上一篇文章，写了如何搭建一个简单的Spring boot项目，本篇是接着上一篇文章写得：Spring boot入门：快速搭建Spring boot项目（一），主要是spring boot集成mybatis和pagehelper
关于mybatis和pagehelper的介绍，可以自行博客，网上很多类似的博客，这里，我直接上代码和项目搭建教程。
1.配置文件：在配置文件application.yml中配置MySql数据库连接池和Mybatis扫描包以及PageHelper分页插件
mybatis:
mapper-locations: classpath:mapper/*.xml
type-aliases-package: com.tswc.edu.entity mapper:
mappers:
- com.tswc.edu.util.MyMapper
not-empty: false
identity: MYSQL
#identity: SQLSERVER pagehelper:
helperDialect: MYSQL
reasonable: true
supportMethodsArguments: true
params: count=countSql spring:
datasource:
type: com.alibaba.druid.pool.DruidDataSource
driverClassName: com.mysql.jdbc.Driver
url: jdbc:mysql://127.0.0.1:3306/edu?useUnicode=true&characterEncoding=utf8
username: root
password: 123456
initialSize: 1
minIdle: 3
maxActive: 20
# 配置获取连接等待超时的时间
maxWait: 60000
# 配置间隔多久才进行一次检测，检测需要关闭的空闲连接，单位是毫秒
timeBetweenEvictionRunsMillis: 60000
# 配置一个连接在池中最小生存的时间，单位是毫秒
minEvictableIdleTimeMillis: 30000
validationQuery: select 'x'
testWhileIdle: true
testOnBorrow: false
testOnReturn: false
# 打开PSCache，并且指定每个连接上PSCache的大小
poolPreparedStatements: true
maxPoolPreparedStatementPerConnectionSize: 20
# 配置监控统计拦截的filters，去掉后监控界面sql无法统计，'wall'用于防火墙
filters: stat,wall,slf4j
# 通过connectProperties属性来打开mergeSql功能；慢SQL记录
connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000
# 合并多个DruidDataSource的监控数据
#useGlobalDataSourceStat: true
同时，需要在pom.xml中添加相应的jar包依赖,如果存在jar包无法下载，可以手动下载，然后放到相应的jar包文件夹中
***********************************这里面需要注意Spring boot和mybatis的jar包之间的版本，sping boot2+要求高版本，eg：spring boot2+不能识别pagehelper1.2以下的版本
<!--mybatis -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.6</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.4.4</version>
</dependency> <dependency>
<groupId>org.mybatis.spring.boot</groupId>
<artifactId>mybatis-spring-boot-starter</artifactId>
<version>1.1.1</version>
</dependency>
<!--druid -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.0.28</version>
</dependency> <!--mapper-->
<dependency>
<groupId>tk.mybatis</groupId>
<artifactId>mapper-spring-boot-starter</artifactId>
<version>2.1.0</version>
</dependency>
<!--pagehelper,Spring boot2.0+只能设备pagehelper1.2+-->
<dependency>
<groupId>com.github.pagehelper</groupId>
<artifactId>pagehelper-spring-boot-starter</artifactId>
<version>1.2.5</version>
</dependency>
2：代码部分
（1）.更新入口主文件，主要增加了一些注解，
此处需要注意@MapperSca的引用，这里有2个可引用的包，分别是tk.mybatis.spring.annotation.MapperScan和org.mybatis.spring.annotation.MapperScan;
tk.mybatis.spring.annotation.MapperScan：为mubatis带的mapper扫描文件，org.mybatis.spring.annotation.MapperScan为spring自带的扫描文件，在低版本的mybatis上，2个包可以随意使用，但是Spring boot2+后，增加了一些特性（建议阅读spring boot2+的底层代码，加深理解），导致只能使用高版本的mtbatis，同时spring自带的MapperScan也无法使用，所以使用sping boot2+后，需要引用高版本的mybatis，同时这里只能使用mybatis的MapperScan的扫描包；spring在后期更新中，应该也会使其能够用于boot中
@ServletComponentScan
@MapperScan(basePackages = "com.tswc.edu.mapper")
@SpringBootApplication
public class EduApplication { public static void main(String[] args) {
SpringApplication.run(EduApplication.class, args);
} }
如果在项目正常，启动，但是在使用mybatis时，报此类错误：
后台错误：无法获取实体类对应的表名!
2018-12-14 20:09:25.967 ERROR 29024 --- [nio-8085-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is tk.mybatis.mapper.MapperException: 无法获取实体类com.tswc.edu.entity.Index对应的表名!] with root caus
tk.mybatis.mapper.MapperException: 无法获取实体类com.tswc.edu.entity.Index对应的表名!
at tk.mybatis.mapper.mapperhelper.EntityHelper.getEntityTable(EntityHelper.java:69) ~[mapper-core-1.1.0.jar:na]
at tk.mybatis.mapper.entity.Example.<init>(Example.java:103) ~[mapper-core-1.1.0.jar:na]
at tk.mybatis.mapper.entity.Example.<init>(Example.java:88) ~[mapper-core-1.1.0.jar:na]
at tk.mybatis.mapper.entity.Example.<init>(Example.java:78) ~[mapper-core-1.1.0.jar:na]
at com.tswc.edu.service.IndexService.getList(IndexService.java:33) ~[classes/:na]
at com.tswc.edu.controller.IndexController.list(IndexController.java:35) ~[classes/:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_151]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_151]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_151]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_151]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.13.jar:9.0.13]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) ~[tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:791) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1417) [tomcat-embed-core-9.0.13.jar:9.0.13]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.13.jar:9.0.13]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_151]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_151]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.13.jar:9.0.13]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_151]
前端错误是500
Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback. Fri Dec 14 20:09:25 CST 2018
There was an unexpected error (type=Internal Server Error, status=500).
???????com.tswc.edu.entity.Index?????!
那么，就是Mapper扫描包使用有误
（2）.通用接口mapper：此接口不能被扫描到，否则会报错，可以在application.yml中，排除此包的扫描
public interface MyMapper<T> extends Mapper<T> {
//TODO
//FIXME 特别注意，该接口不能被扫描到，否则会出错
}（3）后台代码，控制村层>服务层>接口
@Controller
public class IndexController {
@Autowired
private IndexService indexService; @RequestMapping(value = "/index")
public void list(ModelMap modelMap) {
List<Index> list = indexService.getList();
modelMap.put("list", list);
}
}
@Service
public class IndexService {
@Autowired
private IndexMapper indexMapper; public List<Index> getList() {
Example example = new Example(Index.class);
example.setTableName("index_test");
Criteria criteria = example.createCriteria();
criteria.andEqualTo("age", 20);
return indexMapper.selectByExample(example);
}
}
public interface IndexMapper extends MyMapper<Index> {
}@Table(name = "index_test")
public class Index implements Serializable, IDynamicTableName {
private static final long serialVersionUID = -8709793124943394842L; @Transient
private String dynamicTableName;
private String name;
private Integer age; public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public Integer getAge() {
return age;
} public void setAge(Integer age) {
this.age = age;
} @Override
public String getDynamicTableName() {
return null;
}
}
最后一个类为实体类，建议在建立实体类的时候，统一加上@Table的注解，方便后期Mybatis的使用，同时也提高了代码的规范性。当然，如果我们使用Mybatis的代码生成器，那么均会自动加上注解（代码生成器在后期的博客中会讲到）
（4）.前端ftl代码
<!DOCTYPE html>
<html>
<head lang="en">
<title>Spring Boot Demo - FreeMarker</title>
<link href="/css/index.css" rel="stylesheet" />
</head>
<body>
<table>
<#list list as user>
<tr>
<td>第${user_index+1}个用户</td>
<td>用户名：${user.name}</td>
<td>年 龄: ${user.age}</td>
</tr>
</#list>
</table>
</body>
</html>
（5）添加mybatis的空配置文件，由于spring boot中，数据库是通过配置文件的形式，所以此文件是空的，但是没有此文件，mybatis就无法通过；当然，也可以通过在此文件作用配置数据库连接池的方式连接数据（已过时）
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD SQL MAP Config 3.1//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<settings>
<setting name="callSettersOnNulls" value="true"/>
</settings>
</configuration>
（6）数据库如下：添加了几条测试数据：
（7）.启动项目，并访问http://localhost:8085/index，结果如下：
最终，项目代码的机构，如下：