【Spring Boot 24】MyBatis逆向工程（Example + Criteria简介）

￡神魔★判官ぃ 2021-09-03 03:52 715阅读 0赞

mybatis需要编写sql语句，mybatis官方提供提箱工程，可以针对单表自动生成mybatis执行所需要的代码（诸如bean、dao、mapper），提高工作效率，尤其是在需要大量表进行单表查询的时候，效率极高，快速搭建项目框架的福音。

## 一、Example + Criteria简介 ##

Example类指定如何构建一个动态的where子句，表中的每个non-BLOB列可以被包括在where子句中。

Example类可以用来生成一个几乎无限的where子句。

Example类包含一个内部静态类 Criteria 包含一个用 anded 组合在where子句中的条件列表。Example类包含一个 List 属性,所有内部类Criteria中的子句会用 ored组合在一起，使用不同属性的 Criteria 类允许您生成无限类型的where子句.。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2d1b3J1aV9qYXZh_size_16_color_FFFFFF_t_70][]

创建 Criteria 对象 可以使用Example类中的 createCriteria() 或者 or()， 如果 Criteria 对象是用 createCriteria() 创建的，它会自动为 List 属性添加一个 Criteria 对象 - 这使得它更容易写一个简单的where子句， 如果您不需要 or 或者其他几个子句组合的话，用 or(Criteria criteria) 方法创建 Criteria 对象，方法里的 criteria 对象会被添加进 Criteria 对象的列表中。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2d1b3J1aV9qYXZh_size_16_color_FFFFFF_t_70 1][]

## 二、创建SpringBoot工程，添加POM ##

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    	<modelVersion>4.0.0</modelVersion>
    	<parent>
    		<groupId>org.springframework.boot</groupId>
    		<artifactId>spring-boot-starter-parent</artifactId>
    		<version>2.4.0</version>
    		<relativePath/> 
    	</parent>
    	<groupId>com.guor</groupId>
    	<artifactId>MyBatisGenerator</artifactId>
    	<version>0.0.1-SNAPSHOT</version>
    	<name>MyBatisGenerator</name>
    	<description>Demo project for Spring Boot</description>
    
    	<properties>
    		<java.version>1.8</java.version>
    	</properties>
    
    	<dependencies>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-web</artifactId>
    		</dependency>
    		<dependency>
    			<groupId>org.mybatis.spring.boot</groupId>
    			<artifactId>mybatis-spring-boot-starter</artifactId>
    			<version>2.1.4</version>
    		</dependency>
    	    <dependency>
    			<groupId>org.mybatis.generator</groupId>
    			<artifactId>mybatis-generator-maven-plugin</artifactId>
    			<version>1.3.2</version>
    		</dependency>
    		<dependency>
    			<groupId>com.oracle.database.jdbc</groupId>
    			<artifactId>ojdbc8</artifactId>
    			<scope>runtime</scope>
    		</dependency>
    		<dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid</artifactId>
                <version>1.0.20</version>
     		</dependency>
    		<dependency>
    			<groupId>cn.easyproject</groupId>
    			<artifactId>orai18n</artifactId>
    			<version>12.1.0.2.0</version>
    		</dependency>
    		<dependency>
    			<groupId>org.springframework.boot</groupId>
    			<artifactId>spring-boot-starter-test</artifactId>
    			<scope>test</scope>
    		</dependency>
    	</dependencies>
    
    	<build>
    		<plugins>
    			<plugin>
    				<groupId>org.springframework.boot</groupId>
    				<artifactId>spring-boot-maven-plugin</artifactId>
    			</plugin>
    		</plugins>
    	</build>
    
    </project>

## 三、配置文件 ##

### 1、application.properties ###

spring.datasource.driverClassName=oracle.jdbc.driver.OracleDriver
    spring.datasource.url=jdbc:oracle:thin:@127.0.0.1:1521:orcl
    spring.datasource.username=mine
    spring.datasource.password=mine

### 2、逆向工程模板，此博客的核心 ###

<?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>
        <context id="DB2Tables" targetRuntime="Mybatis3">
            
         
            
            <commentGenerator>
                <property name="suppressDate" value="true" />
                <property name="suppressAllComments" value="true" />
            </commentGenerator>
            
            <jdbcConnection driverClass="oracle.jdbc.driver.OracleDriver" connectionURL="jdbc:oracle:thin:@127.0.0.1:1521:orcl"
            userId="mine" password="mine"/>
            
            <javaTypeResolver>
                
                <property name="forceBigDecimals" value="false"/>
            </javaTypeResolver>
            
            <javaModelGenerator targetPackage="com.guor.entity" targetProject="src/main/java">
                
                <property name="enableSubPackages" value="true"/>
                
                <property name="trimString" value="true" />
            </javaModelGenerator>
            
            <sqlMapGenerator targetPackage="com.guor.mapper" targetProject="src/main/java">
                <property name="enableSubPackages" value="true"/>
            </sqlMapGenerator>
            
            <javaClientGenerator type="XMLMAPPER" targetPackage="com.guor.mapper" targetProject="src/main/java">
                <property name="enableSubPackages" value="true"/>
            </javaClientGenerator>
            <table tableName="student" />
            
            
        </context>
    </generatorConfiguration>

## 四、加载generator.xml模板 ##

package com.guor;
    
    import java.io.File;
    import java.util.ArrayList;
    import java.util.List;
    
    import org.mybatis.generator.api.MyBatisGenerator;
    import org.mybatis.generator.config.Configuration;
    import org.mybatis.generator.config.xml.ConfigurationParser;
    import org.mybatis.generator.internal.DefaultShellCallback;
    
    public class MybatisGenerator {
    	public static void main(String[] args) throws Exception {
    		File file = new File("src/generator.xml");
            System.out.println("开始逆向！！！");
            List<String> warnings = new ArrayList<String>();
            ConfigurationParser cp = new ConfigurationParser(warnings);
            Configuration config = cp.parseConfiguration(file);
            DefaultShellCallback callback = new DefaultShellCallback(true);
            MyBatisGenerator myBatisGenerator = new MyBatisGenerator(config, callback, warnings);
            myBatisGenerator.generate(null);
            System.out.println("生成代码成功");
        }
    }

执行main方法，生成代码。

![20201129140113461.png][]

## 五、创建controller，进行测试 ##

### 1、controller ###

package com.guor.controller;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    
    import com.guor.entity.Student;
    import com.guor.entity.StudentExample;
    import com.guor.entity.StudentExample.Criteria;
    import com.guor.mapper.StudentMapper;
    
    @Controller
    @RequestMapping("/generator")
    public class StudentController {
    	@Autowired
    	private StudentMapper mapper;
    	
    	@RequestMapping(path = "/getStudents", method=RequestMethod.GET)
        public Student getStudents(){
    		Student student = mapper.selectByPrimaryKey((short)1);
    		System.out.println(student);
    		return student;
    	}
    	
    	@RequestMapping(path = "/getStudentsByExample", method=RequestMethod.GET)
        public void getStudentsByExample(){
    		StudentExample example = new StudentExample();
    		Criteria criteria = example.createCriteria();
    		criteria.andAgeBetween((short)18, (short)28);
    		criteria.andNameLike("%k%");
    		
    		Criteria criteria2 = example.createCriteria();
    		criteria2.andNameLike("%j%");
    		
    		example.or(criteria2);//相当于where (age>18 and age<28 and name like '%k%') or name like '%j%';
    		
    		List<Student> list = mapper.selectByExample(example);
    		System.out.println(list);
    	}
    }

### 2、简单的查询  ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2d1b3J1aV9qYXZh_size_16_color_FFFFFF_t_70 2][]

### 3、带or的查询 ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2d1b3J1aV9qYXZh_size_16_color_FFFFFF_t_70 3][]

## 六、逆向工程在实际开发中用的多吗？ ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2d1b3J1aV9qYXZh_size_16_color_FFFFFF_t_70 4][]

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[Java_SSH_SSM_Springboot]: https://blog.csdn.net/guorui_java/article/details/104018528
[springBoot]: https://blog.csdn.net/guorui_java/article/details/104137262