• MyBatis--逆向工程

    MyBatis的逆向工程

    正向工程：先创建Java实体类，由框架负责根据实例类生成数据库表。Hibernate是支持正向工程的。
    逆向工程：先创建数据库表，由框架负责根据数据库表，正向生成如下资源

    • Java实体类
    • Mapper接口
    • Mapper映射文件

    创建逆向工程的步骤

    1. 添加依赖和插件
      pom.xml
    
<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>4.0.0modelVersion>

    <groupId>com.bijing.mybatisgroupId>
    <artifactId>mybatis_dynamicSQLartifactId>
    <version>1.0-SNAPSHOTversion>
    
    <packaging>jarpackaging>

    <properties>
        <maven.compiler.source>11maven.compiler.source>
        <maven.compiler.target>11maven.compiler.target>
    properties>

    <dependencies>
        
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.5.11version>
        dependency>
        
        <dependency>
            <groupId>mysqlgroupId>
            <artifactId>mysql-connector-javaartifactId>
            <version>8.0.30version>
        dependency>
        
        <dependency>
            <groupId>log4jgroupId>
            <artifactId>log4jartifactId>
            <version>1.2.17version>
        dependency>
        
        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <version>4.13.2version>
            <scope>testscope>
        dependency>

    dependencies>

    
    <build>
        
        <plugins>
            
            <plugin>
                <groupId>org.mybatis.generatorgroupId>
                <artifactId>mybatis-generator-maven-pluginartifactId>
                <version>1.4.1version>

                
                <dependencies>
                    
                    <dependency>
                        <groupId>org.mybatis.generatorgroupId>
                        <artifactId>mybatis-generator-coreartifactId>
                        <version>1.4.1version>
                    dependency>

                    
                    <dependency>
                        <groupId>mysqlgroupId>
                        <artifactId>mysql-connector-javaartifactId>
                        <version>8.0.16version>
                    dependency>
                dependencies>
            plugin>
        plugins>
    build>

project>



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    1. 创建MyBatis核心配置文件
      mybatis-config.xml
    
DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    

    
    <properties resource="jdbc.properties">
    properties>

    <settings>
        
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    settings>
    

    <typeAliases>
        <package name="com.bijing.mybatis.pojo"/>
    typeAliases>


    
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            dataSource>
        environment>
    environments>

    
    <mappers>
        <package name="com.bijing.mybatis.mapper"/>
    mappers>
configuration>


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    1. 创建逆向工程的配置文件
      在Resources下， 名字必须是generatorConfig.xml
    
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">
        
        <plugin type="org.mybatis.generator.plugins.SerializablePlugin"/>
        
        <plugin type="org.mybatis.generator.plugins.EqualsHashCodePlugin"/>
        
        <plugin type="org.mybatis.generator.plugins.ToStringPlugin"/>

        <commentGenerator>
            
            <property name="suppressAllComments" value="true"/>
            
            <property name="suppressDate" value="true"/>
            
            <property name="javaFileEncoding" value="utf-8"/>
            
            <property name="javaFormatter" value="org.mybatis.generator.api.dom.DefaultJavaFormatter"/>
            
            <property name="xmlFormatter" value="org.mybatis.generator.api.dom.DefaultXmlFormatter"/>
        commentGenerator>

        
        <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                        connectionURL="jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC"
                        userId="root" password="root1234">
        jdbcConnection>

        
        <javaTypeResolver type="org.mybatis.generator.internal.types.JavaTypeResolverDefaultImpl">
            
            <property name="forceBigDecimals" value="true"/>
        javaTypeResolver>

        
        <javaModelGenerator targetPackage="com.bijing.mybatis.pojo"
                            targetProject="./src/main/java">
            
            <property name="enableSubPackages" value="true"/>
            
            <property name="trimStrings" value="true"/>
        javaModelGenerator>

        
        <sqlMapGenerator targetPackage="com.bijing.mybatis.mapper" targetProject="./src/main/resources">
            <property name="enableSubPackages" value="true"/>
        sqlMapGenerator>

        
        <javaClientGenerator type="XMLMAPPER" targetPackage="com.bijing.mybatis.mapper"
                             targetProject="./src/main/java">
            <property name="enableSubPackages" value="true"/>
        javaClientGenerator>

        
        <table tableName="t_emp" domainObjectName="Emp">
        table>
        <table tableName="t_dept" domainObjectName="Dept"
               enableCountByExample="false"
               enableUpdateByExample="false"
               enableDeleteByExample="false"
               enableSelectByExample="false"
               selectByExampleQueryId="false">table>

    context>
generatorConfiguration>

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    1. 执行MBG插件的generate目标
      在这里插入图片描述

    2. 效果
      自动生成了实例类，映射文件，DAO接口

    QBC查询

    在generatorConfig.xml中如果 targetRuntime=“MyBatis3”，会生成实体类和它的Example

    
    
    <context id="DB2Tables" targetRuntime="MyBatis3">

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    EmpExample.java

    package com.bijing.mybatis.pojo;

import java.util.ArrayList;
import java.util.List;

public class EmpExample {
    protected String orderByClause;

    protected boolean distinct;

    protected List<Criteria> oredCriteria;

    public EmpExample() {
        oredCriteria = new ArrayList<>();
    }

    public void setOrderByClause(String orderByClause) {
        this.orderByClause = orderByClause;
    }

    public String getOrderByClause() {
        return orderByClause;
    }

    public void setDistinct(boolean distinct) {
        this.distinct = distinct;
    }

    public boolean isDistinct() {
        return distinct;
    }

    public List<Criteria> getOredCriteria() {
        return oredCriteria;
    }

    public void or(Criteria criteria) {
        oredCriteria.add(criteria);
    }

    public Criteria or() {
        Criteria criteria = createCriteriaInternal();
        oredCriteria.add(criteria);
        return criteria;
    }

    public Criteria createCriteria() {
        Criteria criteria = createCriteriaInternal();
        if (oredCriteria.size() == 0) {
            oredCriteria.add(criteria);
        }
        return criteria;
    }

    protected Criteria createCriteriaInternal() {
        Criteria criteria = new Criteria();
        return criteria;
    }

    public void clear() {
        oredCriteria.clear();
        orderByClause = null;
        distinct = false;
    }

    protected abstract static class GeneratedCriteria {
        protected List<Criterion> criteria;

        protected GeneratedCriteria() {
            super();
            criteria = new ArrayList<>();
        }

        public boolean isValid() {
            return criteria.size() > 0;
        }

        public List<Criterion> getAllCriteria() {
            return criteria;
        }

        public List<Criterion> getCriteria() {
            return criteria;
        }

        protected void addCriterion(String condition) {
            if (condition == null) {
                throw new RuntimeException("Value for condition cannot be null");
            }
            criteria.add(new Criterion(condition));
        }

        protected void addCriterion(String condition, Object value, String property) {
            if (value == null) {
                throw new RuntimeException("Value for " + property + " cannot be null");
            }
            criteria.add(new Criterion(condition, value));
        }

        protected void addCriterion(String condition, Object value1, Object value2, String property) {
            if (value1 == null || value2 == null) {
                throw new RuntimeException("Between values for " + property + " cannot be null");
            }
            criteria.add(new Criterion(condition, value1, value2));
        }

        public Criteria andEmpIdIsNull() {
            addCriterion("emp_id is null");
            return (Criteria) this;
        }

        public Criteria andEmpIdIsNotNull() {
            addCriterion("emp_id is not null");
            return (Criteria) this;
        }

        public Criteria andEmpIdEqualTo(Integer value) {
            addCriterion("emp_id =", value, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdNotEqualTo(Integer value) {
            addCriterion("emp_id <>", value, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdGreaterThan(Integer value) {
            addCriterion("emp_id >", value, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdGreaterThanOrEqualTo(Integer value) {
            addCriterion("emp_id >=", value, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdLessThan(Integer value) {
            addCriterion("emp_id <", value, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdLessThanOrEqualTo(Integer value) {
            addCriterion("emp_id <=", value, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdIn(List<Integer> values) {
            addCriterion("emp_id in", values, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdNotIn(List<Integer> values) {
            addCriterion("emp_id not in", values, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdBetween(Integer value1, Integer value2) {
            addCriterion("emp_id between", value1, value2, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpIdNotBetween(Integer value1, Integer value2) {
            addCriterion("emp_id not between", value1, value2, "empId");
            return (Criteria) this;
        }

        public Criteria andEmpNameIsNull() {
            addCriterion("emp_name is null");
            return (Criteria) this;
        }

        public Criteria andEmpNameIsNotNull() {
            addCriterion("emp_name is not null");
            return (Criteria) this;
        }

        public Criteria andEmpNameEqualTo(String value) {
            addCriterion("emp_name =", value, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameNotEqualTo(String value) {
            addCriterion("emp_name <>", value, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameGreaterThan(String value) {
            addCriterion("emp_name >", value, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameGreaterThanOrEqualTo(String value) {
            addCriterion("emp_name >=", value, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameLessThan(String value) {
            addCriterion("emp_name <", value, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameLessThanOrEqualTo(String value) {
            addCriterion("emp_name <=", value, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameLike(String value) {
            addCriterion("emp_name like", value, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameNotLike(String value) {
            addCriterion("emp_name not like", value, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameIn(List<String> values) {
            addCriterion("emp_name in", values, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameNotIn(List<String> values) {
            addCriterion("emp_name not in", values, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameBetween(String value1, String value2) {
            addCriterion("emp_name between", value1, value2, "empName");
            return (Criteria) this;
        }

        public Criteria andEmpNameNotBetween(String value1, String value2) {
            addCriterion("emp_name not between", value1, value2, "empName");
            return (Criteria) this;
        }

        public Criteria andAgeIsNull() {
            addCriterion("age is null");
            return (Criteria) this;
        }

        public Criteria andAgeIsNotNull() {
            addCriterion("age is not null");
            return (Criteria) this;
        }

        public Criteria andAgeEqualTo(Integer value) {
            addCriterion("age =", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeNotEqualTo(Integer value) {
            addCriterion("age <>", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeGreaterThan(Integer value) {
            addCriterion("age >", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeGreaterThanOrEqualTo(Integer value) {
            addCriterion("age >=", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeLessThan(Integer value) {
            addCriterion("age <", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeLessThanOrEqualTo(Integer value) {
            addCriterion("age <=", value, "age");
            return (Criteria) this;
        }

        public Criteria andAgeIn(List<Integer> values) {
            addCriterion("age in", values, "age");
            return (Criteria) this;
        }

        public Criteria andAgeNotIn(List<Integer> values) {
            addCriterion("age not in", values, "age");
            return (Criteria) this;
        }

        public Criteria andAgeBetween(Integer value1, Integer value2) {
            addCriterion("age between", value1, value2, "age");
            return (Criteria) this;
        }

        public Criteria andAgeNotBetween(Integer value1, Integer value2) {
            addCriterion("age not between", value1, value2, "age");
            return (Criteria) this;
        }

        public Criteria andGenderIsNull() {
            addCriterion("gender is null");
            return (Criteria) this;
        }

        public Criteria andGenderIsNotNull() {
            addCriterion("gender is not null");
            return (Criteria) this;
        }

        public Criteria andGenderEqualTo(String value) {
            addCriterion("gender =", value, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderNotEqualTo(String value) {
            addCriterion("gender <>", value, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderGreaterThan(String value) {
            addCriterion("gender >", value, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderGreaterThanOrEqualTo(String value) {
            addCriterion("gender >=", value, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderLessThan(String value) {
            addCriterion("gender <", value, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderLessThanOrEqualTo(String value) {
            addCriterion("gender <=", value, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderLike(String value) {
            addCriterion("gender like", value, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderNotLike(String value) {
            addCriterion("gender not like", value, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderIn(List<String> values) {
            addCriterion("gender in", values, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderNotIn(List<String> values) {
            addCriterion("gender not in", values, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderBetween(String value1, String value2) {
            addCriterion("gender between", value1, value2, "gender");
            return (Criteria) this;
        }

        public Criteria andGenderNotBetween(String value1, String value2) {
            addCriterion("gender not between", value1, value2, "gender");
            return (Criteria) this;
        }

        public Criteria andDeptIdIsNull() {
            addCriterion("dept_id is null");
            return (Criteria) this;
        }

        public Criteria andDeptIdIsNotNull() {
            addCriterion("dept_id is not null");
            return (Criteria) this;
        }

        public Criteria andDeptIdEqualTo(Integer value) {
            addCriterion("dept_id =", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdNotEqualTo(Integer value) {
            addCriterion("dept_id <>", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdGreaterThan(Integer value) {
            addCriterion("dept_id >", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdGreaterThanOrEqualTo(Integer value) {
            addCriterion("dept_id >=", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdLessThan(Integer value) {
            addCriterion("dept_id <", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdLessThanOrEqualTo(Integer value) {
            addCriterion("dept_id <=", value, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdIn(List<Integer> values) {
            addCriterion("dept_id in", values, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdNotIn(List<Integer> values) {
            addCriterion("dept_id not in", values, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdBetween(Integer value1, Integer value2) {
            addCriterion("dept_id between", value1, value2, "deptId");
            return (Criteria) this;
        }

        public Criteria andDeptIdNotBetween(Integer value1, Integer value2) {
            addCriterion("dept_id not between", value1, value2, "deptId");
            return (Criteria) this;
        }
    }

    public static class Criteria extends GeneratedCriteria {
        protected Criteria() {
            super();
        }
    }

    public static class Criterion {
        private String condition;

        private Object value;

        private Object secondValue;

        private boolean noValue;

        private boolean singleValue;

        private boolean betweenValue;

        private boolean listValue;

        private String typeHandler;

        public String getCondition() {
            return condition;
        }

        public Object getValue() {
            return value;
        }

        public Object getSecondValue() {
            return secondValue;
        }

        public boolean isNoValue() {
            return noValue;
        }

        public boolean isSingleValue() {
            return singleValue;
        }

        public boolean isBetweenValue() {
            return betweenValue;
        }

        public boolean isListValue() {
            return listValue;
        }

        public String getTypeHandler() {
            return typeHandler;
        }

        protected Criterion(String condition) {
            super();
            this.condition = condition;
            this.typeHandler = null;
            this.noValue = true;
        }

        protected Criterion(String condition, Object value, String typeHandler) {
            super();
            this.condition = condition;
            this.value = value;
            this.typeHandler = typeHandler;
            if (value instanceof List<?>) {
                this.listValue = true;
            } else {
                this.singleValue = true;
            }
        }

        protected Criterion(String condition, Object value) {
            this(condition, value, null);
        }

        protected Criterion(String condition, Object value, Object secondValue, String typeHandler) {
            super();
            this.condition = condition;
            this.value = value;
            this.secondValue = secondValue;
            this.typeHandler = typeHandler;
            this.betweenValue = true;
        }

        protected Criterion(String condition, Object value, Object secondValue) {
            this(condition, value, secondValue, null);
        }
    }
}

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    EmpMapper.java
    在generatorConfig.xml中如果 targetRuntime=“MyBatis3”，会生成实体类和它的Example
    MyBatis3Simple:生成基本的CRUD
    MyBatis3:生成带条件的CRUD
    有了EmpExample就可以对单表进行条件查询

    package com.bijing.mybatis.mapper;

import com.bijing.mybatis.pojo.Emp;
import com.bijing.mybatis.pojo.EmpExample;
import org.apache.ibatis.annotations.Param;

import java.util.List;

public interface EmpMapper {
    long countByExample(EmpExample example);

    //按条件删除
    int deleteByExample(EmpExample example);

    //按主键删除
    int deleteByPrimaryKey(Integer empId);

    int insert(Emp row);

    //选择性添加
    int insertSelective(Emp row);

    List<Emp> selectByExample(EmpExample example);

    Emp selectByPrimaryKey(Integer empId);

    //选择性修改,某个属性为null的时候不会修改这个字段
    int updateByExampleSelective(@Param("row") Emp row, @Param("example") EmpExample example);

    //普通修改,某个属性为null的时候会将字段修改为null
    int updateByExample(@Param("row") Emp row, @Param("example") EmpExample example);

    int updateByPrimaryKeySelective(Emp row);

    int updateByPrimaryKey(Emp row);
}

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  • 原文地址：https://blog.csdn.net/weixin_43903745/article/details/127339538