前言

如果看过前几篇文章，对 Spring 和 MyBatis 有了一定了解，一定想上手试试。这篇文章从 0 到 1，手把手整合 SSM (Spring、Spring MVC、MyBatis)。

本篇是代码篇，在 PC 端浏览更佳，源码在文末

搭建整合 SSM 之 HelloWorld

开发环境

• idea
• MySql5.x
• jdk8
• maven

对应的技术入门在 公众号 历史文章 都可以找到

目录

目录包括 main、resources、mapper、webapp，不一一介绍，不熟悉查看前面文章。

环境搭建

新建项目

这里使用的是 IDEA 编辑器，新建一个 Maven 工程，选择 web 项目。

导入依赖

使用 Maven 管理项目 jar ，只需要在 pom.xml 加如相关依赖即可。

<?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><groupId>javapub.rodert.github</groupId><artifactId>ssm_helloword_web</artifactId><version>1.0-SNAPSHOT</version><packaging>war</packaging><url></url>
<!--    源码：https://github.com/Rodert/JavaPub--><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><spring.version>4.3.6.RELEASE</spring.version></properties><dependencies><!-- 单元测试 --><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>4.12</version></dependency><!-- 1.日志 --><!-- 实现slf4j接口并整合 --><dependency><groupId>ch.qos.logback</groupId><artifactId>logback-classic</artifactId><version>1.1.1</version></dependency><!-- 2.数据库 --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.37</version><scope>runtime</scope></dependency><dependency><groupId>c3p0</groupId><artifactId>c3p0</artifactId><version>0.9.1.2</version></dependency><!-- DAO: MyBatis --><dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.3.0</version></dependency><dependency><groupId>org.mybatis</groupId><artifactId>mybatis-spring</artifactId><version>1.2.3</version></dependency><!-- 3.Servlet web --><dependency><groupId>taglibs</groupId><artifactId>standard</artifactId><version>1.1.2</version></dependency><dependency><groupId>jstl</groupId><artifactId>jstl</artifactId><version>1.2</version></dependency><dependency><groupId>com.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.5.4</version></dependency><dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version></dependency><!-- 4.Spring --><!-- 1)Spring核心 --><dependency><groupId>org.springframework</groupId><artifactId>spring-core</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>${spring.version}</version></dependency><!-- 2)Spring DAO层 --><dependency><groupId>org.springframework</groupId><artifactId>spring-jdbc</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-tx</artifactId><version>${spring.version}</version></dependency><!-- 3)Spring web --><dependency><groupId>org.springframework</groupId><artifactId>spring-web</artifactId><version>${spring.version}</version></dependency><dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>${spring.version}</version></dependency><!-- 4)Spring test --><dependency><groupId>org.springframework</groupId><artifactId>spring-test</artifactId><version>${spring.version}</version></dependency><!-- redis客户端:Jedis --><dependency><groupId>redis.clients</groupId><artifactId>jedis</artifactId><version>2.7.3</version></dependency><dependency><groupId>com.dyuproject.protostuff</groupId><artifactId>protostuff-core</artifactId><version>1.0.8</version></dependency><dependency><groupId>com.dyuproject.protostuff</groupId><artifactId>protostuff-runtime</artifactId><version>1.0.8</version></dependency><!-- Map工具类 --><dependency><groupId>commons-collections</groupId><artifactId>commons-collections</artifactId><version>3.2</version></dependency><!--注解--><!-- https://mvnrepository.com/artifact/org.projectlombok/lombok --><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>1.18.12</version><scope>provided</scope></dependency></dependencies><build><finalName>ssm_helloword_web</finalName><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration><source>7</source><target>7</target></configuration></plugin></plugins></build></project>
<!--    源码：https://github.com/Rodert/JavaPub-->

编码

配置文件

spring-dao.xml

• 先在spring文件夹里新建spring-dao.xml文件，我们这里分三层，分别是dao service web。

1. 加载数据库配置
2. 配置数据库连接池
3. 配置 SqlSessionFactory 对象（MyBatis）
4. 配置扫描 dao 层接口，动态代理实现 Dao 实现类，执行 sql 写在 xml

<?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:context="http://www.springframework.org/schema/context"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd"><!-- 配置整合mybatis过程 --><!-- 1.配置数据库相关参数properties的属性：${url} --><context:property-placeholder location="classpath:jdbc.properties" /><!-- 2.数据库连接池 --><bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"><!-- 配置连接池属性 --><property name="driverClass" value="${jdbc.driver}" /><property name="jdbcUrl" value="${jdbc.url}" /><property name="user" value="${jdbc.username}" /><property name="password" value="${jdbc.password}" /><!-- c3p0连接池的私有属性 --><property name="maxPoolSize" value="30" /><property name="minPoolSize" value="10" /><!-- 关闭连接后不自动commit --><property name="autoCommitOnClose" value="false" /><!-- 获取连接超时时间 --><property name="checkoutTimeout" value="10000" /><!-- 当获取连接失败重试次数 --><property name="acquireRetryAttempts" value="2" /></bean><!-- 3.配置SqlSessionFactory对象 --><bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"><!-- 注入数据库连接池 --><property name="dataSource" ref="dataSource" /><!-- 配置MyBaties全局配置文件:mybatis-config.xml --><property name="configLocation" value="classpath:Mybatis-config.xml" /><!-- 扫描entity包 使用别名 --><property name="typeAliasesPackage" value="javapub.rodert.github.entity" /><!-- 扫描sql配置文件:mapper需要的xml文件 --><property name="mapperLocations" value="classpath:mapper/*.xml" /></bean><!-- 4.配置扫描Dao接口包，动态实现Dao接口，注入到spring容器中 --><bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"><!-- 注入sqlSessionFactory --><property name="sqlSessionFactoryBeanName" value="sqlSessionFactory" /><!-- 给出需要扫描Dao接口包 --><property name="basePackage" value="javapub.rodert.github.dao" /></bean>
</beans>

jdbc.properties

数据库配置，在 resources 文件夹里新建一个 jdbc.properties 文件，注意自己的密码。

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/ssm1?useUnicode=true&characterEncoding=utf8
jdbc.username=root
jdbc.password=

mybatis-config.xml

MyBatis 核心文件，在recources文件夹里新建mybatis-config.xml文件。

1. 使用自增主键
2. 使用列别名
3. 开启驼峰命名转换 create_time -> createTime

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><!-- 配置全局属性 --><settings><!-- 使用jdbc的getGeneratedKeys获取数据库自增主键值 --><setting name="useGeneratedKeys" value="true" /><!-- 使用列别名替换列名 默认:true --><setting name="useColumnLabel" value="true" /><!-- 开启驼峰命名转换:Table{create_time} -> Entity{createTime} --><setting name="mapUnderscoreToCamelCase" value="true" /></settings>
</configuration>

spring-service.xml

在 spring 文件夹里新建 spring-service.xml 文件。

1. 扫描 service 包所有注解 @Service
2. 配置事务管理器，把事务管理交由 spring 来完成
3. 基于注解的 声明式事务，可以直接在方法上 @Transaction

<?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:context="http://www.springframework.org/schema/context"xmlns:tx="http://www.springframework.org/schema/tx"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/txhttp://www.springframework.org/schema/tx/spring-tx.xsd"><!-- 扫描service包下所有使用注解的类型 --><context:component-scan base-package="javapub.rodert.github.service" /><!-- 配置事务管理器 --><bean id="transactionManager"class="org.springframework.jdbc.datasource.DataSourceTransactionManager"><!-- 注入数据库连接池 --><property name="dataSource" ref="dataSource" /></bean><!-- 配置基于注解的声明式事务 --><tx:annotation-driven transaction-manager="transactionManager" />
</beans>

spring-web.xml

web 层，在 spring 文件夹里新建 spring-web.xml 文件。

1. 开启SpringMVC注解模式，可以使用@RequestMapping，@PathVariable，@ResponseBody等
2. 对静态资源处理，如js，css，jpg等
3. 配置jsp 显示ViewResolver，及渲染后的 JSP
4. 扫描web层 @Controller

<?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:context="http://www.springframework.org/schema/context"xmlns:mvc="http://www.springframework.org/schema/mvc"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/mvchttp://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd"><!-- 配置SpringMVC --><!-- 1.开启SpringMVC注解模式 --><!-- 简化配置：(1)自动注册DefaultAnootationHandlerMapping,AnotationMethodHandlerAdapter(2)提供一些列：数据绑定，数字和日期的format @NumberFormat, @DateTimeFormat, xml,json默认读写支持--><mvc:annotation-driven /><!-- 2.静态资源默认servlet配置(1)加入对静态资源的处理：js,gif,png(2)允许使用"/"做整体映射--><mvc:default-servlet-handler/><!-- 3.配置jsp 显示ViewResolver --><bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"><property name="viewClass" value="org.springframework.web.servlet.view.JstlView" />
<!--        <property name="contentType" value="text/html"/>--><property name="prefix" value="/WEB-INF/jsp/" /><property name="suffix" value=".jsp" /></bean><!-- 4.扫描web相关的bean --><context:component-scan base-package="javapub.rodert.github.web" />
</beans>

web.xml

修改 web.xml 文件了，它在 webapp 的 WEB-INF 下。也可以在这里配置过滤器、监听器等。

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"version="3.1" metadata-complete="true"><!-- 如果是用mvn命令生成的xml，需要修改servlet版本为3.1 --><!-- 配置DispatcherServlet --><servlet><servlet-name>dispatcherServlet</servlet-name><servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class><!-- 配置springMVC需要加载的配置文件spring-dao.xml,spring-service.xml,spring-web.xmlMybatis - > spring -> springmvc--><init-param><param-name>contextConfigLocation</param-name><param-value>classpath:spring/spring-*.xml</param-value></init-param><load-on-startup>1</load-on-startup></servlet><servlet-mapping><servlet-name>dispatcherServlet</servlet-name><!-- 默认匹配所有的请求 --><url-pattern>/</url-pattern></servlet-mapping><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list>
</web-app>

日志

配置一些简单的日志，使用 logback ，在 resources 文件夹里新建logback.xml 文件。

<?xml version="1.0" encoding="UTF-8"?>
<configuration debug="true"><appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"><!-- encoders are by default assigned the type ch.qos.logback.classic.encoder.PatternLayoutEncoder --><encoder><pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern></encoder></appender><root level="debug"><appender-ref ref="STDOUT" /></root>
</configuration>

配置说明

以上配置是整合 SSM 的基础配置，目录结构如图所示：

---

SSM实例-图书管理系统

sql

以上部分整个 SSM 框架就已经搭建好了，下面是一个 Demo ，供参考。

新建俩张表，图书表 book 和 预约图书表 appointment，并初始化数据。

/*
Navicat MySQL Data TransferSource Server         : localhost
Source Server Version : 50716
Source Host           : localhost:3306
Source Database       : ssm1Target Server Type    : MYSQL
Target Server Version : 50716
File Encoding         : 65001Date: 2020-07-12 16:50:43
*/SET FOREIGN_KEY_CHECKS=0;-- ----------------------------
-- Table structure for appointment
-- ----------------------------
DROP TABLE IF EXISTS `appointment`;
CREATE TABLE `appointment` (`book_id` bigint(20) NOT NULL COMMENT '图书ID',`student_id` bigint(20) NOT NULL COMMENT '学号',`appoint_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '预约时间',PRIMARY KEY (`book_id`,`student_id`),KEY `idx_appoint_time` (`appoint_time`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='预约图书表';-- ----------------------------
-- Records of appointment
-- ------------------------------ ----------------------------
-- Table structure for book
-- ----------------------------
DROP TABLE IF EXISTS `book`;
CREATE TABLE `book` (`book_id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '图书ID',`name` varchar(100) NOT NULL COMMENT '图书名称',`number` int(11) NOT NULL COMMENT '馆藏数量',PRIMARY KEY (`book_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1004 DEFAULT CHARSET=utf8 COMMENT='图书表';-- ----------------------------
-- Records of book
-- ----------------------------
INSERT INTO `book` VALUES ('2000', 'Java程序设计', '20');
INSERT INTO `book` VALUES ('2001', '数据结构', '7');
INSERT INTO `book` VALUES ('2002', '设计模式', '20');
INSERT INTO `book` VALUES ('2003', '编译原理', '20');

实体

在 entity 包下新建实体 Book 和 Appointment

• Book.java

package javapub.rodert.github.entity;import lombok.Getter;
import lombok.Setter;
import lombok.ToString;/*** @author wangshiyu rodert* @date 2020/7/6 20:58* @description** @Data 注解，简化代码，自动添加get set toSting 方法* @Getter* @Setter* @ToString*/
@Getter
@Setter
@ToString
public class Book {private long bookId;// 图书IDprivate String name;// 图书名称private int number;// 馆藏数量// 省略构造方法，getter和setter方法，toString方法}

• Appointment.java

package javapub.rodert.github.entity;/*** @author wangshiyu rodert* @date 2020/7/6 20:58* @description*/import lombok.Data;
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;import java.util.Date;/*** 预约图书实体* @Data 注解，简化代码，自动添加get set toSting 方法*/
@Data
public class Appointment {private long bookId;// 图书IDprivate long studentId;// 学号private Date appointTime;// 预约时间// 多对一的复合属性private Book book;// 图书实体// 省略构造方法，getter和setter方法，toString方法}

dao接口

在dao包新建接口 BookDao.java 和 Appointment.java

• BookDao.java

package javapub.rodert.github.dao;/*** @author wangshiyu rodert* @date 2020/7/6 21:01* @description*/import javapub.rodert.github.entity.Book;
import org.apache.ibatis.annotations.Param;import java.util.List;public interface BookDao {/*** 通过ID查询单本图书** @param id* @return*/Book queryById(long id);/*** 查询所有图书** @param offset 查询起始位置* @param limit 查询条数* @return*/List<Book> queryAll(@Param("offset") int offset, @Param("limit") int limit);/*** 减少馆藏数量** @param bookId* @return 如果影响行数等于>1，表示更新的记录行数*/int reduceNumber(long bookId);
}

• AppointmentDao.java

package javapub.rodert.github.dao;/*** @author wangshiyu rodert* @date 2020/7/6 21:01* @description*/import javapub.rodert.github.entity.Appointment;
import org.apache.ibatis.annotations.Param;public interface AppointmentDao {/*** 插入预约图书记录** @param bookId* @param studentId* @return 插入的行数*/int insertAppointment(@Param("bookId") long bookId, @Param("studentId") long studentId);/*** 通过主键查询预约图书记录，并且携带图书实体** @param bookId* @param studentId* @return*/Appointment queryByKeyWithBook(@Param("bookId") long bookId, @Param("studentId") long studentId);}

提示：这里为什么要给方法的参数添加 @Param注解呢？是因为该方法有两个或以上的参数，一定要加，不然 mybatis 识别不了。上面的 BookDao 接口的 queryById 方法和 reduceNumber 方法只有一个参数 book_id ，所以可以不用加 @Param 注解。

---

dao接口xml

这里不需要写 dao接口 的实现类，mybatis会帮我们动态实现，上面我们已经在 spring-dao.xml 配置了动态扫描。现在需要编写相应的 mapper。
在 mapper 目录里新建两个文件 BookDao.xml 和 AppointmentDao.xml ，分别对应上面两个dao接口。

• BookDao.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="javapub.rodert.github.dao.BookDao"><!-- 目的：为dao接口方法提供sql语句配置 --><select id="queryById" resultType="Book" parameterType="long"><!-- 具体的sql -->SELECTbook_id,name,numberFROMbookWHEREbook_id = #{bookId}</select><select id="queryAll" resultType="Book">SELECTbook_id,name,numberFROMbookORDER BYbook_idLIMIT #{offset}, #{limit}</select><update id="reduceNumber">UPDATE bookSET number = number - 1WHEREbook_id = #{bookId}AND number > 0</update>
</mapper>

• AppointmentDao.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="javapub.rodert.github.dao.AppointmentDao"><insert id="insertAppointment"><!-- ignore 主键冲突，报错 -->INSERT ignore INTO appointment (book_id, student_id)VALUES (#{bookId}, #{studentId})</insert><select id="queryByKeyWithBook" resultType="Appointment"><!-- 如何告诉MyBatis把结果映射到Appointment同时映射book属性 --><!-- 可以自由控制SQL -->SELECTa.book_id,a.student_id,a.appoint_time,b.book_id "book.book_id",b.`name` "book.name",b.number "book.number"FROMappointment aINNER JOIN book b ON a.book_id = b.book_idWHEREa.book_id = #{bookId}AND a.student_id = #{studentId}</select>
</mapper>

mapper 说明：namespace 是 xml 对应的接口全名，select 和 update 中的 id 对应方法名（唯一），resultType 是返回值类型，parameterType 是参数类型（这个其实可选），#{...} 中填写的是方法的参数

---

dao接口测试

现在的写法是从数据库层向前（web）写，现在测试一下 dao 接口，编写测试类。

因为每次测试都要加载配置文件，所有抽离一个类（BaseTest），每次测试方法都继承它。

• BaseTest.java

package javapub.rodert.github;/*** @author wangshiyu rodert* @date 2020/7/6 21:07* @description*/import org.junit.runner.RunWith;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;/*** 配置spring和junit整合，junit启动时加载springIOC容器 spring-test,junit*/
@RunWith(SpringJUnit4ClassRunner.class)
// 告诉junit spring配置文件
@ContextConfiguration({ "classpath:spring/spring-dao.xml", "classpath:spring/spring-service.xml" })
public class BaseTest {}

新建 BookDaoTest.java 和 AppointmentDaoTest.java 两个 dao 测试文件。

• BookDao.java

package javapub.rodert.github.dao;/*** @author wangshiyu rodert* @date 2020/7/6 21:08* @description*/import javapub.rodert.github.BaseTest;
import javapub.rodert.github.entity.Book;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;import java.util.List;public class BookDaoTest extends BaseTest {@Autowiredprivate BookDao bookDao;@Testpublic void testQueryById() throws Exception {long bookId = 1000;Book book = bookDao.queryById(bookId);System.out.println(book);}@Testpublic void testQueryAll() throws Exception {List<Book> books = bookDao.queryAll(0, 4);for (Book book : books) {System.out.println(book);}}@Testpublic void testReduceNumber() throws Exception {long bookId = 1000;int update = bookDao.reduceNumber(bookId);System.out.println("update=" + update);}}

• AppointmentDaoTest.java

package javapub.rodert.github.dao;/*** @author wangshiyu rodert* @date 2020/7/6 21:18* @description*/import javapub.rodert.github.BaseTest;
import javapub.rodert.github.entity.Appointment;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;public class AppointmentDaoTest extends BaseTest {@Autowiredprivate AppointmentDao appointmentDao;@Testpublic void testInsertAppointment() throws Exception {long bookId = 1000;long studentId = 12345678910L;int insert = appointmentDao.insertAppointment(bookId, studentId);System.out.println("insert=" + insert);}@Testpublic void testQueryByKeyWithBook() throws Exception {long bookId = 1000;long studentId = 12345678910L;Appointment appointment = appointmentDao.queryByKeyWithBook(bookId, studentId);System.out.println(appointment);System.out.println(appointment.getBook());}}

• BookDaoTest.java – > testQueryById()

测试方法都验证过，没有问题，不一一测试了

---

业务层-结果集封装

到这里，我们的 dao 层，及数据库接口操作都没有问题，下面开始业务层编写。

如果你有实战项目经验，那一定会发现，对于后端接口，我们都会定义一个统一的返回格式，及定义一个返回标准方便前端解析，如下：

{"code":200,"message":"成功","result":{},"isSuccess":true
}

开始写我们的代码，新建枚举类，用来定义预约业务的数据字典。如果不太明白，先看代码，后面在 JavaPub 微信公众号文章索引中查找对应文章。

新建一个包叫 enums，在里面新建一个枚举类 AppointStateEnum.java。

• AppointStateEnum.java

package javapub.rodert.github.enums;/*** @author wangshiyu rodert* @date 2020/7/6 21:20* @description*//*** 使用枚举表述常量数据字典*/
public enum AppointStateEnum {SUCCESS(1, "预约成功"), NO_NUMBER(0, "库存不足"), REPEAT_APPOINT(-1, "重复预约"), INNER_ERROR(-2, "系统异常");private int state;private String stateInfo;private AppointStateEnum(int state, String stateInfo) {this.state = state;this.stateInfo = stateInfo;}public int getState() {return state;}public String getStateInfo() {return stateInfo;}public static AppointStateEnum stateOf(int index) {for (AppointStateEnum state : values()) {if (state.getState() == index) {return state;}}return null;}}

在 dto 包下新建 AppointExecution.java 用来存储我们执行预约操作的返回结果。

• AppointExecution.java

package javapub.rodert.github.dto;/*** @author wangshiyu rodert* @date 2020/7/7 16:26* @description*/import javapub.rodert.github.entity.Appointment;
import javapub.rodert.github.enums.AppointStateEnum;
import lombok.Data;/*** 封装预约执行后结果*/
@Data
public class AppointExecution {// 图书IDprivate long bookId;// 秒杀预约结果状态private int state;// 状态标识private String stateInfo;// 预约成功对象private Appointment appointment;public AppointExecution() {}// 预约失败的构造器public AppointExecution(long bookId, AppointStateEnum stateEnum) {this.bookId = bookId;this.state = stateEnum.getState();this.stateInfo = stateEnum.getStateInfo();}// 预约成功的构造器public AppointExecution(long bookId, AppointStateEnum stateEnum, Appointment appointment) {this.bookId = bookId;this.state = stateEnum.getState();this.stateInfo = stateEnum.getStateInfo();this.appointment = appointment;}// 省略getter和setter方法，toString方法}

在 exception 包下新建三个文件

NoNumberException.java
RepeatAppointException.java
AppointException.java

预约业务异常类（都需要继承 RuntimeException —运行时异常类），分别是无库存异常、重复预约异常、预约未知错误异常，用于业务层非成功情况下的返回（即成功返回结果，失败抛出异常）。为事务做准备。

• AppointException.java

package javapub.rodert.github.exception;/*** @author wangshiyu rodert* @date 2020/7/7 16:31* @description*//*** 预约业务异常*/
public class AppointException extends RuntimeException {public AppointException(String message) {super(message);}public AppointException(String message, Throwable cause) {super(message, cause);}}

• NoNumberException.java

/*** @author wangshiyu rodert* @date 2020/7/7 16:30* @description*/
package javapub.rodert.github.exception;/*** 库存不足异常*/
public class NoNumberException extends RuntimeException {public NoNumberException(String message) {super(message);}public NoNumberException(String message, Throwable cause) {super(message, cause);}}

• RepeatAppointException.java

/*** @author wangshiyu rodert* @date 2020/7/7 16:31* @description*/
package javapub.rodert.github.exception;/*** 重复预约异常*/
public class RepeatAppointException extends RuntimeException {public RepeatAppointException(String message) {super(message);}public RepeatAppointException(String message, Throwable cause) {super(message, cause);}}

Service 业务接口代码

在service包下新建BookService.java图书业务接口。

• BookService.java

/*** @author wangshiyu rodert* @date 2020/7/7 16:32* @description*/
package javapub.rodert.github.service;import javapub.rodert.github.dto.AppointExecution;
import javapub.rodert.github.entity.Book;import java.util.List;/*** 业务接口：站在"使用者"角度设计接口 三个方面：方法定义粒度，参数，返回类型（return 类型/异常）*/
public interface BookService {/*** 查询一本图书** @param bookId* @return*/Book getById(long bookId);/*** 查询所有图书** @return*/List<Book> getList();/*** 预约图书** @param bookId* @param studentId* @return*/AppointExecution appoint(long bookId, long studentId);}

在 service.impl 包下新建 BookServiceImpl.java 使用 BookService 接口，并实现里面的方法。

• BookServiceImpl.java

/*** @author wangshiyu rodert* @date 2020/7/7 16:39* @description*/
package javapub.rodert.github.service.impl;import javapub.rodert.github.dao.AppointmentDao;
import javapub.rodert.github.dao.BookDao;
import javapub.rodert.github.dto.AppointExecution;
import javapub.rodert.github.entity.Appointment;
import javapub.rodert.github.entity.Book;
import javapub.rodert.github.enums.AppointStateEnum;
import javapub.rodert.github.exception.AppointException;
import javapub.rodert.github.exception.NoNumberException;
import javapub.rodert.github.exception.RepeatAppointException;
import javapub.rodert.github.service.BookService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;import java.util.List;@Service
public class BookServiceImpl implements BookService {private Logger logger = LoggerFactory.getLogger(this.getClass());// 注入Service依赖@Autowiredprivate BookDao bookDao;@Autowiredprivate AppointmentDao appointmentDao;@Overridepublic Book getById(long bookId) {return bookDao.queryById(bookId);}@Overridepublic List<Book> getList() {return bookDao.queryAll(0, 1000);}@Override@Transactional/*** 使用注解控制事务方法的优点：* 1.开发团队达成一致约定，明确标注事务方法的编程风格* 2.保证事务方法的执行时间尽可能短，不要穿插其他网络操作，RPC/HTTP请求或者剥离到事务方法外部* 3.不是所有的方法都需要事务，如只有一条修改操作，只读操作不需要事务控制*/public AppointExecution appoint(long bookId, long studentId) {try {// 减库存int update = bookDao.reduceNumber(bookId);if (update <= 0) {// 库存不足//return new AppointExecution(bookId, AppointStateEnum.NO_NUMBER);//错误写法throw new NoNumberException("no number");// 抛出异常，保证触发事务执行} else {// 执行预约操作int insert = appointmentDao.insertAppointment(bookId, studentId);if (insert <= 0) {// 重复预约//return new AppointExecution(bookId, AppointStateEnum.REPEAT_APPOINT);//错误写法throw new RepeatAppointException("repeat appoint");} else {// 预约成功Appointment appointment = appointmentDao.queryByKeyWithBook(bookId, studentId);return new AppointExecution(bookId, AppointStateEnum.SUCCESS, appointment);}}// 要先于catch Exception异常前先catch住再抛出，不然自定义的异常也会被转换为AppointException，导致控制层无法具体识别是哪个异常} catch (NoNumberException | RepeatAppointException e1) {throw e1;} catch (Exception e) {logger.error(e.getMessage(), e);// 所有编译期异常转换为运行期异常//return new AppointExecution(bookId, AppointStateEnum.INNER_ERROR);//错误写法throw new AppointException("appoint inner error:" + e.getMessage());}}}

实现类使用了我们上边定义的异常方法 RepeatAppointException ，用于业务层非成功情况下的返回（即成功返回结果，失败抛出异常）。触发事务。

---

测试一下业务层代码，这里演示预约图书业务。

• BookServiceImplTest.java

/*** @author wangshiyu rodert* @date 2020/7/7 16:40* @description*/
package javapub.rodert.github.service.impl;import javapub.rodert.github.BaseTest;
import javapub.rodert.github.dto.AppointExecution;
import javapub.rodert.github.service.BookService;
import org.junit.Test;
import org.springframework.beans.factory.annotation.Autowired;public class BookServiceImplTest extends BaseTest {@Autowiredprivate BookService bookService;@Testpublic void testAppoint() throws Exception {long bookId = 1001;long studentId = 12345678910L;AppointExecution execution = bookService.appoint(bookId, studentId);System.out.println(execution);}}

测试结果：

首次执行是“预约成功”，如果再次执行的话，应该会出现“重复预约”，至此，我们所有的后台代码都通过单元测试啦~~ 是不是很开心~

---

咱们还需要在dto包里新建一个封装json返回结果的类Result.java，设计成泛型。

• Result.java

package javapub.rodert.github.dto;/*** @author wangshiyu rodert* @date 2020/7/7 21:00* @description*/import lombok.Data;/*** 封装json对象，所有返回结果都使用它*/
@Data
public class Result<T> {private boolean success;// 是否成功标志private T data;// 成功时返回的数据private String error;// 错误信息public Result() {}// 成功时的构造器public Result(boolean success, T data) {this.success = success;this.data = data;}// 错误时的构造器public Result(boolean success, String error) {this.success = success;this.error = error;}// 省略getter和setter方法 使用注解代替
}

web层

web 层，也就是 controller 层，我们在web包下新建BookController.java文件。

• BookController.java

package javapub.rodert.github.web;/*** @author wangshiyu rodert* @date 2020/7/7 21:05* @description*/import javapub.rodert.github.dto.AppointExecution;
import javapub.rodert.github.dto.Result;
import javapub.rodert.github.entity.Book;
import javapub.rodert.github.enums.AppointStateEnum;
import javapub.rodert.github.exception.NoNumberException;
import javapub.rodert.github.exception.RepeatAppointException;
import javapub.rodert.github.service.BookService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.ModelAndView;import java.util.List;@RestController
@RequestMapping("/book") // url:/模块/资源/{id}/细分 /seckill/list
public class BookController {private Logger logger = LoggerFactory.getLogger(this.getClass());@Autowiredprivate BookService bookService;@RequestMapping(value = "/test")public ModelAndView test(){ModelAndView modelAndView = new ModelAndView();modelAndView.setViewName("book/test");modelAndView.addObject("key","welcome javaPub");return modelAndView;}@RequestMapping(value = "/list", method = RequestMethod.GET)private String list(Model model) {List<Book> list = bookService.getList();model.addAttribute("list", list);// list.jsp + model = ModelAndViewreturn "list";// WEB-INF/jsp/"list".jsp}@RequestMapping(value = "/{bookId}/detail", method = RequestMethod.GET)private String detail(@PathVariable("bookId") Long bookId, Model model) {if (bookId == null) {return "redirect:/book/list";}Book book = bookService.getById(bookId);if (book == null) {return "forward:/book/list";}model.addAttribute("book", book);return "detail";}//ajax json//method = RequestMethod.POST,@RequestMapping(value = "/{bookId}/appoint",  produces = {"application/json; charset=utf-8" })@ResponseBodyprivate Result<AppointExecution> appoint(@PathVariable("bookId") Long bookId, @RequestParam("studentId") Long studentId) {if (studentId == null || studentId.equals("")) {return new Result<>(false, "学号不能为空");}//AppointExecution execution = bookService.appoint(bookId, studentId);//错误写法，不能统一返回，要处理异常（失败）情况AppointExecution execution = null;try {execution = bookService.appoint(bookId, studentId);} catch (NoNumberException e1) {execution = new AppointExecution(bookId, AppointStateEnum.NO_NUMBER);} catch (RepeatAppointException e2) {execution = new AppointExecution(bookId, AppointStateEnum.REPEAT_APPOINT);} catch (Exception e) {execution = new AppointExecution(bookId, AppointStateEnum.INNER_ERROR);}return new Result<AppointExecution>(true, execution);}}

目前大多项目都是前后端分离，我们作为服务端，一般和前端通过接口数据交互（json），像接口方法 appoint ，应该添加 @ResponseBody 注解。
测试 controller --> appoint 方法可以通过 curl ，如：

curl -H “Accept: application/json; charset=utf-8” -d “studentId=1234567890” localhost:8080/book/1003/appoint

运行项目

现在整个项目全部完成，配置tomcat，通过左上角引入 tomcat ，选择我们的项目 ssm。

启动成功后：

这里对前端代码只写较少部分，具体可参考 BookController --> book/test 接口，有需要帮助请留言。

• BookController.java --> book/test

    @RequestMapping(value = "/test")public ModelAndView test(){ModelAndView modelAndView = new ModelAndView();modelAndView.setViewName("book/test");modelAndView.addObject("key","welcome javaPub");return modelAndView;}

• test.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%><!DOCTYPE HTML>
<html>
<head><%@ page isELIgnored="false"%><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0,maximum-scale=1.0,user-scalable=no"/><title>news detail</title></head>
<body class="fn-pd24">
<h1>大家好 ${key}</h1><a href="https://mp.weixin.qq.com/s/kfyRAPnRDp8LLktjgd658Q">JavaPub知识清单</a>
</body>
</html>

通过 ModelAndView 将我们需要渲染的数据存储传输到对应视图，由 Sping MVC 定义好的视图解析器对该对象解析，最后将结果数据显示到指定页面。

完整代码地址：https://github.com/Rodert/JavaPub/code/ssm_helloworld_web/

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