springboot中mybatis逆向工程与分页的应用

约定不等于承诺〃 2021-09-27 10:14 277阅读 0赞

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/> 
    </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>
    
        
        <dependency>
              <groupId>com.github.pagehelper</groupId>
              <artifactId>pagehelper-spring-boot-starter</artifactId>
              <version>1.2.1</version>
        </dependency>
    
        
        <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>
            
            <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：  
![1147448-20180906013059280-2073338252.png][]

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。  
![1147448-20180906013204996-1354573099.png][]

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>
        
        <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"/>
                
                <property name="suppressAllComments" value="true"/>
            </commentGenerator>
            
            <jdbcConnection driverClass="com.mysql.jdbc.Driver" connectionURL="jdbc:mysql://localhost/test" userId="root" password="123456">
            </jdbcConnection>
            <javaTypeResolver>
                <property name="forceBigDecimals" value="false"/>
            </javaTypeResolver>
            
            <javaModelGenerator targetPackage="com.luis.entity" targetProject="src/main/java">
                <property name="enableSubPackages" value="true"/>
                <property name="trimStrings" value="true"/>
            </javaModelGenerator>
            
            <sqlMapGenerator targetPackage="mapper" targetProject="src/main/resources">
                
                <property name="enableSubPackages" value="false"/>
            </sqlMapGenerator>
            
            <javaClientGenerator type="XMLMAPPER" targetPackage="com.luis.mapper" targetProject="src/main/java">
                
                <property name="enableSubPackages" value="false"/>
            </javaClientGenerator>
            
            <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：  
![1147448-20180906013235916-761967172.png][]

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][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][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][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][]

本文参考了：  
[http://412887952-qq-com.iteye.com/blog/2392672][http_412887952-qq-com.iteye.com_blog_2392672]  
[https://blog.csdn.net/rico\_rico/article/details/79408474][https_blog.csdn.net_rico_rico_article_details_79408474]  
[https://blog.csdn.net/winter\_chen001/article/details/77249029][https_blog.csdn.net_winter_chen001_article_details_77249029]

[1147448-20180906013059280-2073338252.png]: /images/20210923/b473abed5ed14b1db7dbe88a26ac6208.png
[1147448-20180906013204996-1354573099.png]: /images/20210923/937493b474304903ac127bda84581e76.png
[1147448-20180906013235916-761967172.png]: /images/20210923/af13e28a923e4041af180d63dbc8b457.png
[http_412887952-qq-com.iteye.com_blog_2392672]: http://412887952-qq-com.iteye.com/blog/2392672
[http_localhost_8080_test]: http://localhost:8080/test
[http_localhost_8080_list]: http://localhost:8080/list
[github]: https://github.com/liuyi6/JavaWeb/tree/master/springboot-mybatis
[https_blog.csdn.net_rico_rico_article_details_79408474]: https://blog.csdn.net/rico_rico/article/details/79408474
[https_blog.csdn.net_winter_chen001_article_details_77249029]: https://blog.csdn.net/winter_chen001/article/details/77249029