Spring boot 入门（二）：Spring boot集成MySql,Mybatis和PageHelper插件
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
1 mybatis: 2 mapper-locations: classpath:mapper/*.xml 3 type-aliases-package: com.tswc.edu.entity 4 5 mapper: 6 mappers: 7 - com.tswc.edu.util.MyMapper 8 not-empty: false 9 identity: MYSQL 10 #identity: SQLSERVER 11 12 pagehelper: 13 helperDialect: MYSQL 14 reasonable: true 15 supportMethodsArguments: true 16 params: count=countSql 17 18 spring: 19 datasource: 20 type: com.alibaba.druid.pool.DruidDataSource 21 driverClassName: com.mysql.jdbc.Driver 22 url: jdbc:mysql://127.0.0.1:3306/edu?useUnicode=true&characterEncoding=utf8 23 username: root 24 password: 123456 25 initialSize: 1 26 minIdle: 3 27 maxActive: 20 28 # 配置获取连接等待超时的时间 29 maxWait: 60000 30 # 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 31 timeBetweenEvictionRunsMillis: 60000 32 # 配置一个连接在池中最小生存的时间，单位是毫秒 33 minEvictableIdleTimeMillis: 30000 34 validationQuery: select 'x' 35 testWhileIdle: true 36 testOnBorrow: false 37 testOnReturn: false 38 # 打开PSCache，并且指定每个连接上PSCache的大小 39 poolPreparedStatements: true 40 maxPoolPreparedStatementPerConnectionSize: 20 41 # 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 42 filters: stat,wall,slf4j 43 # 通过connectProperties属性来打开mergeSql功能；慢SQL记录 44 connectionProperties: druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000 45 # 合并多个DruidDataSource的监控数据 46 #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
1 <!--mybatis --> 2 <dependency> 3 <groupId>mysql</groupId> 4 <artifactId>mysql-connector-java</artifactId> 5 <version>5.1.6</version> 6 </dependency> 7 <dependency> 8 <groupId>org.mybatis</groupId> 9 <artifactId>mybatis</artifactId> 10 <version>3.4.4</version> 11 </dependency> 12 13 <dependency> 14 <groupId>org.mybatis.spring.boot</groupId> 15 <artifactId>mybatis-spring-boot-starter</artifactId> 16 <version>1.1.1</version> 17 </dependency> 18 <!--druid --> 19 <dependency> 20 <groupId>com.alibaba</groupId> 21 <artifactId>druid</artifactId> 22 <version>1.0.28</version> 23 </dependency> 24 25 <!--mapper--> 26 <dependency> 27 <groupId>tk.mybatis</groupId> 28 <artifactId>mapper-spring-boot-starter</artifactId> 29 <version>2.1.0</version> 30 </dependency> 31 <!--pagehelper,Spring boot2.0+只能设备pagehelper1.2+--> 32 <dependency> 33 <groupId>com.github.pagehelper</groupId> 34 <artifactId>pagehelper-spring-boot-starter</artifactId> 35 <version>1.2.5</version> 36 </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
1 @ServletComponentScan 2 @MapperScan(basePackages = "com.tswc.edu.mapper") 3 @SpringBootApplication 4 public class EduApplication { 5 6 public static void main(String[] args) { 7 SpringApplication.run(EduApplication.class, args); 8 } 9 10 }
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!
1 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 2 3 tk.mybatis.mapper.MapperException: 无法获取实体类com.tswc.edu.entity.Index对应的表名! 4 at tk.mybatis.mapper.mapperhelper.EntityHelper.getEntityTable(EntityHelper.java:69) ~[mapper-core-1.1.0.jar:na] 5 at tk.mybatis.mapper.entity.Example.<init>(Example.java:103) ~[mapper-core-1.1.0.jar:na] 6 at tk.mybatis.mapper.entity.Example.<init>(Example.java:88) ~[mapper-core-1.1.0.jar:na] 7 at tk.mybatis.mapper.entity.Example.<init>(Example.java:78) ~[mapper-core-1.1.0.jar:na] 8 at com.tswc.edu.service.IndexService.getList(IndexService.java:33) ~[classes/:na] 9 at com.tswc.edu.controller.IndexController.list(IndexController.java:35) ~[classes/:na] 10 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_151] 11 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_151] 12 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_151] 13 at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_151] 14 at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:189) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 15 at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 16 at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:102) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 17 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 18 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:800) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 19 at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 20 at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1038) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 21 at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 22 at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 23 at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:897) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 24 at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 25 at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882) ~[spring-webmvc-5.1.3.RELEASE.jar:5.1.3.RELEASE] 26 at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 27 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 28 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 29 at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.13.jar:9.0.13] 30 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 31 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 32 at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 33 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 34 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 35 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 36 at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:92) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 37 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 38 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 39 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 40 at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:93) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 41 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 42 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 43 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 44 at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:200) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 45 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-5.1.3.RELEASE.jar:5.1.3.RELEASE] 46 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 47 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 48 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) ~[tomcat-embed-core-9.0.13.jar:9.0.13] 49 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) [tomcat-embed-core-9.0.13.jar:9.0.13] 50 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490) [tomcat-embed-core-9.0.13.jar:9.0.13] 51 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) [tomcat-embed-core-9.0.13.jar:9.0.13] 52 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) [tomcat-embed-core-9.0.13.jar:9.0.13] 53 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) [tomcat-embed-core-9.0.13.jar:9.0.13] 54 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) [tomcat-embed-core-9.0.13.jar:9.0.13] 55 at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408) [tomcat-embed-core-9.0.13.jar:9.0.13] 56 at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-9.0.13.jar:9.0.13] 57 at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:791) [tomcat-embed-core-9.0.13.jar:9.0.13] 58 at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1417) [tomcat-embed-core-9.0.13.jar:9.0.13] 59 at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-9.0.13.jar:9.0.13] 60 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_151] 61 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_151] 62 at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-9.0.13.jar:9.0.13] 63 at java.lang.Thread.run(Thread.java:748) [na:1.8.0_151]
前端错误是500
1 Whitelabel Error Page 2 This application has no explicit mapping for /error, so you are seeing this as a fallback. 3 4 Fri Dec 14 20:09:25 CST 2018 5 There was an unexpected error (type=Internal Server Error, status=500). 6 ???????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
1 public interface MyMapper<T> extends Mapper<T> { 2 //TODO 3 //FIXME 特别注意，该接口不能被扫描到，否则会出错 4 }
（3）后台代码，控制村层>服务层>接口
1 @Controller 2 public class IndexController { 3 @Autowired 4 private IndexService indexService; 5 6 @RequestMapping(value = "/index") 7 public void list(ModelMap modelMap) { 8 List<Index> list = indexService.getList(); 9 modelMap.put("list", list); 10 } 11 }
1 @Service 2 public class IndexService { 3 @Autowired 4 private IndexMapper indexMapper; 5 6 public List<Index> getList() { 7 Example example = new Example(Index.class); 8 example.setTableName("index_test"); 9 Criteria criteria = example.createCriteria(); 10 criteria.andEqualTo("age", 20); 11 return indexMapper.selectByExample(example); 12 } 13 }
1 public interface IndexMapper extends MyMapper<Index> { 2 }
1 @Table(name = "index_test") 2 public class Index implements Serializable, IDynamicTableName { 3 private static final long serialVersionUID = -8709793124943394842L; 4 5 @Transient 6 private String dynamicTableName; 7 private String name; 8 private Integer age; 9 10 public String getName() { 11 return name; 12 } 13 14 public void setName(String name) { 15 this.name = name; 16 } 17 18 public Integer getAge() { 19 return age; 20 } 21 22 public void setAge(Integer age) { 23 this.age = age; 24 } 25 26 @Override 27 public String getDynamicTableName() { 28 return null; 29 } 30 }
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
1 <!DOCTYPE html> 2 <html> 3 <head lang="en"> 4 <title>Spring Boot Demo - FreeMarker</title> 5 <link href="/css/index.css" rel="stylesheet" /> 6 </head> 7 <body> 8 <table> 9 <#list list as user> 10 <tr> 11 <td>第${user_index+1}个用户</td> 12 <td>用户名：${user.name}</td> 13 <td>年 龄: ${user.age}</td> 14 </tr> 15 </#list> 16 </table> 17 </body> 18 </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）
1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD SQL MAP Config 3.1//EN" 3 "http://mybatis.org/dtd/mybatis-3-config.dtd"> 4 <configuration> 5 <settings> 6 <setting name="callSettersOnNulls" value="true"/> 7 </settings> 8 </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：
