spring boot學習（04）：mybatis自動生成代碼和分頁功能

前言

前面介紹了spring boot整合mybatis，但是發現發現需要手動的寫大量的xlm文件和實體類，十分麻煩。我們知道mybatis提供了逆向工程（generator ）自動生成代碼，此篇文章介紹此內容。
編輯器：idea
數據庫：mysql

1.第一步：創建一個spring boot項目

此處不多介紹，記得添加依賴，pom.xml樣板

<?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 自動生成插件-->
        <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>
</project>

2.編寫generatorConfig.xml文件（文件位置在pom.xml中屬性）

<?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>
    <!-- 數據庫驅動:選擇你的本地硬盤上面的數據庫驅動包-->
    <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"/>
            <!-- 是否去除自動生成的註釋 true：是 ： false:否 -->
            <property name="suppressAllComments" value="true"/>
        </commentGenerator>
        <!--數據庫鏈接URL，用戶名、密碼 -->
        <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是數據庫中的表名或視圖名 domainObjectName是實體類名-->
        <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中生成代碼

然後Apply–>ok， 運行，代碼自動生成。

查看生成的代碼：

分頁功能

1.添加依賴

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

2.配置我們的PageHelper

可以直接在application中直接設置PageHelper插件

//配置mybatis的分頁插件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數據庫的方言
    pageHelper.setProperties(properties);
    return pageHelper;
}

3.使用插件的分頁功能

import java.util.List;

public class PageBean<T> {
    // 當前頁
    private Integer currentPage = 1;
    // 每頁顯示的總條數
    private Integer pageSize = 10;
    // 總條數
    private Integer totalNum;
    // 是否有下一頁
    private Integer isMore;
    // 總頁數
    private Integer totalPage;
    // 開始索引
    private Integer startIndex;
    // 分頁結果
    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) {
        //設置分頁信息，分別是當前頁數和每頁顯示的總記錄數【記住：必須在mapper接口中的方法執行之前設置該分頁信息】
        PageHelper.startPage(currentPage, pageSize);
        List<UserModel> allItems = userDao.getAllUser(tableName);    
        int countNums = allItems.size();            //總記錄數
        PageBean<UserModel> pageData = new PageBean<>(currentPage, pageSize, countNums);
        pageData.setItems(allItems);
        return pageData.getItems();

可能遇到的問題

現在我們在使用數據庫的時候，都會去配置Druid數據庫連接池，假如你在配置druid連接
池的時候，重新設置了SqlSessionFactory，那麼第二步的配置PageHelper就不能單獨配置一個bean了，而是需要配置在SqlSessionFactory裏面了，如下，那麼就可以順利解決查詢不分頁的問題。

@Bean
    public SqlSessionFactory sqlSessionFactory() throws Exception {
        SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
        sqlSessionFactoryBean.setDataSource(druidDataSource());
        //mybatis分頁
        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目錄
        VFS.addImplClass(SpringBootVFS.class);
        PathMatchingResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        sqlSessionFactoryBean.setMapperLocations(resolver.getResources("classpath:mapper/*.xml"));
        logger.info("dao層掃描包爲:mapper/*.xml");
        return sqlSessionFactoryBean.getObject();