背景
基于 MyBatis 开发的项目，新增数据库表以后，总是需要编写对应的 Entity、Mapper 和 Service 等等 Class 的代码，这些都是重复的工作，我们可以想一些办法来自动生成这些代码。
方案
一种可选的方案是使用 MyBatis Generator，官方支持，常见需求一般也都能满足。但是它的配置文件比较繁琐，如果有一些项目相关的个性化需求，不一定很好处理。
这里介绍另外一种我觉得更为简便灵活的方法。
近几年版本的 IDEA 里已经自带了 Database Tools and SQL 插件，可以连接数据库进行常用的操作，并且，它还自带了数据库表对应 POJO 类的代码生成器：在 Database 面板里配置好数据源以后，右键表名，依次选择 Scripted Extensions、Generate POJOs.groovy，选择生成路径后，即可生成对应的 Entity 类。
既然能够生成 Entity，那么我们可以基于它进行修改，让它一次性生成我们需要的 Entity、Mapper 和 Service。
需求
基于项目情况，我们对生成的代码有如下要求：
Entity 需要继承指定基类，数据库表的公共字段放在基类里；
Mapper、Service 和 ServiceImpl 分别需要实现指定的类继承关系；
Entity、Mapper 和 Service 需要自动放在对应的子包下。
以 t_promotion_channel 表为例，指定该表和对应的代码目录之后，生成的目录结构如下：
.
├── entity
│ └── PromotionChannel.java
├── mapper
│ └── PromotionChannelMapper.java
└── service
├── PromotionChannelService.java
└── impl
└── PromotionChannelServiceImpl.java
需要生成的代码如下：
entity/PromotionChannel.java
package com.test.data.promotion.entity;
import com.test.common.base.BaseEntity;
import lombok.Data;
import lombok.EqualsAndHashCode;
import javax.persistence.Table;
/**
* @author mazhuang
*/
@EqualsAndHashCode(callSuper = true)
@Data
@Table(name = "t_promotion_channel")
public class PromotionChannel extends BaseEntity {
private static final long serialVersionUID = 5495175453870776988L;
/**
* 用户ID
*/
private Long fkUserId;
/**
* 渠道名称
*/
private String channelName;
}
mapper/PromotionChannelMapper.java
package com.test.data.promotion.mapper;
import com.test.common.base.BaseMapper;
import com.test.data.promotion.entity.PromotionChannel;
/**
* @author mazhuang
*/
public interface PromotionChannelMapper extends BaseMapper<PromotionChannel> {
}
service/PromotionChannelService.java
package com.test.data.promotion.service;
import com.test.common.base.BaseService;
import com.test.data.promotion.entity.PromotionChannel;
/**
* @author mazhuang
*/
public interface PromotionChannelService extends BaseService<PromotionChannel> {
}
service/impl/PromotionChannelServiceImpl.java
package com.test.data.promotion.service.impl;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import com.test.common.base.BaseServiceImpl;
import com.test.data.promotion.entity.PromotionChannel;
import com.test.data.promotion.mapper.PromotionChannelMapper;
import com.test.data.promotion.service.PromotionChannelService;
/**
* @author mazhuang
*/
@Slf4j
@Service
public class PromotionChannelServiceImpl extends BaseServiceImpl<PromotionChannelMapper, PromotionChannel> implements PromotionChannelService {
}
实现
右键一个数据库表，依次选择 Scripted Extensions、Go to Scripts Directory，进入生成的脚本目录，找到 Generate POJOs.groovy，复制一份，重命名为 Generate MyBatis Code.groovy，然后修改内容如下：
import com.intellij.database.model.DasTable
import com.intellij.database.util.Case
import com.intellij.database.util.DasUtil
/*
* Available context bindings:
* SELECTION Iterable<DasObject>
* PROJECT project
* FILES files helper
*/
typeMapping = [
(~/(?i)int/) : "Long",
(~/(?i)float|double|decimal|real/): "BigDecimal",
(~/(?i)datetime|timestamp/) : "java.util.Date",
(~/(?i)date/) : "java.sql.Date",
(~/(?i)time/) : "java.sql.Time",
(~/(?i)/) : "String"
]
FILES.chooseDirectoryAndSave("Choose directory", "Choose where to store generated files") { dir ->
SELECTION.filter { it instanceof DasTable }.each { generate(it, dir) }
}
def generate(table, dir) {
def className = javaName(table.getName().replaceFirst('t_', ''), true)
def fields = calcFields(table)
dirPath = dir.getAbsolutePath()
packageName = calcPackageName(dirPath)
// Generate POJO
new File(dirPath + File.separator + "entity", className + ".java").withPrintWriter("utf-8") { out -> generateEntity(out, table.getName(), className, fields, packageName) }
// Generate Mapper
new File(dirPath + File.separator + "mapper", className + "Mapper.java").withPrintWriter("utf-8") { out -> generateMapper(out, className, packageName) }
// Generate Service
new File(dirPath + File.separator + "service", className + "Service.java").withPrintWriter("utf-8") { out -> generateService(out, className, packageName) }
// Generate ServiceImpl
new File(dirPath + File.separator + "service" + File.separator + "impl", className + "ServiceImpl.java").withPrintWriter("utf-8") { out -> generateServiceImpl(out, className, packageName) }
}
static def generateEntity(out, tableName, className, fields, packageName) {
out.println "package $packageName" + ".entity;"
out.println ""
out.println "import com.test.common.base.BaseEntity;"
out.println "import lombok.Data;"
out.println "import lombok.EqualsAndHashCode;"
out.println "import javax.persistence.Table;"
out.println ""
out.println "/**\n * @author mazhuang\n */"
out.println "@EqualsAndHashCode(callSuper = true)"
out.println "@Data"
out.println "@Table(name = \"$tableName\")"
out.println "public class $className extends BaseEntity {"
out.println ""
def baseEntityFields = ['pkid', 'addedBy', 'addedTime', 'lastModifiedBy', 'lastModifiedTime', 'valid']
fields.each() {
if (baseEntityFields.contains(it.name)) {
return
}
if (it.annos != "") out.println " ${it.annos}"
if (it.comment != null) out.println " /**\n * ${it.comment}\n */"
out.println " private ${it.type}${it.name};\n"
}
out.println "}"
}
static def generateMapper(out, className, packageName) {
out.println "package $packageName" + ".mapper;"
out.println ""
out.println "import com.test.common.base.BaseMapper;"
out.println "import $packageName" + ".entity.$className;"
out.println ""
out.println "/**\n * @author mazhuang\n */"
out.println "public interface $className" + "Mapper extends BaseMapper<$className> {"
out.println ""
out.println "}"
}
static def generateService(out, className, packageName) {
out.println "package $packageName" + ".service;"
out.println ""
out.println "import com.test.common.base.BaseService;"
out.println "import $packageName" + ".entity.$className;"
out.println ""
out.println "/**\n * @author mazhuang\n */"
out.println "public interface $className" + "Service extends BaseService<$className> {"
out.println ""
out.println "}"
}
static def generateServiceImpl(out, className, packageName) {
out.println "package $packageName" + ".service.impl;"
out.println ""
out.println "import lombok.extern.slf4j.Slf4j;"
out.println "import org.springframework.stereotype.Service;"
out.println "import com.test.common.base.BaseServiceImpl;"
out.println "import $packageName" + ".entity.$className;"
out.println "import $packageName" + ".mapper.$className" + "Mapper;"
out.println "import $packageName" + ".service.$className" + "Service;"
out.println ""
out.println "/**\n * @author mazhuang\n */"
out.println "@Slf4j"
out.println "@Service"
out.println "public class $className" + "ServiceImpl extends BaseServiceImpl<$className" + "Mapper, $className> implements $className" + "Service {"
out.println ""
out.println "}"
}
def calcFields(table) {
DasUtil.getColumns(table).reduce([]) {
fields, col ->
def spec = Case.LOWER.apply(col.getDataType().getSpecification())
def typeStr = typeMapping.find { p, t -> p.matcher(spec).find() }.value
fields += [[
name : javaName(col.getName(), false),
type : typeStr,
comment: col.getComment(), // 注释
default: col.getDefault(), // 默认值
annos : ""]]
}
}
static def calcPackageName(dirPath) {
def startPos = dirPath.indexOf('com')
return dirPath.substring(startPos).replaceAll(File.separator, ".")
}
def javaName(str, capitalize) {
def s = com.intellij.psi.codeStyle.NameUtil.splitNameIntoWords(str)
.collect { Case.LOWER.apply(it).capitalize() }
.join("")
.replaceAll(/[^\p{javaJavaIdentifierPart}[_]]/, "_")
capitalize || s.length() == 1 ? s : Case.LOWER.apply(s[0]) + s[1..-1]
}
大功告成，现在右键一个数据库表，依次选择 Scripted Extensions、Generate MyBatis Code.groovy，在弹出的目录选择框里选择想要放置代码的目录，即可生成期望的模板代码了。
后续如果有一些个性化的代码生成需求，可以根据实际情况修改、新增脚本来完成。
其它
本文代码生成器脚本已上传至 GitHub，仓库地址：https://github.com/mzlogin/code-generator ，以后如果有更新，或者新的代码生成脚本，也会放在这个仓库里。
