementPerConnectionSize" value="20" />
        <!-- 配置监控统计拦截的filters，关闭后监控界面sql没法统计 -->
        <property name="filters" value="stat" />
    </bean>

    <!--spring和mybatis整合-->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!--mybatis配置文件-->
        <property name="configLocation" value="classpath:mybatis/sqlMapConfig.xml"/>
        <!--mapping路径-->
        <property name="mapperLocations" value="classpath:mapping/*.xml"></property>
        <property name="plugins">
            <array>
                <!--分页插件-->
                <bean class="com.github.pagehelper.PageInterceptor">
                    <property name="properties">
                        <value>
                            helperDialect=mysql
                            reasonable=true
                            supportMethodsArguments=true
                            params=count=countSql
                            autoRuntimeDialect=true
                            pageSizeZero=true
                        </value>
                    </property>
                </bean>
            </array>
        </property>
    </bean>

    <!-- mapper扫描器 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.zkh.dao"></property>
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
    </bean>

</beans>

sqlMapConfig.xml

Mybatis配置文件：

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <!--引入数据库配置文件-->
    <properties resource="jdbc.properties"></properties>

    <settings>
        <!-- 开启延迟加载 -->
        <setting name="lazyLoadingEnabled" value="true"/>
        <setting name="aggressiveLazyLoading" value="false"/>
        <!-- 开启二级缓存 -->
        <setting name="cacheEnabled" value="true"/>
    </settings>

    <!--配置类型别名-->
    <typeAliases>
        <!--引入pojo包-->
        <package name="com.zkh.pojo"/>
    </typeAliases>

</configuration>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
    <display-name>ssm</display-name>

    <welcome-file-list>
        <welcome-file>login.action</welcome-file>
    </welcome-file-list>

    <!-- 前端控制器 -->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring/springmvc.xml</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>*.action</url-pattern>
    </servlet-mapping>

    <!-- RESTful前端控制器 -->
    <!-- <servlet>
        <servlet-name>springmvc_rest</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring/springmvc.xml</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>springmvc_rest</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>-->


    <!-- 监听器 -->
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:spring/applicationContext-*.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

    <!-- 编码过滤器 -->
    <filter>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>utf-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

Mapper和pojo

Mapper文件和pojo实体类能够借助"mybatis-generator"自动生成工具生成，关于mybatis-generator的使用请自行Google。

项目结构

以上只是一些最核心的配置文件说明，完整代码已发布在Github上，地址在本文末尾，最终项目结构效果以下：

Tomcat配置

点击菜单栏Run->Edit Configurations...

在Run面板左上方添加，选择Tomcat Server->Local

接下来配置Name(可随意)、Tomcat安装路径、jre安装路径

而后打开Deployment标签页，配置使当前项目自动打包并添加到服务器中

如今能够运行测试你的WEB项目了，按Shift+F10运行应用，Shift+F9可进行应用调试。

运行效果

总结

以上为最基本的SSM整合框架环境搭建，开发过ASP.NET MVC的同窗可能会有一种似曾相识的感受，由于它们真的太像了。以后会向项目中添加一些插件以提升开发效率及应用性能。

具体代码已发布在Github上，地址：SSM

本文为做者kMacro原创，转载请注明来源：http://www.jianshu.com/p/b6b1ec6b1816。