最近在項目中應用到springboot與mybatis，在進行整合過程中遇到一些坑，在此將其整理出來，便於以後查閱與複習。項目運行環境為：eclispe+jdk1.8+maven 搭建Spring Boot環境 === 首先建立maven project,在生成的pom文件中加入依賴，代碼如下： ...

最近在項目中應用到springboot與mybatis，在進行整合過程中遇到一些坑，在此將其整理出來，便於以後查閱與複習。
項目運行環境為：eclispe+jdk1.8+maven

搭建Spring Boot環境

首先建立maven project,在生成的pom文件中加入依賴，代碼如下：

<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>
    
    <!--分頁插件-->
    <dependency>
          <groupId>com.github.pagehelper</groupId>
          <artifactId>pagehelper-spring-boot-starter</artifactId>
          <version>1.2.1</version>
    </dependency>
    
    <!-- alibaba的druid資料庫連接池 -->
    <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 自動生成代碼插件 -->
        <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>

配置好依賴後進行maven install,此時註意的坑：
坑一：啟動maven install報錯：

[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

報錯原因是沒有啟動類
解決方法:編寫啟動類Main.java正常運行！

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

坑二：啟動maven install報錯：

[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

報錯原因：項目的java環境與電腦環境不符合，例如我的新建項目運行環境為J2SE-1.5,報錯是在我將其改為jre1.8之後
解決方案：
右鍵項目——build path——Configure build path——Libraries——雙擊Jre System Libraries如下圖所示：

選擇Alternate JRE 如2處的下拉框只有jre，點擊3處的Install JREs，依次經過add——Standard VM——next——Directory,選擇本機的jdk位置點擊finish
在install JREs位置將預設勾選更改jdk,如下圖所示，並保存。

再次maven install項目正常。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，內容如下所示：

server:
  port: 8080

spring:
    datasource:
        name: test
        url: jdbc:mysql://localhost:3306/test
        username: root
        password: 123456
        driver-class-name: com.mysql.jdbc.Driver

## 該配置節點為獨立的節點
mybatis:
  mapper-locations: classpath:mapper/*.xml
  
#pagehelper分頁插件
pagehelper:
    helperDialect: mysql
    reasonable: true
    supportMethodsArguments: true
    params: count=countSql

至此springboot環境搭建完畢！

逆向工程應用

首先應該註意到在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文件夾，並建立generatorConfig.xml文件，代碼如下：

<?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>
    <!-- 資料庫驅動:選擇你的本地硬碟上面的資料庫驅動包-->
    <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"/>
            <!-- 是否去除自動生成的註釋 true：是 ： false:否 -->
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <!--資料庫鏈接URL，用戶名、密碼 -->
        <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類的位置-->
        <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 是否讓schema作為包的尾碼-->
            <property name="enableSubPackages" value="false"/>
        </sqlMapGenerator>
        <!-- 生成mapper介面的位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.luis.mapper" targetProject="src/main/java">
            <!-- enableSubPackages 是否讓schema作為包的尾碼-->
            <property name="enableSubPackages" value="false"/>
        </javaClientGenerator>
        <!-- 指定資料庫表 -->
        <table schema="" tableName="user"></table>
    </context>
</generatorConfiguration>

根據個人環境將配置文件中的配置進行更改，如資料庫密碼，包名，對應資料庫表
所用的資料庫表如下：

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');

配置完成後，右鍵項目，選擇run as——Maven build——在下麵兩處分別填入：
Goals: mybatis-generator:generate -e
Profiles: generatorConfig.xml
如下圖所示：

出現如下所示，代碼生成成功，刷新項目即可。

[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] ------------------------------------------------------------------------

需要註意的是：逆向工程生成的代碼不會覆蓋，因而不能重覆多次生成。
此處也有個小坑，逆向工程的代碼生成後，啟動項目會報如下錯誤：

***************************
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.

解決方案：
1、給生成的mapper介面文件前加註解：@Mapper 即可解決。但需要給每一個mapper文件前加，繁瑣，因而有第二種類解決辦法
2、在啟動類前加@MapperScan({"com.luis.mapper"})，其中com.luis.mapper為mapper文件的所在位置。
參考自：http://412887952-qq-com.iteye.com/blog/2392672

分頁應用

逆向工程已經生成了entity類，及dao層的mapper介面與*mapper.xml文件，因而/只用編寫service層與web層。
首先在UserService中編寫介面，代碼如下：

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

在UserServiceImpl文件進行實現，代碼如下所示：

@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 開始頁數
     * pageSize 每頁顯示的數據條數
     */
    @Override
    public List<User> findAllUser(int pageNum, int pageSize) {
        //將參數傳給方法實現分頁
        PageHelper.startPage(pageNum, pageSize);
        UserExample example = new UserExample();
        List<User> list = userMapper.selectByExample(example);
        return list;
    }
}

最後在controller層對查詢結果進行接收，UserController代碼如下：

@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);
        //獲取分頁信息
        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;
    }
}

測試

此前在項目編寫過程中已經對可能出現的錯誤進行了總結，最後，對項目的功能進行測試，通過加@RestController註解將數據傳輸到瀏覽器中。
測試mybatis與springboot，瀏覽器輸入http://localhost:8080/test，瀏覽器輸出：

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

分頁測試，瀏覽器輸入http://localhost:8080/list，瀏覽器輸出：

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

eclipse輸出：

total:4
pages:2
pageSize:2

項目搭建完畢，具體代碼參見github

本文參考了：
http://412887952-qq-com.iteye.com/blog/2392672
https://blog.csdn.net/rico_rico/article/details/79408474
https://blog.csdn.net/winter_chen001/article/details/77249029

mybatis逆向工程與分頁在springboot中的應用

搭建Spring Boot環境

逆向工程應用

分頁應用

測試