mybatis逆向工程与分页在springboot中的应用及遇到坑

最近在项目中应用到springboot与mybatis，在进行整合过程中遇到一些坑，在此将其整理出来，便于以后查阅与复习。

项目运行环境为：eclispe+jdk1.8+maven

搭建Spring Boot环境

首先建立maven project,在生成的pom文件中加入依赖，代码如下：

<parent>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-parent</artifactId>
 <version>1.5.2.RELEASE</version>
 <relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
 <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
 <java.version>1.8</java.version>
</properties>
<dependencies>
 <dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
 </dependency>
 <dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-test</artifactId>
 </dependency>
 <dependency>
  <groupId>org.mybatis.spring.boot</groupId>
  <artifactId>mybatis-spring-boot-starter</artifactId>
  <version>1.3.0</version>
 </dependency>
 <dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <scope>runtime</scope>
 </dependency>
 <!--分页插件-->
 <dependency>
   <groupId>com.github.pagehelper</groupId>
   <artifactId>pagehelper-spring-boot-starter</artifactId>
   <version>1.2.1</version>
 </dependency>
 <!-- alibaba的druid数据库连接池 -->
 <dependency>
  <groupId>com.alibaba</groupId>
  <artifactId>druid</artifactId>
  <version>1.0.29</version>
 </dependency>
</dependencies>
<build>
 <plugins>
  <plugin>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-maven-plugin</artifactId>
  </plugin>
  <!-- mybatis generator 自动生成代码插件 -->
  <plugin>
   <groupId>org.mybatis.generator</groupId>
   <artifactId>mybatis-generator-maven-plugin</artifactId>
   <version>1.3.2</version>
   <configuration>
    <configurationFile>${basedir}/src/main/resources/generator/generatorConfig.xml</configurationFile>
    <overwrite>true</overwrite>
    <verbose>true</verbose>
   </configuration>
  </plugin>
 </plugins>
</build>

配置好依赖后进行maven install,此时注意的坑：

坑一：启动maven install报错：

[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage (default) on project springboot-mybatis: Execution default of goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage failed: Unable to find main class -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException

报错原因是没有启动类

解决方法:编写启动类Main.java正常运行！

@SpringBootApplication
public class Main {
 public static void main(String[] args) {
  SpringApplication.run(Main.class, args);
 }
}

坑二：启动maven install报错：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project springboot-mybatis: Compilation failure
[ERROR] No compiler is provided in this environment. Perhaps you are running on a JRE rather than a JDK?
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

报错原因：项目的java环境与电脑环境不符合，例如我的新建项目运行环境为J2SE-1.5,报错是在我将其改为jre1.8之后

 解决方案：

右键项目——build path——Configure build path——Libraries——双击Jre System Libraries如下图所示：

选择Alternate JRE 如2处的下拉框只有jre，点击3处的Install JREs，依次经过add——Standard VM——next——Directory,选择本机的jdk位置点击finish

在install JREs位置将默认勾选更改jdk,如下图所示，并保存。

再次maven install项目正常。如下所示：

[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.351 s
[INFO] Finished at: 2018-09-05T21:20:48+08:00
[INFO] Final Memory: 23M/181M
[INFO] ------------------------------------------------------------------------

在src/main/resources新建文件：application.yml，内容如下所示：

server:
 port: 8080
spring:
 datasource:
  name: test
  url: jdbc:mysql://localhost:3306/test
  username: root
  password: 123456
  driver-class-name: com.mysql.jdbc.Driver
## 该配置节点为独立的节点
mybatis:
 mapper-locations: classpath:mapper/*.xml
#pagehelper分页插件
pagehelper:
 helperDialect: mysql
 reasonable: true
 supportMethodsArguments: true
 params: count=countSql

至此springboot环境搭建完毕！

逆向工程应用

首先应该注意到在pom文件中有配置逆向工程xml文件的位置：src/main/resources/generator/generatorConfig.xml

因而在src/main/resources下新建generator文件夹，并建立generatorConfig.xml文件，代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN" "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
 <!-- 数据库驱动:选择你的本地硬盘上面的数据库驱动包-->
 <classPathEntry location="E:\plugins\maven\repo\mysql\mysql-connector-java\5.1.41\mysql-connector-java-5.1.41.jar"/>
 <context id="DB2Tables" targetRuntime="MyBatis3">
  <commentGenerator>
   <property name="suppressDate" value="true"/>
   <!-- 是否去除自动生成的注释 true：是 ： false:否 -->
   <property name="suppressAllComments" value="true"/>
  </commentGenerator>
  <!--数据库链接URL，用户名、密码 -->
  <jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://localhost/test" userId="root" password="123456">
  </jdbcConnection>
  <javaTypeResolver>
   <property name="forceBigDecimals" value="false"/>
  </javaTypeResolver>
  <!-- 生成pojo类的位置-->
  <javaModelGenerator targetPackage="com.luis.entity" targetProject="src/main/java">
   <property name="enableSubPackages" value="true"/>
   <property name="trimStrings" value="true"/>
  </javaModelGenerator>
  <!-- 生成映射文件的包名和位置-->
  <sqlMapGenerator targetPackage="mapper" targetProject="src/main/resources">
   <!-- enableSubPackages 是否让schema作为包的后缀-->
   <property name="enableSubPackages" value="false"/>
  </sqlMapGenerator>
  <!-- 生成mapper接口的位置-->
  <javaClientGenerator type="XMLMAPPER" targetPackage="com.luis.mapper" targetProject="src/main/java">
   <!-- enableSubPackages 是否让schema作为包的后缀-->
   <property name="enableSubPackages" value="false"/>
  </javaClientGenerator>
  <!-- 指定数据库表 -->
  <table schema="" tableName="user"></table>
 </context>
</generatorConfiguration>

根据个人环境将配置文件中的配置进行更改，如数据库密码，包名，对应数据库表

所用的数据库表如下：

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
 `id` bigint(20) NOT NULL,
 `name` varchar(255) NOT NULL,
 `age` int(4) NOT NULL,
 PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `user` VALUES ('1', 'wanger', '22');
INSERT INTO `user` VALUES ('2', 'zhangsan', '18');
INSERT INTO `user` VALUES ('3', 'lisi', '23');
INSERT INTO `user` VALUES ('4', 'wangwu', '21');

配置完成后，右键项目，选择run as——Maven build——在下面两处分别填入：

Goals: mybatis-generator:generate -e
 Profiles: generatorConfig.xml

如下图所示：

出现如下所示，代码生成成功，刷新项目即可。

[INFO] Generating Example class for table user
[INFO] Generating Record class for table user
[INFO] Generating Mapper Interface for table user
[INFO] Generating SQL Map for table user
[INFO] Saving file UserMapper.xml
[INFO] Saving file UserExample.java
[INFO] Saving file User.java
[INFO] Saving file UserMapper.java
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

需要注意的是：逆向工程生成的代码不会覆盖，因而不能重复多次生成。

此处也有个小坑，逆向工程的代码生成后，启动项目会报如下错误：

***************************
APPLICATION FAILED TO START
***************************

Description:

Field userMapper in com.luis.service.impl.UserServiceImpl required a bean of type 'com.luis.mapper.UserMapper' that could not be found.

Action:

Consider defining a bean of type 'com.luis.mapper.UserMapper' in your configuration.

解决方案：

1、给生成的mapper接口文件前加注解：@Mapper 即可解决。但需要给每一个mapper文件前加，繁琐，因而有第二种类

解决办法

2、在启动类前加@MapperScan({"com.luis.mapper"})，其中com.luis.mapper为mapper文件的所在位置。

参考自：http://412887952-qq-com.iteye.com/blog/2392672

分页应用

逆向工程已经生成了entity类，及dao层的mapper接口与*mapper.xml文件，因而/只用编写service层与web层。

首先在UserService中编写接口，代码如下：

public interface UserService {
 User selectByName(String name);
 List<User> findAllUser(int pageNum, int pageSize);
}

在UserServiceImpl文件进行实现，代码如下所示：

@Service
public class UserServiceImpl implements UserService {
 @Autowired
 private UserMapper userMapper;
 @Override
 public User selectByName(String name) {
  UserExample example = new UserExample();
  Criteria criteria = example.createCriteria();
  criteria.andNameEqualTo(name);
  List<User> users = userMapper.selectByExample(example);
  if (users != null && users.size() > 0) {
   return users.get(0);
  }
  return null;
 }
 /**
  * pageNum 开始页数
  * pageSize 每页显示的数据条数
  */
 @Override
 public List<User> findAllUser(int pageNum, int pageSize) {
  //将参数传给方法实现分页
  PageHelper.startPage(pageNum, pageSize);
  UserExample example = new UserExample();
  List<User> list = userMapper.selectByExample(example);
  return list;
 }
}

最后在controller层对查询结果进行接收，UserController代码如下：

@Controller
@RestController
public class UserController {
 @Autowired
 private UserService userService;
 @RequestMapping("/test")
 public User querUserByName() {
  User user = userService.selectByName("luis");
  System.out.println(user.toString());
  return user;
 }
 @RequestMapping("/list")
 public List<User> querUser() {
  List<User> list = userService.findAllUser(1, 2);
  //获取分页信息
  PageInfo<User> pageInfo = new PageInfo<>(list);
  System.out.println("total:" + pageInfo.getTotal());
  System.out.println("pages:" + pageInfo.getPages());
  System.out.println("pageSize:" + pageInfo.getPageSize());
  return list;
 }
}

测试

此前在项目编写过程中已经对可能出现的错误进行了总结，最后，对项目的功能进行测试，通过加@RestController注解将数据传输到浏览器中。

测试mybatis与springboot，浏览器输入http://localhost:8080/test，浏览器输出：

{"id":1,"name":"wanger","age":22}

分页测试，浏览器输入http://localhost:8080/list，浏览器输出：

[{"id":1,"name":"wanger","age":22},{"id":2,"name":"zhangsan","age":18}]

eclipse输出：

total:4
pages:2
pageSize:2

项目搭建完毕，具体代码参见github

总结

以上所述是小编给大家介绍的mybatis逆向工程与分页在springboot中的应用，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对我们网站的支持！