mybatis逆向工程与分页在springboot中的应用

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

本文参考了：
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