一、介绍
我记得最早刚步入互联网行业的时候，当时按照 MVC 的思想和模型，每次开发新功能，会依次编写 dao、service、controller相关服务类，包括对应的 dto、entity、vo 等等实体类，如果有多张单表，也会重复的编写相似的代码，现在回想起来，感觉当时自己好像处于石器时代!
实际上，当仔细的总结一下，对于任何一张单表的操作，基本都是围绕增(Create )、删(Delete )、改(Update )、查(Retrieve )四个方向进行数据操作，简称 CRUD!
他们除了表名和存储空间不一样，基本的 CRUD 思路基本都是一样的。
为了解决这些重复劳动的痛点，业界逐渐开源了一批代码生成器，目的也很简单，就是为了减少手工操作的繁琐，集中精力在业务开发上，提升开发效率。
而今天，我们所要介绍的也是代码生成器，很多初学者可能觉得代码生成器很高深。代码生成器其实是一个很简单的东西，一点都不高深。
当你看完本文的时候，你会完全掌握代码生成器的逻辑，甚至可以根据自己的项目情况，进行深度定制。
二、实现思路
下面我们就以SpringBoot项目为例，数据持久化操作采用Mybatis，数据库采用Mysql，编写一个自动生成增、删、改、查等基础功能的代码生成器，内容包括controller、service、dao、entity、dto、vo等信息。
实现思路如下：
第一步：获取表字段名称、类型、表注释等信息
第二步：基于 freemarker 模板引擎，编写相应的模板
第三步：根据对应的模板，生成相应的 java 代码
2.1、获取表结构
首先我们创建一张test_db表，脚本如下：
CREATE TABLE test_db (
id bigint(20) unsigned NOT NULL COMMENT '主键ID',
name varchar(50) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '' COMMENT '名称',
is_delete tinyint(4) NOT NULL DEFAULT '0' COMMENT '是否删除 1：已删除；0：未删除',
create_time datetime NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
update_time datetime NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '更新时间',
PRIMARY KEY (id),
KEY idx_create_time (create_time) USING BTREE
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='测试表';
表创建完成之后，基于test_db表，我们查询对应的表结果字段名称、类型、备注信息，这些关键信息将用于后续进行代码生成器所使用!
# 获取对应表结构
SELECT column_name, data_type, column_comment FROM information_schema.columns WHERE table_schema = 'yjgj_base' AND table_name = 'test_db
同时，获取对应表注释，用于生成备注信息!
# 获取对应表注释
SELECT TABLE_COMMENT FROM INFORMATION_SCHEMA.TABLES WHERE table_schema = 'yjgj_base' AND table_name = 'test_db'
2.2、编写模板
编写mapper.ftl模板，涵盖新增、修改、删除、查询等信息
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="${daoPackageName}.${daoName}">
<!--BaseResultMap-->
<resultMap id="BaseResultMap" type="${entityPackageName}.${entityName}">
<#list columns as pro>
<#if pro.proName == primaryId>
<id column="${primaryId}" property="${primaryId}" jdbcType="${pro.fieldType}"/>
<#else>
<result column="${pro.fieldName}" property="${pro.proName}" jdbcType="${pro.fieldType}"/>
</#if>
</#list>
</resultMap>
<!--Base_Column_List-->
<sql id="Base_Column_List">
<#list columns as pro>
<#if pro_index == 0>${pro.fieldName}<#else>,${pro.fieldName}</#if>
</#list>
</sql>
<!--批量插入-->
<insert id="insertList" parameterType="java.util.List">
insert into ${tableName} (
<#list columns as pro>
<#if pro_index == 0>${pro.fieldName},<#elseif pro_index == 1>${pro.fieldName}<#else>,${pro.fieldName}</#if>
</#list>
)
values
<foreach collection ="list" item="obj" separator =",">
<trim prefix=" (" suffix=")" suffixOverrides=",">
<#list columns as pro>
${r"#{obj." + pro.proName + r"}"},
</#list>
</trim>
</foreach >
</insert>
<!--按需新增-->
<insert id="insertPrimaryKeySelective" parameterType="${entityPackageName}.${entityName}">
insert into ${tableName}
<trim prefix="(" suffix=")" suffixOverrides=",">
<#list columns as pro>
<if test="${pro.proName} != null">
${pro.fieldName},
</if>
</#list>
</trim>
<trim prefix="values (" suffix=")" suffixOverrides=",">
<#list columns as pro>
<if test="${pro.proName} != null">
${r"#{" + pro.proName + r",jdbcType=" + pro.fieldType +r"}"},
</if>
</#list>
</trim>
</insert>
<!-- 按需修改-->
<update id="updatePrimaryKeySelective" parameterType="${entityPackageName}.${entityName}">
update ${tableName}
<set>
<#list columns as pro>
<#if pro.fieldName != primaryId && pro.fieldName != primaryId>
<if test="${pro.proName} != null">
${pro.fieldName} = ${r"#{" + pro.proName + r",jdbcType=" + pro.fieldType +r"}"},
</if>
</#if>
</#list>
</set>
where ${primaryId} = ${r"#{" + "${primaryId}" + r",jdbcType=BIGINT}"}
</update>
<!-- 按需批量修改-->
<update id="updateBatchByIds" parameterType="java.util.List">
update ${tableName}
<trim prefix="set" suffixOverrides=",">
<#list columns as pro>
<#if pro.fieldName != primaryId && pro.fieldName != primaryId>
<trim prefix="${pro.fieldName}=case" suffix="end,">
<foreach collection="list" item="obj" index="index">
<if test="obj.${pro.proName} != null">
when id = ${r"#{" + "obj.id" + r"}"}
then ${r"#{obj." + pro.proName + r",jdbcType=" + pro.fieldType +r"}"}
</if>
</foreach>
</trim>
</#if>
</#list>
</trim>
where
<foreach collection="list" separator="or" item="obj" index="index" >
id = ${r"#{" + "obj.id" + r"}"}
</foreach>
</update>
<!-- 删除-->
<delete id="deleteByPrimaryKey" parameterType="java.lang.Long">
delete from ${tableName}
where ${primaryId} = ${r"#{" + "${primaryId}" + r",jdbcType=BIGINT}"}
</delete>
<!-- 查询详情 -->
<select id="selectByPrimaryKey" resultMap="BaseResultMap" parameterType="java.lang.Long">
select
<include refid="Base_Column_List"/>
from ${tableName}
where ${primaryId} = ${r"#{" + "${primaryId}" + r",jdbcType=BIGINT}"}
</select>
<!-- 按需查询 -->
<select id="selectByPrimaryKeySelective" resultMap="BaseResultMap" parameterType="${entityPackageName}.${entityName}">
select
<include refid="Base_Column_List"/>
from ${tableName}
</select>
<!-- 批量查询-->
<select id="selectByIds" resultMap="BaseResultMap" parameterType="java.util.List">
select
<include refid="Base_Column_List"/>
from ${tableName}
<where>
<if test="ids != null">
and ${primaryId} in
<foreach item="item" index="index" collection="ids" open="(" separator="," close=")">
${r"#{" + "item" + r"}"}
</foreach>
</if>
</where>
</select>
<!-- 根据条件查询 -->
<select id="selectByMap" resultMap="BaseResultMap" parameterType="java.util.Map">
select
<include refid="Base_Column_List"/>
from ${tableName}
</select>
<!-- 查询${entityName}总和 -->
<select id="countPage" resultType="int" parameterType="${dtoPackageName}.${dtoName}">
select count(${primaryId})
from ${tableName}
</select>
<!-- 查询${entityName}列表 -->
<select id="selectPage" resultMap="BaseResultMap" parameterType="${dtoPackageName}.${dtoName}">
select
<include refid="Base_Column_List"/>
from ${tableName}
limit ${r"#{" + "start,jdbcType=INTEGER" + r"}"},${r"#{" + "end,jdbcType=INTEGER" + r"}"}
</select>
</mapper>
编写dao.ftl数据访问模板
package ${daoPackageName};
import com.example.generator.core.BaseMapper;
import java.util.List;
import ${entityPackageName}.${entityName};
import ${dtoPackageName}.${dtoName};
/**
*
* @ClassName: ${daoName}
* @Description: 数据访问接口
* @author ${authorName}
* @date ${currentTime}
*
*/
public interface ${daoName} extends BaseMapper<${entityName}>{
int countPage(${dtoName} ${dtoName?uncap_first});
List<${entityName}> selectPage(${dtoName} ${dtoName?uncap_first});
}
编写service.ftl服务接口模板
package ${servicePackageName};
import com.example.generator.core.BaseService;
import com.example.generator.common.Pager;
import ${voPackageName}.${voName};
import ${dtoPackageName}.${dtoName};
import ${entityPackageName}.${entityName};
/**
*
* @ClassName: ${serviceName}
* @Description: ${entityName}业务访问接口
* @author ${authorName}
* @date ${currentTime}
*
*/
public interface ${serviceName} extends BaseService<${entityName}> {
/**
* 分页列表查询
* @param request
*/
Pager<${voName}> getPage(${dtoName} request);
}
编写serviceImpl.ftl服务实现类模板
package ${serviceImplPackageName};
import com.example.generator.common.Pager;
import com.example.generator.core.BaseServiceImpl;
import com.example.generator.test.service.TestEntityService;
import org.springframework.beans.BeanUtils;
import org.springframework.stereotype.Service;
import org.springframework.util.CollectionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.List;
import ${daoPackageName}.${daoName};
import ${entityPackageName}.${entityName};
import ${dtoPackageName}.${dtoName};
import ${voPackageName}.${voName};
@Service
public class ${serviceImplName} extends BaseServiceImpl<${daoName}, ${entityName}> implements ${serviceName} {
private static final Logger log = LoggerFactory.getLogger(${serviceImplName}.class);
/**
* 分页列表查询
* @param request
*/
public Pager<${voName}> getPage(${dtoName} request) {
List<${voName}> resultList = new ArrayList();
int count = super.baseMapper.countPage(request);
List<${entityName}> dbList = count > 0 ? super.baseMapper.selectPage(request) : new ArrayList<>();
if(!CollectionUtils.isEmpty(dbList)){
dbList.forEach(source->{
${voName} target = new ${voName}();
BeanUtils.copyProperties(source, target);
resultList.add(target);
});
}
return new Pager(request.getCurrPage(), request.getPageSize(), count, resultList);
}
}
编写controller.ftl控制层模板
package ${controllerPackageName};
import com.example.generator.common.IdRequest;
import com.example.generator.common.Pager;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.util.Objects;
import ${servicePackageName}.${serviceName};
import ${entityPackageName}.${entityName};
import ${dtoPackageName}.${dtoName};
import ${voPackageName}.${voName};
/**
*
* @ClassName: ${controllerName}
* @Description: 外部访问接口
* @author ${authorName}
* @date ${currentTime}
*
*/
@RestController
@RequestMapping("/${entityName?uncap_first}")
public class ${controllerName} {
@Autowired
private ${serviceName} ${serviceName?uncap_first};
/**
* 分页列表查询
* @param request
*/
@PostMapping(value = "/getPage")
public Pager<${voName}> getPage(@RequestBody ${dtoName} request){
return ${serviceName?uncap_first}.getPage(request);
}
/**
* 查询详情
* @param request
*/
@PostMapping(value = "/getDetail")
public ${voName} getDetail(@RequestBody IdRequest request){
${entityName} source = ${serviceName?uncap_first}.selectById(request.getId());
if(Objects.nonNull(source)){
${voName} result = new ${voName}();
BeanUtils.copyProperties(source, result);
return result;
}
return null;
}
/**
* 新增操作
* @param request
*/
@PostMapping(value = "/save")
public void save(${dtoName} request){
${entityName} entity = new ${entityName}();
BeanUtils.copyProperties(request, entity);
${serviceName?uncap_first}.insert(entity);
}
/**
* 编辑操作
* @param request
*/
@PostMapping(value = "/edit")
public void edit(${dtoName} request){
${entityName} entity = new ${entityName}();
BeanUtils.copyProperties(request, entity);
${serviceName?uncap_first}.updateById(entity);
}
/**
* 删除操作
* @param request
*/
@PostMapping(value = "/delete")
public void delete(IdRequest request){
${serviceName?uncap_first}.deleteById(request.getId());
}
}
编写entity.ftl实体类模板
package ${entityPackageName};
import java.io.Serializable;
import java.math.BigDecimal;
import java.util.Date;
/**
*
* @ClassName: ${entityName}
* @Description: ${tableDes!}实体类
* @author ${authorName}
* @date ${currentTime}
*
*/
public class ${entityName} implements Serializable {
private static final long serialVersionUID = 1L;
<#--属性遍历-->
<#list columns as pro>
<#--<#if pro.proName != primaryId
&& pro.proName != 'remarks'
&& pro.proName != 'createBy'
&& pro.proName != 'createDate'
&& pro.proName != 'updateBy'
&& pro.proName != 'updateDate'
&& pro.proName != 'delFlag'
&& pro.proName != 'currentUser'
&& pro.proName != 'page'
&& pro.proName != 'sqlMap'
&& pro.proName != 'isNewRecord'
></#if>-->
/**
* ${pro.proDes!}
*/
private ${pro.proType} ${pro.proName};
</#list>
<#--属性get||set方法-->
<#list columns as pro>
public ${pro.proType} get${pro.proName?cap_first}() {
return this.${pro.proName};
}
public ${entityName} set${pro.proName?cap_first}(${pro.proType} ${pro.proName}) {
this.${pro.proName} = ${pro.proName};
return this;
}
</#list>
}
编写dto.ftl实体类模板
package ${dtoPackageName}; import com.example.generator.core.BaseDTO; import java.io.Serializable; /** * @ClassName: ${dtoName} * @Description: 请求实体类 * @author ${authorName} * @date ${currentTime} * */ public class ${dtoName} extends BaseDTO { }编写vo.ftl视图实体类模板
package ${voPackageName}; import java.io.Serializable; /** * @ClassName: ${voName} * @Description: 返回视图实体类 * @author ${authorName} * @date ${currentTime} * */ public class ${voName} implements Serializable { private static final long serialVersionUID = 1L; }可能细心的网友已经看到了，在模板中我们用到了BaseMapper、BaseService、BaseServiceImpl等等服务类。
之所以有这三个类，是因为在模板中，我们有大量的相同的方法名包括逻辑也相似，除了所在实体类不一样以外，其他都一样，因此我们可以借助泛型类来将这些服务抽成公共的部分。
BaseMapper，主要负责将dao层的公共方法抽出来
package com.example.generator.core; import org.apache.ibatis.annotations.Param; import java.io.Serializable; import java.util.List; import java.util.Map; /** * @author pzblog * @Description * @since 2020-11-11 */ public interface BaseMapper<T> { /** * 批量插入 * @param list * @return */ int insertList(@Param("list") List<T> list); /** * 按需插入一条记录 * @param entity * @return */ int insertPrimaryKeySelective(T entity); /** * 按需修改一条记录（通过主键ID） * @return */ int updatePrimaryKeySelective(T entity); /** * 批量按需修改记录（通过主键ID） * @param list * @return */ int updateBatchByIds(@Param("list") List<T> list); /** * 根据ID删除 * @param id 主键ID * @return */ int deleteByPrimaryKey(Serializable id); /** * 根据ID查询 * @param id 主键ID * @return */ T selectByPrimaryKey(Serializable id); /** * 按需查询 * @param entity * @return */ List<T> selectByPrimaryKeySelective(T entity); /** * 批量查询 * @param ids 主键ID集合 * @return */ List<T> selectByIds(@Param("ids") List<? extends Serializable> ids); /** * 查询（根据 columnMap 条件） * @param columnMap 表字段 map 对象 * @return */ List<T> selectByMap(Map<String, Object> columnMap); }BaseService，主要负责将service层的公共方法抽出来
package com.example.generator.core; import java.io.Serializable; import java.util.List; import java.util.Map; /** * @author pzblog * @Description 服务类 * @since 2020-11-11 */ public interface BaseService<T> { /** * 新增 * @param entity * @return boolean */ boolean insert(T entity); /** * 批量新增 * @param list * @return boolean */ boolean insertList(List<T> list); /** * 通过ID修改记录（如果想全部更新，只需保证字段都不为NULL） * @param entity * @return boolean */ boolean updateById(T entity); /** * 通过ID批量修改记录（如果想全部更新，只需保证字段都不为NULL） * @param list * @return boolean */ boolean updateBatchByIds(List<T> list); /** * 根据ID删除 * @param id 主键ID * @return boolean */ boolean deleteById(Serializable id); /** * 根据ID查询 * @param id 主键ID * @return */ T selectById(Serializable id); /** * 按需查询 * @param entity * @return */ List<T> selectByPrimaryKeySelective(T entity); /** * 批量查询 * @param ids * @return */ List<T> selectByIds(List<? extends Serializable> ids); /** * 根据条件查询 * @param columnMap * @return */ List<T> selectByMap(Map<String, Object> columnMap); }BaseServiceImpl，service层的公共方法具体实现类
package com.example.generator.core; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.transaction.annotation.Transactional; import java.io.Serializable; import java.util.List; import java.util.Map; /** * @author pzblog * @Description 实现类（ 泛型说明：M 是 mapper 对象，T 是实体） * @since 2020-11-11 */ public abstract class BaseServiceImpl<M extends BaseMapper<T>, T> implements BaseService<T>{ @Autowired protected M baseMapper; /** * 新增 * @param entity * @return boolean */ @Override @Transactional(rollbackFor = {Exception.class}) public boolean insert(T entity){ return returnBool(baseMapper.insertPrimaryKeySelective(entity)); } /** * 批量新增 * @param list * @return boolean */ @Override @Transactional(rollbackFor = {Exception.class}) public boolean insertList(List<T> list){ return returnBool(baseMapper.insertList(list)); } /** * 通过ID修改记录（如果想全部更新，只需保证字段都不为NULL） * @param entity * @return boolean */ @Override @Transactional(rollbackFor = {Exception.class}) public boolean updateById(T entity){ return returnBool(baseMapper.updatePrimaryKeySelective(entity)); } /** * 通过ID批量修改记录（如果想全部更新，只需保证字段都不为NULL） * @param list * @return boolean */ @Override @Transactional(rollbackFor = {Exception.class}) public boolean updateBatchByIds(List<T> list){ return returnBool(baseMapper.updateBatchByIds(list)); } /** * 根据ID删除 * @param id 主键ID * @return boolean */ @Override @Transactional(rollbackFor = {Exception.class}) public boolean deleteById(Serializable id){ return returnBool(baseMapper.deleteByPrimaryKey(id)); } /** * 根据ID查询 * @param id 主键ID * @return */ @Override public T selectById(Serializable id){ return baseMapper.selectByPrimaryKey(id); } /** * 按需查询 * @param entity * @return */ @Override public List<T> selectByPrimaryKeySelective(T entity){ return baseMapper.selectByPrimaryKeySelective(entity); } /** * 批量查询 * @param ids * @return */ @Override public List<T> selectByIds(List<? extends Serializable> ids){ return baseMapper.selectByIds(ids); } /** * 根据条件查询 * @param columnMap * @return */ @Override public List<T> selectByMap(Map<String, Object> columnMap){ return baseMapper.selectByMap(columnMap); } /** * 判断数据库操作是否成功 * @param result 数据库操作返回影响条数 * @return boolean */ protected boolean returnBool(Integer result) { return null != result && result >= 1; } }在此，还封装来其他的类，例如 dto 公共类BaseDTO，分页类Pager，还有 id 请求类IdRequest。
BaseDTO公共类
public class BaseDTO implements Serializable { /** * 请求token */ private String token; /** * 当前页数 */ private Integer currPage = 1; /** * 每页记录数 */ private Integer pageSize = 20; /** * 分页参数（第几行） */ private Integer start; /** * 分页参数（行数） */ private Integer end; /** * 登录人ID */ private String loginUserId; /** * 登录人名称 */ private String loginUserName; public String getToken() { return token; } public BaseDTO setToken(String token) { this.token = token; return this; } public Integer getCurrPage() { return currPage; } public BaseDTO setCurrPage(Integer currPage) { this.currPage = currPage; return this; } public Integer getPageSize() { return pageSize; } public BaseDTO setPageSize(Integer pageSize) { this.pageSize = pageSize; return this; } public Integer getStart() { if (this.currPage != null && this.currPage > 0) { start = (currPage - 1) * getPageSize(); return start; } return start == null ? 0 : start; } public BaseDTO setStart(Integer start) { this.start = start; return this; } public Integer getEnd() { return getPageSize(); } public BaseDTO setEnd(Integer end) { this.end = end; return this; } public String getLoginUserId() { return loginUserId; } public BaseDTO setLoginUserId(String loginUserId) { this.loginUserId = loginUserId; return this; } public String getLoginUserName() { return loginUserName; } public BaseDTO setLoginUserName(String loginUserName) { this.loginUserName = loginUserName; return this; } }Pager分页类
public class Pager<T extends Serializable> implements Serializable { private static final long serialVersionUID = -6557244954523041805L; /** * 当前页数 */ private int currPage; /** * 每页记录数 */ private int pageSize; /** * 总页数 */ private int totalPage; /** * 总记录数 */ private int totalCount; /** * 列表数据 */ private List<T> list; public Pager(int currPage, int pageSize) { this.currPage = currPage; this.pageSize = pageSize; } public Pager(int currPage, int pageSize, int totalCount, List<T> list) { this.currPage = currPage; this.pageSize = pageSize; this.totalPage = (int) Math.ceil((double) totalCount / pageSize);; this.totalCount = totalCount; this.list = list; } public int getCurrPage() { return currPage; } public Pager setCurrPage(int currPage) { this.currPage = currPage; return this; } public int getPageSize() { return pageSize; } public Pager setPageSize(int pageSize) { this.pageSize = pageSize; return this; } public int getTotalPage() { return totalPage; } public Pager setTotalPage(int totalPage) { this.totalPage = totalPage; return this; } public int getTotalCount() { return totalCount; } public Pager setTotalCount(int totalCount) { this.totalCount = totalCount; return this; } public List<T> getList() { return list; } public Pager setList(List<T> list) { this.list = list; return this; } }IdRequest公共请求类
public class IdRequest extends BaseDTO { private Long id; public Long getId() { return id; } public IdRequest setId(Long id) { this.id = id; return this; } }2.3、编写代码生成器
前两部分主要介绍的是如何获取对应的表结构，以及代码器运行之前的准备工作。
其实代码生成器，很简单，其实就是一个main方法，没有想象中的那么复杂。
处理思路也很简单，过程如下：
1、定义基本变量，例如包名路径、模块名、表名、转换后的实体类、以及数据库连接配置，我们可以将其写入配置文件
2、读取配置文件，封装对应的模板中定义的变量
3、根据对应的模板文件和变量，生成对应的java文件
2.3.1、创建配置文件，定义变量
小编我用的是application.properties配置文件来定义变量，这个没啥规定，你也可以自定义文件名，内容如下：
#包前缀 packageNamePre=com.example.generator #模块名称 moduleName=test #表 tableName=test_db #实体类名称 entityName=TestEntity #主键ID primaryId=id #作者 authorName=pzblog #数据库名称 databaseName=yjgj_base #数据库服务器IP地址 ipName=127.0.0.1 #数据库服务器端口 portName=3306 #用户名 userName=root #密码 passWord=123456 #文件输出路径，支持自定义输出路径，如果为空，默认取当前工程的src/main/java路径 outUrl=
2.3.2、根据模板生成对应的java代码
首先，读取配置文件变量
public class SystemConstant { private static Properties properties = new Properties(); static { try { // 加载上传文件设置参数：配置文件 properties.load(SystemConstant.class.getClassLoader().getResourceAsStream("application.properties")); } catch (IOException e) { e.printStackTrace(); } } public static final String tableName = properties.getProperty("tableName"); public static final String entityName = properties.getProperty("entityName"); public static final String packageNamePre = properties.getProperty("packageNamePre"); public static final String outUrl = properties.getProperty("outUrl"); public static final String databaseName = properties.getProperty("databaseName"); public static final String ipName = properties.getProperty("ipName"); public static final String portName = properties.getProperty("portName"); public static final String userName = properties.getProperty("userName"); public static final String passWord = properties.getProperty("passWord"); public static final String authorName = properties.getProperty("authorName"); public static final String primaryId = properties.getProperty("primaryId"); public static final String moduleName = properties.getProperty("moduleName"); }然后，封装对应的模板中定义的变量
public class CodeService { public void generate(Map<String, Object> templateData) { //包前缀 String packagePreAndModuleName = getPackagePreAndModuleName(templateData); //支持对应实体插入在前面，需要带上%s templateData.put("entityPackageName", String.format(packagePreAndModuleName + ".entity", templateData.get("entityName").toString().toLowerCase())); templateData.put("dtoPackageName", String.format(packagePreAndModuleName + ".dto", templateData.get("entityName").toString().toLowerCase())); templateData.put("voPackageName", String.format(packagePreAndModuleName + ".vo", templateData.get("entityName").toString().toLowerCase())); templateData.put("daoPackageName", String.format(packagePreAndModuleName + ".dao", templateData.get("entityName").toString().toLowerCase())); templateData.put("mapperPackageName", packagePreAndModuleName + ".mapper"); templateData.put("servicePackageName", String.format(packagePreAndModuleName + ".service", templateData.get("entityName").toString().toLowerCase())); templateData.put("serviceImplPackageName", String.format(packagePreAndModuleName + ".service.impl", templateData.get("entityName").toString().toLowerCase())); templateData.put("controllerPackageName", String.format(packagePreAndModuleName + ".web", templateData.get("entityName").toString().toLowerCase())); templateData.put("apiTestPackageName", String.format(packagePreAndModuleName + ".junit", templateData.get("entityName").toString().toLowerCase())); templateData.put("currentTime", new SimpleDateFormat("yyyy-MM-dd").format(new Date())); //======================生成文件配置====================== try { // 生成Entity String entityName = String.format("%s", templateData.get("entityName").toString()); generateFile("entity.ftl", templateData, templateData.get("entityPackageName").toString(), entityName+".java"); // 生成dto String dtoName = String.format("%sDTO", templateData.get("entityName").toString()); templateData.put("dtoName", dtoName); generateFile("dto.ftl", templateData, templateData.get("dtoPackageName").toString(), dtoName + ".java"); // 生成VO String voName = String.format("%sVO", templateData.get("entityName").toString()); templateData.put("voName", voName); generateFile("vo.ftl", templateData, templateData.get("voPackageName").toString(), voName + ".java"); // 生成DAO String daoName = String.format("%sDao", templateData.get("entityName").toString()); templateData.put("daoName", daoName); generateFile("dao.ftl", templateData, templateData.get("daoPackageName").toString(), daoName + ".java"); // 生成Mapper String mapperName = String.format("%sMapper", templateData.get("entityName").toString()); generateFile("mapper.ftl", templateData, templateData.get("mapperPackageName").toString(), mapperName+".xml"); // 生成Service String serviceName = String.format("%sService", templateData.get("entityName").toString()); templateData.put("serviceName", serviceName); generateFile("service.ftl", templateData, templateData.get("servicePackageName").toString(), serviceName + ".java"); // 生成ServiceImpl String serviceImplName = String.format("%sServiceImpl", templateData.get("entityName").toString()); templateData.put("serviceImplName", serviceImplName); generateFile("serviceImpl.ftl", templateData, templateData.get("serviceImplPackageName").toString(), serviceImplName + ".java"); // 生成Controller String controllerName = String.format("%sController", templateData.get("entityName").toString()); templateData.put("controllerName", controllerName); generateFile("controller.ftl", templateData, templateData.get("controllerPackageName").toString(), controllerName + ".java"); // // 生成junit测试类 // String apiTestName = String.format("%sApiTest", templateData.get("entityName").toString()); // templateData.put("apiTestName", apiTestName); // generateFile("test.ftl", templateData, templateData.get("apiTestPackageName").toString(), // apiTestName + ".java"); } catch (Exception e) { e.printStackTrace(); } } /** * 生成文件 * @param templateName 模板名称 * @param templateData 参数名 * @param packageName 包名 * @param fileName 文件名 */ public void generateFile(String templateName, Map<String, Object> templateData, String packageName, String fileName) { templateData.put("fileName", fileName); DaseService dbService = new DaseService(templateData); // 获取数据库参数 if("entity.ftl".equals(templateName) || "mapper.ftl".equals(templateName)){ dbService.getAllColumns(templateData); } try { // 默认生成文件的路径 FreeMakerUtil freeMakerUtil = new FreeMakerUtil(); freeMakerUtil.generateFile(templateName, templateData, packageName, fileName); } catch (Exception e) { e.printStackTrace(); } } /** * 封装包名前缀 * @return */ private String getPackagePreAndModuleName(Map<String, Object> templateData){ String packageNamePre = templateData.get("packageNamePre").toString(); String moduleName = templateData.get("moduleName").toString(); if(StringUtils.isNotBlank(moduleName)){ return packageNamePre + "." + moduleName; } return packageNamePre; } }接着，获取模板文件，并生成相应的模板文件
public class FreeMakerUtil { /** * 根据Freemark模板，生成文件 * @param templateName:模板名 * @param root：数据原型 * @throws Exception */ public void generateFile(String templateName, Map<String, Object> root, String packageName, String fileName) throws Exception { FileOutputStream fos=null; Writer out =null; try { // 通过一个文件输出流，就可以写到相应的文件中，此处用的是绝对路径 String entityName = (String) root.get("entityName"); String fileFullName = String.format(fileName, entityName); packageName = String.format(packageName, entityName.toLowerCase()); String fileStylePackageName = packageName.replaceAll("\\.", "/"); File file = new File(root.get("outUrl").toString() + "/" + fileStylePackageName + "/" + fileFullName); if (!file.getParentFile().exists()) { file.getParentFile().mkdirs(); } file.createNewFile(); Template template = getTemplate(templateName); fos = new FileOutputStream(file); out = new OutputStreamWriter(fos); template.process(root, out); out.flush(); } catch (Exception e) { e.printStackTrace(); } finally { try { if (fos != null){ fos.close(); } if(out != null){ out.close(); } } catch (IOException e) { e.printStackTrace(); } } } /** * * 获取模板文件 * * @param name * @return */ public Template getTemplate(String name) { try { Configuration cfg = new Configuration(Configuration.VERSION_2_3_23); cfg.setClassForTemplateLoading(this.getClass(), "/ftl"); Template template = cfg.getTemplate(name); return template; } catch (IOException e) { e.printStackTrace(); } return null; } }最后，我们编写一个main方法，看看运行之后的效果
public class GeneratorMain { public static void main(String[] args) { System.out.println("生成代码start......"); //获取页面或者配置文件的参数 Map<String, Object> templateData = new HashMap<String, Object>(); templateData.put("tableName", SystemConstant.tableName); System.out.println("表名=="+ SystemConstant.tableName); templateData.put("entityName", SystemConstant.entityName); System.out.println("实体类名称=="+ SystemConstant.entityName); templateData.put("packageNamePre", SystemConstant.packageNamePre); System.out.println("包名前缀=="+ SystemConstant.packageNamePre); //支持自定义输出路径 if(StringUtils.isNotBlank(SystemConstant.outUrl)){ templateData.put("outUrl", SystemConstant.outUrl); } else { String path = GeneratorMain.class.getClassLoader().getResource("").getPath() + "../../src/main/java"; templateData.put("outUrl", path); } System.out.println("生成文件路径为=="+ templateData.get("outUrl")); templateData.put("authorName", SystemConstant.authorName); System.out.println("以后代码出问题找=="+ SystemConstant.authorName); templateData.put("databaseName", SystemConstant.databaseName); templateData.put("ipName", SystemConstant.ipName); templateData.put("portName", SystemConstant.portName); templateData.put("userName", SystemConstant.userName); templateData.put("passWord", SystemConstant.passWord); //主键ID templateData.put("primaryId", SystemConstant.primaryId); //模块名称 templateData.put("moduleName", SystemConstant.moduleName); CodeService dataService = new CodeService(); try { //生成代码文件 dataService.generate(templateData); } catch (Exception e) { e.printStackTrace(); } System.out.println("生成代码end......"); } }结果如下：
生成的 Controller 层代码如下
/** * * @ClassName: TestEntityController * @Description: 外部访问接口 * @author pzblog * @date 2020-11-16 * */ @RestController @RequestMapping("/testEntity") public class TestEntityController { @Autowired private TestEntityService testEntityService; /** * 分页列表查询 * @param request */ @PostMapping(value = "/getPage") public Pager<TestEntityVO> getPage(@RequestBody TestEntityDTO request){ return testEntityService.getPage(request); } /** * 查询详情 * @param request */ @PostMapping(value = "/getDetail") public TestEntityVO getDetail(@RequestBody IdRequest request){ TestEntity source = testEntityService.selectById(request.getId()); if(Objects.nonNull(source)){ TestEntityVO result = new TestEntityVO(); BeanUtils.copyProperties(source, result); return result; } return null; } /** * 新增操作 * @param request */ @PostMapping(value = "/save") public void save(TestEntityDTO request){ TestEntity entity = new TestEntity(); BeanUtils.copyProperties(request, entity); testEntityService.insert(entity); } /** * 编辑操作 * @param request */ @PostMapping(value = "/edit") public void edit(TestEntityDTO request){ TestEntity entity = new TestEntity(); BeanUtils.copyProperties(request, entity); testEntityService.updateById(entity); } /** * 删除操作 * @param request */ @PostMapping(value = "/delete") public void delete(IdRequest request){ testEntityService.deleteById(request.getId()); } }至此，一张单表的90%的基础工作量全部开发完毕!
三、总结
代码生成器，在实际的项目开发中应用非常的广，本文主要以freemaker模板引擎为基础，开发的一套全自动代码生成器，一张单表的CRUD，只需要5秒钟就可以完成!
最后多说一句，如果你是项目负责人，那么代码生成器会是一个比较好的提升项目开发效率的工具，希望能帮到各位!
