SpringBoot+MyBatis-Plus+Velocity implements automatic code generation

1. Prerequisites

Development environment:

Spring Boot
MyBatis-Plus
Lombok
Swagger & Knife4j
Velocity template engine
Database (MySQL)

Required dependencies:

existAdd the following dependencies:

<dependencies>
    <!-- Spring Boot Web -->
    <dependency>
        <groupId></groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>

    <!-- MyBatis-Plus -->
    <dependency>
        <groupId></groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.4.0</version>
    </dependency>

    <!-- Lombok -->
    <dependency>
        <groupId></groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.24</version>
        <scope>provided</scope>
    </dependency>

    <!-- Swagger -->
    <dependency>
        <groupId></groupId>
        <artifactId>swagger-annotations</artifactId>
        <version>1.6.0</version>
    </dependency>

    <!-- Knife4j -->
    <dependency>
        <groupId></groupId>
        <artifactId>knife4j-springdoc-ui</artifactId>
        <version>2.0.6</version>
    </dependency>

    <!-- Velocity -->
    <dependency>
        <groupId></groupId>
        <artifactId>velocity-engine-core</artifactId>
        <version>2.3</version>
    </dependency>
</dependencies>

2. Code generator design

Next we create a code generator that can query the table information of the database and generate corresponding code.

2.1 Configuring the Code Generator

exist, write the logic to generate code. It mainly reads table structure information from the database and generates corresponding entity classes, Mappers, Services, Controllers and other codes through Velocity templates.

package ;

import .*;
import .*;

public class CodeGenerator {
    public static void main(String[] args) {
        // Configure database connection        String url = "jdbc:mysql://localhost:3306/your_database";
        String username = "root";
        String password = "password";
        String database = "your_database";
        String tableName = "your_table";

        // Get table information and generate code        Map&lt;String, Object&gt; tableInfo = getTableInfo(url, username, password, database, tableName);
        generateCode(tableInfo);
    }

    public static Map&lt;String, Object&gt; getTableInfo(String url, String username, String password, String database, String tableName) {
        Map&lt;String, Object&gt; map = new HashMap&lt;&gt;();
        try (Connection conn = (url, username, password)) {
            // Query table comments            String tableQuery = "SELECT table_comment FROM information_schema.tables WHERE table_schema = ? AND table_name = ?";
            try (PreparedStatement ps = (tableQuery)) {
                (1, database);
                (2, tableName);
                ResultSet rs = ();
                if (()) {
                    ("tableComment", ("table_comment"));
                }
            }

            // Query field information            String columnQuery = "SELECT column_name, column_type, column_comment FROM information_schema.columns WHERE table_schema = ? AND table_name = ?";
            List&lt;Map&lt;String, String&gt;&gt; columns = new ArrayList&lt;&gt;();
            try (PreparedStatement ps = (columnQuery)) {
                (1, database);
                (2, tableName);
                ResultSet rs = ();
                while (()) {
                    Map&lt;String, String&gt; columnInfo = new HashMap&lt;&gt;();
                    ("columnName", ("column_name"));
                    ("javaName", toCamelCase(("column_name")));  // Convert to Java variable name                    ("javaType", sqlTypeToJavaType(("column_type")));  // Convert to Java type                    ("comment", ("column_comment"));
                    (columnInfo);
                }
            }
            ("columns", columns);
            ("tableName", tableName);
            ("entityName", toCamelCase(tableName));
        } catch (SQLException e) {
            ();
        }
        return map;
    }

    private static String sqlTypeToJavaType(String sqlType) {
        sqlType = ();
        if (("int")) {
            return "Integer";
        } else if (("bigint")) {
            return "Long";
        } else if (("char") || ("text") || ("varchar")) {
            return "String";
        } else if (("datetime") || ("timestamp")) {
            return "LocalDateTime";
        } else if (("date")) {
            return "LocalDate";
        } else if (("decimal") || ("double")) {
            return "BigDecimal";
        } else {
            return "String";
        }
    }

    private static String toCamelCase(String name) {
        StringBuilder result = new StringBuilder();
        String[] parts = ("_");
        for (int i = 0; i &lt; ; i++) {
            if (i == 0) {
                (parts[i].toLowerCase());
            } else {
                ((parts[i].charAt(0))).append(parts[i].substring(1).toLowerCase());
            }
        }
        return ();
    }
private static void generateCode(Map&lt;String, Object&gt; tableInfo) {
    // Read table information    String entityName = (String) ("entityName");
    String tableName = (String) ("tableName");
    String tableComment = (String) ("tableComment");
    List&lt;Map&lt;String, String&gt;&gt; columns = (List&lt;Map&lt;String, String&gt;&gt;) ("columns");

    // Set Velocity configuration    VelocityEngine velocityEngine = new VelocityEngine();
    ();

    //Configuration template directory    String templateDir = "path/to/your/templates"; // The path to the template file
    // Set the output directory    String outputDir = "path/to/output"; // Output code folder path
    // Create Velocity context    VelocityContext context = new VelocityContext();
    ("package", ""); // Set the package path    ("entityName", entityName);
    ("tableName", tableName);
    ("tableComment", tableComment);
    ("columns", columns);

    // Generate Entity file    generateFile(velocityEngine, context, templateDir, "", outputDir + "/entity/" + entityName + ".java");

    // Generate Mapper file    generateFile(velocityEngine, context, templateDir, "", outputDir + "/mapper/" + entityName + "");

    // Generate Service interface file    generateFile(velocityEngine, context, templateDir, "", outputDir + "/service/" + entityName + "");

    // Generate ServiceImpl file    generateFile(velocityEngine, context, templateDir, "", outputDir + "/service/impl/" + entityName + "");

    // Generate Controller file    generateFile(velocityEngine, context, templateDir, "", outputDir + "/controller/" + entityName + "");
}

	private static void generateFile(VelocityEngine velocityEngine, VelocityContext context, String templateDir, String templateName, String outputFilePath) {
	    // Get the template	    Template template = (templateDir + "/" + templateName);
	
	    // Create file output stream	    try (FileWriter writer = new FileWriter(outputFilePath)) {
	        // Render context data into template	        (context, writer);
	    } catch (IOException e) {
	        ();
	    }
	}

}

2.2 Velocity template

Entity template()

package ${};

import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;
import ;

@Data
@TableName("${tableName}")
@ApiModel(value = "${entityName} entity")
public class ${entityName} implements Serializable {

    private static final long serialVersionUID = 1L;

    @TableId
    @ApiModelProperty("Primary Key ID")
    private Long id;

#foreach ($column in $columns)
    @ApiModelProperty("${}")
    private ${} ${};
#end
}

Mapper template ()

package ${};

import ;
import ${}.${entityName};
import ;

@Mapper
public interface ${entityName}Mapper extends BaseMapper<${entityName}> {
}

Service template ()

package ${};

import ${}.${entityName};
import ;

public interface ${entityName}Service extends IService<${entityName}> {
}

ServiceImpl Template ()

package ${};

import ${}.${entityName};
import ${}.${entityName}Mapper;
import ${}.${entityName}Service;
import ;
import ;

@Service
public class ${entityName}ServiceImpl extends ServiceImpl<${entityName}Mapper, ${entityName}> implements ${entityName}Service {
}

Controller template()

package ${};

import ${}.${entityName};
import ${}.${entityName}Service;
import .*;
import ;
import ;
import ;
import ;

@RestController
@RequestMapping("/${tableName}")
@Api(tags = "${tableComment}")
public class ${entityName}Controller {

    @Resource
    private ${entityName}Service service;

    @GetMapping("/list")
    @ApiOperation("Get all ${tableComment}")
    public List&lt;${entityName}&gt; list() {
        return ();
    }

    @PostMapping("/add")
    @ApiOperation("New ${tableComment}")
    public boolean add(@RequestBody ${entityName} entity) {
        return (entity);
    }

    @PutMapping("/update")
    @ApiOperation("renew ${tableComment}")
    public boolean update(@RequestBody ${entityName} entity) {
        return (entity);
    }

    @DeleteMapping("/delete/{id}")
    @ApiOperation("delete ${tableComment}")
    public boolean delete(@PathVariable Long id) {
        return (id);
    }
}

3. Run the generated code

Start the Spring Boot project and configure the database connection.
Run, automatically read table information from the database and generate corresponding code.
View the generated code:
- Entity class: Entity class code that contains database table fields.
- Mapper, Service, ServiceImpl, Controller: Automatically generates interfaces and implementations for adding, deleting, modifying and checking.

4. Test interface

After starting the project, use the Swagger UI to perform interface testing. Visithttp://localhost:8080/You can see the automatically generated interface documents, and directly add, delete, modify and check operations through Swagger's UI.

5. Summary

Through this tutorial, we use Spring Boot, MyBatis-Plus and Velocity template engines to implement an automated code generator, which can automatically generate code for adding, deleting, modifying and searching operations based on the database table structure, and integrates Lombok, Swagger and Knife4j, which greatly improves development efficiency.

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