SpringBoot+MyBatis-Plus+Velocity实现代码自动生成

目录

• 1. 前提条件
• 2. 代码生成器设计
• 2.1 配置代码生成器
• 2.2 Velocity 模板
• 3. 运行生成代码
• 4. 测试接口
• 5. 总结

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<Sphptring, 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 = ?";
            Lis编程t<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", sqlTypephpToJavaType(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.编程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 ${tablejavascriptComment}")
    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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