简介

:::info 企业追求敏捷开发自然离不开低代码平台.低代码平台的常见能力,如:模型编排,流程编排.服务编排,界面编排等.其实低代码就是对共性抽取,对特性扩展.使得开发人员专注于业务的开发.
那一键生成代码怎么做?

正向工程:就是通过可视化界面等创建表到生成crud (推荐若依开源框架https://gitee.com/y_project/RuoYi/tree/master/ruoyi-generator)
逆向工程:通过已知表,直接生成crud ::: 需求:输入表名自动生成crud代码?(逆向工程)
实现:

通过表名,去数据库查询表信息(如:表注释),表字段信息(如:字段名,字段类型,字段注释等)
然后通过模板引擎去生成代码

实现逆向工程

mysql为例:数据表以及字段信息需要如下sql

--显示user表所有字段
SHOW FULL COLUMNS FROM user;
select COLUMN_NAME, DATA_TYPE, COLUMN_COMMENT
from information_schema.columns
where TABLE_NAME = 'user';
select COLUMN_NAME, DATA_TYPE, COLUMN_COMMENT
from information_schema.COLUMNS
where table_name = 'user'
  and table_schema = 'spring_db';
select TABLE_NAME, TABLE_COMMENT
from information_schema.TABLES
where table_schema = 'spring_db'
  and table_name = 'user';

创建springboot项目引入如下依赖


<dependencies>
  <dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <scope>runtime</scope>
  </dependency>
  <dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.2</version>
  </dependency>
  <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <scope>test</scope>
  </dependency>
  <!--velocity代码生成使用模板 -->
  <dependency>
    <groupId>org.apache.velocity</groupId>
    <artifactId>velocity-engine-core</artifactId>
    <version>2.3</version>
  </dependency>
  <!-- 阿里JSON解析器 -->
  <dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.83</version>
  </dependency>
</dependencies>

application.yml

server:
  port: 8080
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/spring_db?characterEncoding=utf-8&useSSL=false&serverTimezone=GMT%2B8
    username: root
    password: 123456
    type: com.zaxxer.hikari.HikariDataSource
    hikari:
      connection-timeout: 30000
      idle-timeout: 30000
      auto-commit: 'true'
      minimum-idle: 5
      maximum-pool-size: 15
      pool-name: HikariCP
      connection-test-query: SELECT 1 FROM DUAL
      max-lifetime: 1800000
mybatis-plus:
  mapper-locations: classpath*:mybatis/mapper/*.xml
  type-aliases-package: com.itmck.pojo
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl

表字段信息实体

package com.itmck.ormgeneratortool.dao.entity;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;
@Data
@TableName("information_schema.columns")
public class ColumnInformation {
    /**
     * field名
     */
    @TableField("columnName")
    private String columnName;
    /**
     * 类型
     */
    @TableField("dataType")
    private String dataType;
    /**
     * 注释
     */
    @TableField("columnComment")
    private String columnComment;
}

数据表信息实体

package com.itmck.ormgeneratortool.dao.entity;
import lombok.Data;
import lombok.experimental.Accessors;
import javax.validation.Valid;
import javax.validation.constraints.NotBlank;
import java.util.List;
/**
 * 业务表 gen_table
 *
 * @author ruoyi
 */
@Data
@Accessors(chain = true)
public class TableInformation {
    private static final long serialVersionUID = 1L;
    /**
     * 表名称
     */
    private String tableName;
    /**
     * 表描述
     */
    private String tableComment;
}

mapper

package com.itmck.ormgeneratortool.dao.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.itmck.ormgeneratortool.dao.entity.ColumnInformation;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import java.util.List;
@Mapper
public interface ColumnInformationMapper extends BaseMapper<ColumnInformation> {
    @Select(value = "select COLUMN_NAME, DATA_TYPE, COLUMN_COMMENT from information_schema.COLUMNS where table_name = #{tableName} and table_schema = #{dbName}")
    List<ColumnInformation> showColumns(@Param("tableName") String tableName, @Param("dbName") String dbName);
}

package com.itmck.ormgeneratortool.dao.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.itmck.ormgeneratortool.dao.entity.TableInformation;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
@Mapper
public interface TableInformationMapper extends BaseMapper<TableInformation> {
    @Select(value = "select TABLE_NAME,TABLE_COMMENT from information_schema.TABLES where table_schema = #{tableSchema} and table_name =#{tableName}")
    TableInformation showTableInformation(@Param("tableName") String tableName, @Param("tableSchema") String tableSchema);
}

其实到这里就可以查出表的信息以及字段信息.剩下的就是将查询出来的信息填充到模板引擎对应的变量位置.

其余代码这里就不贴出来,后续参考我git[https://gitee.com/itmc/orm-generator-tool.git]

Java 实战入门

如何手动实现逆向工程?

简介

实现逆向工程