业务代码存在大量的增删改查功能，只是针对不同的表数据而已。这时候就如果能生成固定的模板代码，那么将大大的解放生产力。本文我们将使用Freemarker模板来生成业务模板代码。

FreeMarker

FreeMarker是一款模板引擎： 即一种基于模板和要改变的数据， 并用来生成输出文本（HTML网页、电子邮件、配置文件、源代码等）的通用工具。其用法原理类似String的replace方法，或MessageFormat的format方法，都是在一定的代码中改变（替换）某些内容。不过FreeMarker更加强大，模板来源可以是外部文件或字符串格式，替换的数据格式多样，而且支持逻辑判断，如此替换的内容将更加灵活。

上代码

准备模板

controller.java.ftl

package ${basePath}.${module}.controller;

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import ${basePath}.common.mybatis.page.BasePage;
import ${basePath}.common.mybatis.page.PageResult;
import ${basePath}.${module}.entity.${classNameUpper};
import ${basePath}.${module}.service.I${classNameUpper}Service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.bind.annotation.*;

/**
 * ${desc}控制器
 *
 * @author lieber
 */
@RestController
@RequestMapping("${router}")
public class ${classNameUpper}Controller {

    private final I${classNameUpper}Service ${classNameLower}Service;

    @Autowired
    public ${classNameUpper}Controller(I${classNameUpper}Service ${classNameLower}Service) {
        this.${classNameLower}Service = ${classNameLower}Service;
    }

    @PostMapping
    public ${classNameUpper} add(@Validated ${classNameUpper} ${classNameLower}) {
        this.${classNameLower}Service.save(${classNameLower});
        return ${classNameLower};
    }

    @DeleteMapping
    public void del(Long id) {
        this.${classNameLower}Service.delete(id);
    }

    @PutMapping
    public ${classNameUpper} edit(@Validated ${classNameUpper} ${classNameLower}) {
        this.${classNameLower}Service.update(${classNameLower});
        return ${classNameLower};
    }

    @GetMapping
    public PageResult<${classNameUpper}> page(BasePage<${classNameUpper}> page) {
    Page<${classNameUpper}> pageRes = this.${classNameLower}Service.page(page);
        return new PageResult<>(pageRes);
    }

    @GetMapping("{id}")
    public ${classNameUpper} detail(@PathVariable Long id) {
        return this.${classNameLower}Service.getById(id);
    }
}

entity.java.ftl

package ${basePath}.${module}.entity;

import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableName;
import ${basePath}.common.mybatis.model.BaseEntity;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.ToString;

import java.io.Serializable;

/**
 * ${desc}
 *
 * @author lieber
 */
@EqualsAndHashCode(callSuper = true)
@ToString(callSuper = true)
@Data
@TableName("t_skp_${tableName}")
public class ${classNameUpper} extends BaseEntity implements Serializable {


}

mapper.java.ftl

package ${basePath}.${module}.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import ${basePath}.${module}.entity.${classNameUpper};
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

/**
 * @author lieber
 */
@Repository
@Mapper
public interface ${classNameUpper}Dao extends BaseMapper<${classNameUpper}> {
}

service.java.ftl

package ${basePath}.${module}.service;

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import ${basePath}.common.mybatis.page.BasePage;
import ${basePath}.${module}.entity.${classNameUpper};

/**
 * @author lieber
 */
public interface I${classNameUpper}Service {
    /**
     * 保存
     *
     * @param ${classNameLower} 对象
     */
    void save(${classNameUpper} ${classNameLower});

    /**
     * 删除
     *
     * @param id id
     */
    void delete(Long id);

    /**
     * 修改
     *
     * @param ${classNameLower} 对象
     */
    void update(${classNameUpper} ${classNameLower});

    /**
     * 分页
     *
     * @param page     分页信息
     * @return 结果
     */
    Page<${classNameUpper}> page(BasePage<${classNameUpper}> page);

    /**
    * 通过id获取
    *
    * @param id id
    * @return 详情
    */
    ${classNameUpper} getById(Long id);
}

serviceImpl.java.ftl

package ${basePath}.${module}.service.impl;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import ${basePath}.common.mybatis.page.BasePage;
import ${basePath}.${module}.dao.${classNameUpper}Dao;
import ${basePath}.${module}.entity.${classNameUpper};
import ${basePath}.${module}.service.I${classNameUpper}Service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.Objects;

/**
 * @author lieber
 */
@Service
public class ${classNameUpper}ServiceImpl implements I${classNameUpper}Service {

    private final ${classNameUpper}Dao ${classNameLower}Dao;

    @Autowired
    public ${classNameUpper}ServiceImpl(${classNameUpper}Dao ${classNameLower}Dao) {
        this.${classNameLower}Dao = ${classNameLower}Dao;
    }

    @Override
    public void save(${classNameUpper} ${classNameLower}) {
        ${classNameLower}.set(false);
        this.${classNameLower}Dao.insert(${classNameLower});
    }

    @Override
    public void delete(Long id) {
        this.${classNameLower}Dao.deleteById(id);
    }

    @Override
    public void update(${classNameUpper} ${classNameLower}) {
        ${classNameLower}.set(true);
        this.${classNameLower}Dao.updateById(${classNameLower});
    }

    @Override
    public Page<${classNameUpper}> page(BasePage<${classNameUpper}> page) {
    QueryWrapper<${classNameUpper}> queryWrapper = new QueryWrapper<>();
        return this.${classNameLower}Dao.selectPage(page.toPage(), queryWrapper);
    }

    @Override
    public ${classNameUpper} getById(Long id) {
        if (Objects.isNull(id) || id < 0) {
            return null;
        }
        return this.${classNameLower}Dao.selectById(id);
    }
}

引入freemarker处理包

此处仅引入freemarker，其余相关包在父级

<dependency>
            <groupId>org.freemarker</groupId>
            <artifactId>freemarker</artifactId>
</dependency>

编码替换

原理很简单，在此不过多赘述，直接上代码
CodeGenerator

package com.yugioh.code;

import com.sun.javafx.PlatformUtil;
import freemarker.template.Configuration;
import freemarker.template.Template;
import freemarker.template.TemplateException;

import java.io.*;
import java.util.*;

/**
 * @author lieber
 */
public class CodeGenerator {


    public static void main(String[] args) throws IOException, TemplateException {
        CodeModel codeModel = new CodeModel();
        codeModel.setRouter("test");
        codeModel.setClassNameLower("test");
        codeModel.setClassNameUpper("Test");
        codeModel.setModule("ready");
        codeModel.setTableName("test");
        codeModel.setDesc("test");
        gen(codeModel);
    }

    public static void gen(CodeModel codeModel) throws IOException, TemplateException {
        for (Type type : Type.values()) {
            genFile(codeModel, type);
        }
    }

    private static void genFile(CodeModel codeModel, Type type) throws IOException, TemplateException {
        FileOutputStream stream = null;
        OutputStreamWriter outputStreamWriter = null;
        try {
            Map<String, Object> rootMap = getGenMap(codeModel);
            String projectPath = System.getProperty("user.dir");
            Configuration configuration = new Configuration(Configuration.getVersion());
            String templatePath = projectPath + "/code-gen/src/main/resources/templates/";

            configuration.setDirectoryForTemplateLoading(new File(parsePath(templatePath)));
            Template template = configuration.getTemplate(type.getPath());

            String savePath = projectPath + "/" + codeModel.getModule() + "/src/main/java/" + codeModel.getBasePath().replaceAll("\\.", "/") + "/" + codeModel.getModule() + "/" + type.getPackageName();

            File dir = new File(parsePath(savePath));
            if (!dir.exists()) {
                if (!dir.mkdirs()) {
                    throw new IOException("创建文件夹失败");
                }
            }
            stream = new FileOutputStream(parsePath(savePath + "/" + String.format(type.getClassName(), codeModel.getClassNameUpper())));
            outputStreamWriter = new OutputStreamWriter(stream);
            template.process(rootMap, outputStreamWriter);
            outputStreamWriter.flush();
            outputStreamWriter.close();
            stream.close();
        } finally {
            if (outputStreamWriter != null) {
                outputStreamWriter.close();
            }
            if (stream != null) {
                stream.close();
            }
        }
    }

    private static Map<String, Object> getGenMap(CodeModel codeModel) {
        Map<String, Object> genMap = new HashMap<>(16);
        genMap.put("basePath", codeModel.getBasePath());
        genMap.put("router", codeModel.getRouter());
        genMap.put("desc", codeModel.getDesc());
        genMap.put("classNameUpper", codeModel.getClassNameUpper());
        genMap.put("classNameLower", codeModel.getClassNameLower());
        genMap.put("module", codeModel.getModule());
        genMap.put("tableName", codeModel.getTableName());
        return genMap;
    }

    private static String parsePath(String path) {
        if (PlatformUtil.isWindows()) {
            return path.replaceAll("/+|\\\\+", "\\\\");
        } else {
            return path.replaceAll("/+|\\\\+", "/");
        }
    }

    public enum Type {
        /**
         * 控制器
         */
        CONTROLLER("controller.java.ftl", "controller", "%sController.java"),
        /**
         * 实体
         */
        ENTITY("entity.java.ftl", "entity", "%s.java"),
        /**
         * 数据库mapper
         */
        MAPPER("mapper.java.ftl", "dao", "%sDao.java"),
        /**
         * service接口
         */
        SERVICE("service.java.ftl", "service", "I%sService.java"),
        /**
         * service实现
         */
        SERVICE_IMPL("serviceImpl.java.ftl", "service/impl", "%sServiceImpl.java");

        private String path;
        private String packageName;
        private String className;

        Type(String path, String packageName, String className) {
            this.path = path;
            this.packageName = packageName;
            this.className = className;
        }

        public String getPath() {
            return path;
        }

        public String getPackageName() {
            return packageName;
        }

        public String getClassName() {
            return className;
        }
    }
}

CodeModel

package com.yugioh.code;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

/**
 * @author lieber
 */
@Data
@AllArgsConstructor
@NoArgsConstructor
public class CodeModel {

    private String basePath = "com.yugioh";

    private String router;

    private String desc;

    private String classNameUpper;

    private String classNameLower;

    private String module;

    private String tableName;
}

其它

这里只是简单的创建了模板，还可以扩展到自动从数据库拉取字段创建实体等。