我要评论1. 前提条件
开发环境：
- spring boot 2.x
- mybatis-plus
- lombok
- swagger & knife4j
- velocity 模板引擎
- 数据库（mysql）
所需依赖：
在 pom.xml 中加入以下依赖：
<dependencies>
<!-- spring boot web -->
<dependency>
<groupid>org.springframework.boot</groupid>
<artifactid>spring-boot-starter-web</artifactid>
</dependency>
<!-- mybatis-plus -->
<dependency>
<groupid>com.baomidou</groupid>
<artifactid>mybatis-plus-boot-starter</artifactid>
<version>3.4.0</version>
</dependency>
<!-- lombok -->
<dependency>
<groupid>org.projectlombok</groupid>
<artifactid>lombok</artifactid>
<version>1.18.24</version>
<scope>provided</scope>
</dependency>
<!-- swagger -->
<dependency>
<groupid>io.swagger</groupid>
<artifactid>swagger-annotations</artifactid>
<version>1.6.0</version>
</dependency>
<!-- knife4j -->
<dependency>
<groupid>com.github.xiaoymin</groupid>
<artifactid>knife4j-springdoc-ui</artifactid>
<version>2.0.6</version>
</dependency>
<!-- velocity -->
<dependency>
<groupid>org.apache.velocity</groupid>
<artifactid>velocity-engine-core</artifactid>
<version>2.3</version>
</dependency>
</dependencies>
2. 代码生成器设计
接下来我们创建一个 代码生成器，该生成器能够通过查询数据库的表信息并生成相应的代码。
2.1 配置代码生成器
在 codegenerator.java 中，编写生成代码的逻辑。主要是从数据库读取表结构信息，并通过 velocity 模板生成对应的实体类、mapper、service、controller 等代码。
package com.example.demo.generator;
import java.sql.*;
import java.util.*;
public class codegenerator {
public static void main(string[] args) {
// 配置数据库连接
string url = "jdbc:mysql://localhost:3306/your_database";
string username = "root";
string password = "password";
string database = "your_database";
string tablename = "your_table";
// 获取表信息并生成代码
map<string, object> tableinfo = gettableinfo(url, username, password, database, tablename);
generatecode(tableinfo);
}
public static map<string, object> gettableinfo(string url, string username, string password, string database, string tablename) {
map<string, object> map = new hashmap<>();
try (connection conn = drivermanager.getconnection(url, username, password)) {
// 查询表注释
string tablequery = "select table_comment from information_schema.tables where table_schema = ? and table_name = ?";
try (preparedstatement ps = conn.preparestatement(tablequery)) {
ps.setstring(1, database);
ps.setstring(2, tablename);
resultset rs = ps.executequery();
if (rs.next()) {
map.put("tablecomment", rs.getstring("table_comment"));
}
}
// 查询字段信息
string columnquery = "select column_name, column_type, column_comment from information_schema.columns where table_schema = ? and table_name = ?";
list<map<string, string>> columns = new arraylist<>();
try (preparedstatement ps = conn.preparestatement(columnquery)) {
ps.setstring(1, database);
ps.setstring(2, tablename);
resultset rs = ps.executequery();
while (rs.next()) {
map<string, string> columninfo = new hashmap<>();
columninfo.put("columnname", rs.getstring("column_name"));
columninfo.put("javaname", tocamelcase(rs.getstring("column_name"))); // 转换为 java 变量名
columninfo.put("javatype", sqltypetojavatype(rs.getstring("column_type"))); // 转换为 java 类型
columninfo.put("comment", rs.getstring("column_comment"));
columns.add(columninfo);
}
}
map.put("columns", columns);
map.put("tablename", tablename);
map.put("entityname", tocamelcase(tablename));
} catch (sqlexception e) {
e.printstacktrace();
}
return map;
}
private static string sqltypetojavatype(string sqltype) {
sqltype = sqltype.tolowercase();
if (sqltype.contains("int")) {
return "integer";
} else if (sqltype.contains("bigint")) {
return "long";
} else if (sqltype.contains("char") || sqltype.contains("text") || sqltype.contains("varchar")) {
return "string";
} else if (sqltype.contains("datetime") || sqltype.contains("timestamp")) {
return "localdatetime";
} else if (sqltype.contains("date")) {
return "localdate";
} else if (sqltype.contains("decimal") || sqltype.contains("double")) {
return "bigdecimal";
} else {
return "string";
}
}
private static string tocamelcase(string name) {
stringbuilder result = new stringbuilder();
string[] parts = name.split("_");
for (int i = 0; i < parts.length; i++) {
if (i == 0) {
result.append(parts[i].tolowercase());
} else {
result.append(character.touppercase(parts[i].charat(0))).append(parts[i].substring(1).tolowercase());
}
}
return result.tostring();
}
private static void generatecode(map<string, object> tableinfo) {
// 读取表信息
string entityname = (string) tableinfo.get("entityname");
string tablename = (string) tableinfo.get("tablename");
string tablecomment = (string) tableinfo.get("tablecomment");
list<map<string, string>> columns = (list<map<string, string>>) tableinfo.get("columns");
// 设置 velocity 配置
velocityengine velocityengine = new velocityengine();
velocityengine.init();
// 配置模板目录
string templatedir = "path/to/your/templates"; // 模板文件的路径
// 设置输出目录
string outputdir = "path/to/output"; // 输出的代码文件夹路径
// 创建 velocity 上下文
velocitycontext context = new velocitycontext();
context.put("package", "com.example"); // 设置包路径
context.put("entityname", entityname);
context.put("tablename", tablename);
context.put("tablecomment", tablecomment);
context.put("columns", columns);
// 生成 entity 文件
generatefile(velocityengine, context, templatedir, "entity.vm", outputdir + "/entity/" + entityname + ".java");
// 生成 mapper 文件
generatefile(velocityengine, context, templatedir, "mapper.vm", outputdir + "/mapper/" + entityname + "mapper.java");
// 生成 service 接口文件
generatefile(velocityengine, context, templatedir, "service.vm", outputdir + "/service/" + entityname + "service.java");
// 生成 serviceimpl 文件
generatefile(velocityengine, context, templatedir, "serviceimpl.vm", outputdir + "/service/impl/" + entityname + "serviceimpl.java");
// 生成 controller 文件
generatefile(velocityengine, context, templatedir, "controller.vm", outputdir + "/controller/" + entityname + "controller.java");
}
private static void generatefile(velocityengine velocityengine, velocitycontext context, string templatedir, string templatename, string outputfilepath) {
// 获取模板
template template = velocityengine.gettemplate(templatedir + "/" + templatename);
// 创建文件输出流
try (filewriter writer = new filewriter(outputfilepath)) {
// 将上下文数据渲染到模板中
template.merge(context, writer);
} catch (ioexception e) {
e.printstacktrace();
}
}
}
2.2 velocity 模板
entity 模板（entity.vm）
package ${package.entity};
import com.baomidou.mybatisplus.annotation.tableid;
import com.baomidou.mybatisplus.annotation.tablename;
import lombok.data;
import io.swagger.annotations.apimodel;
import io.swagger.annotations.apimodelproperty;
import java.io.serializable;
import java.time.localdate;
import java.time.localdatetime;
import java.math.bigdecimal;
@data
@tablename("${tablename}")
@apimodel(value = "${entityname} 实体")
public class ${entityname} implements serializable {
private static final long serialversionuid = 1l;
@tableid
@apimodelproperty("主键id")
private long id;
#foreach ($column in $columns)
@apimodelproperty("${column.comment}")
private ${column.javatype} ${column.javaname};
#end
}
mapper 模板（mapper.vm）
package ${package.mapper};
import com.baomidou.mybatisplus.core.mapper.basemapper;
import ${package.entity}.${entityname};
import org.apache.ibatis.annotations.mapper;
@mapper
public interface ${entityname}mapper extends basemapper<${entityname}> {
}
service 模板（service.vm）
package ${package.service};
import ${package.entity}.${entityname};
import com.baomidou.mybatisplus.extension.service.iservice;
public interface ${entityname}service extends iservice<${entityname}> {
}
serviceimpl 模板（serviceimpl.vm）
package ${package.serviceimpl};
import ${package.entity}.${entityname};
import ${package.mapper}.${entityname}mapper;
import ${package.service}.${entityname}service;
import com.baomidou.mybatisplus.extension.service.impl.serviceimpl;
import org.springframework.stereotype.service;
@service
public class ${entityname}serviceimpl extends serviceimpl<${entityname}mapper, ${entityname}> implements ${entityname}service {
}
controller 模板（controller.vm）
package ${package.controller};
import ${package.entity}.${entityname};
import ${package.service}.${entityname}service;
import org.springframework.web.bind.annotation.*;
import io.swagger.annotations.api;
import io.swagger.annotations.apioperation;
import javax.annotation.resource;
import java.util.list;
@restcontroller
@requestmapping("/${tablename}")
@api(tags = "${tablecomment}")
public class ${entityname}controller {
@resource
private ${entityname}service service;
@getmapping("/list")
@apioperation("获取所有 ${tablecomment}")
public list<${entityname}> list() {
return service.list();
}
@postmapping("/add")
@apioperation("新增 ${tablecomment}")
public boolean add(@requestbody ${entityname} entity) {
return service.save(entity);
}
@putmapping("/update")
@apioperation("更新 ${tablecomment}")
public boolean update(@requestbody ${entityname} entity) {
return service.updatebyid(entity);
}
@deletemapping("/delete/{id}")
@apioperation("删除 ${tablecomment}")
public boolean delete(@pathvariable long id) {
return service.removebyid(id);
}
}
3. 运行生成代码
- 启动 spring boot 项目，配置好数据库连接。
- 运行
codegenerator.java，自动从数据库中读取表信息，并生成相应的代码。 - 查看生成的代码：
- 实体类：包含数据库表字段的实体类代码。
- mapper、service、serviceimpl、controller：自动生成增删改查接口和实现。
4. 测试接口
启动项目后，使用 swagger ui 进行接口测试。访问 http://localhost:8080/doc.html 可以看到自动生成的接口文档，通过 swagger 的 ui 直接进行增删改查操作。
5. 总结
通过本教程，我们利用 spring boot、mybatis-plus 和 velocity 模板引擎 实现了一个自动化的代码生成器，能够根据数据库表结构自动生成增删改查操作的代码，并且集成了 lombok、swagger 和 knife4j，极大地提高了开发效率。
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