spring boot学习（04）：mybatis自动生成代码和分页功能

前言

前面介绍了spring boot整合mybatis，但是发现发现需要手动的写大量的xlm文件和实体类，十分麻烦。我们知道mybatis提供了逆向工程（generator ）自动生成代码，此篇文章介绍此内容。
编辑器：idea
数据库：mysql

1.第一步：创建一个spring boot项目

此处不多介绍，记得添加依赖，pom.xml样板

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.neo</groupId>
    <artifactId>demo-generator</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>demo-generator</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.8.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>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <!--mybatis 自动生成插件-->
        <dependency>
            <groupId>org.mybatis.generator</groupId>
            <artifactId>mybatis-generator-core</artifactId>
            <version>1.3.5</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>
</project>

2.编写generatorConfig.xml文件（文件位置在pom.xml中属性）

<?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="C:\Users\mia\.m2\repository\mysql\mysql-connector-java\5.1.44\mysql-connector-java-5.1.44.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://172.16.100.92/test1" userId="root" password="root">
        </jdbcConnection>
        <javaTypeResolver>
            <property name="forceBigDecimals" value="false"/>
        </javaTypeResolver>
        <!-- 生成模型的包名和位置-->
        <javaModelGenerator targetPackage="com.neo.demo.model" 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="resources.mapping" targetProject="src/main">
            <property name="enableSubPackages" value="true"/>
        </sqlMapGenerator>
        <!-- 生成DAO的包名和位置-->
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.neo.demo.mapper" targetProject="src/main/java">
            <property name="enableSubPackages" value="true"/>
        </javaClientGenerator>
        <!-- 要生成的表 tableName是数据库中的表名或视图名 domainObjectName是实体类名-->
        <table tableName="dept" domainObjectName="dept" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"></table>
        <table tableName="emp" domainObjectName="emp" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"></table>
        <table tableName="salgrade" domainObjectName="salgrade" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"></table>
    </context>
</generatorConfiguration>

3.idea中生成代码

然后Apply–>ok， 运行，代码自动生成。

查看生成的代码：

分页功能

1.添加依赖

<dependency>
   <groupId>com.github.pagehelper</groupId>
   <artifactId>pagehelper</artifactId>
   <version>4.1.6</version>
</dependency>

2.配置我们的PageHelper

可以直接在application中直接设置PageHelper插件

//配置mybatis的分页插件pageHelper
@Bean
public PageHelper pageHelper(){
    PageHelper pageHelper = new PageHelper();
    Properties properties = new Properties();
    properties.setProperty("offsetAsPageNum","true");
    properties.setProperty("rowBoundsWithCount","true");
    properties.setProperty("reasonable","true");
    properties.setProperty("dialect","mysql");    //配置mysql数据库的方言
    pageHelper.setProperties(properties);
    return pageHelper;
}

3.使用插件的分页功能

import java.util.List;

public class PageBean<T> {
    // 当前页
    private Integer currentPage = 1;
    // 每页显示的总条数
    private Integer pageSize = 10;
    // 总条数
    private Integer totalNum;
    // 是否有下一页
    private Integer isMore;
    // 总页数
    private Integer totalPage;
    // 开始索引
    private Integer startIndex;
    // 分页结果
    private List<T> items;

    public PageBean() {
        super();
    } 
    public PageBean(Integer currentPage, Integer pageSize, Integer totalNum) {
        super();
        this.currentPage = currentPage;
        this.pageSize = pageSize;
        this.totalNum = totalNum;
        this.totalPage = (this.totalNum+this.pageSize-1)/this.pageSize;
        this.startIndex = (this.currentPage-1)*this.pageSize;
        this.isMore = this.currentPage >= this.totalPage?0:1;
    } 
    public Integer getCurrentPage() {
        return currentPage;
    } 
    public void setCurrentPage(Integer currentPage) {
        this.currentPage = currentPage;
    } 
    public Integer getPageSize() {
        return pageSize;
    } 
    public void setPageSize(Integer pageSize) {
        this.pageSize = pageSize;
    } 
    public Integer getTotalNum() {
        return totalNum;
    }
    public void setTotalNum(Integer totalNum) {
        this.totalNum = totalNum;
    } 
    public Integer getIsMore() {
        return isMore;
    }
    public void setIsMore(Integer isMore) {
        this.isMore = isMore;
    }
    public Integer getTotalPage() {
        return totalPage;
    }
    public void setTotalPage(Integer totalPage) {
        this.totalPage = totalPage;
    } 
    public Integer getStartIndex() {
        return startIndex;
    } 
    public void setStartIndex(Integer startIndex) {
        this.startIndex = startIndex;
    }
     public List<T> getItems() {
        return items;
    }
    public void setItems(List<T> items) {
        this.items = items;
    }
}

4.直接使用

@Override
    public List<UserModel> findUserModelByPage(int currentPage, int pageSize,String tableName) {
        //设置分页信息，分别是当前页数和每页显示的总记录数【记住：必须在mapper接口中的方法执行之前设置该分页信息】
        PageHelper.startPage(currentPage, pageSize);
        List<UserModel> allItems = userDao.getAllUser(tableName);    
        int countNums = allItems.size();            //总记录数
        PageBean<UserModel> pageData = new PageBean<>(currentPage, pageSize, countNums);
        pageData.setItems(allItems);
        return pageData.getItems();

可能遇到的问题

现在我们在使用数据库的时候，都会去配置Druid数据库连接池，假如你在配置druid连接
池的时候，重新设置了SqlSessionFactory，那么第二步的配置PageHelper就不能单独配置一个bean了，而是需要配置在SqlSessionFactory里面了，如下，那么就可以顺利解决查询不分页的问题。

@Bean
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(druidDataSource());
        //mybatis分页
        PageHelper pageHelper = new PageHelper();
        Properties props = new Properties();
        props.setProperty("dialect", "mysql");
        props.setProperty("reasonable", "true");
        props.setProperty("supportMethodsArguments", "true");
        props.setProperty("returnPageInfo", "check");
        props.setProperty("params", "count=countSql");
        pageHelper.setProperties(props);
        //添加插件
       sqlSessionFactoryBean.setPlugins(new Interceptor[]{pageHelper});
        //添加XML目录
        VFS.addImplClass(SpringBootVFS.class);
        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        sqlSessionFactoryBean.setMapperLocations(resolver.getResources("classpath:mapper/*.xml"));
        logger.info("dao层扫描包为:mapper/*.xml");
        return sqlSessionFactoryBean.getObject();