在后端开发中，我们经常需要根据业务数据动态生成各种文本内容：从配置文件到源代码，从SQL脚本到部署文档。
这些重复性的生成任务不仅耗时耗力，还容易出错。模板引擎为我们提供了一种有效的解决方案。
后端开发的重复性工作痛点
在后端开发过程中，经常存在大量重复性的工作需要完成
1. 配置文件需要根据环境动态生成
- 多环境配置管理：需要根据数据库类型、环境参数等信息生成不同的application.yml配置文件
- 基础设施配置：Nginx、Docker、Kubernetes等配置文件需要根据服务信息动态生成
- 配置模板复用：不同项目的配置结构相似，但参数不同，需要统一的配置模板
2. 代码结构高度相似需要模板化生成
- CRUD代码生成：根据数据库表结构自动生成Entity、Repository、Service、Controller等代码
- API接口文档生成：基于Controller注解自动生成接口文档，保持文档与代码同步
- 项目脚手架：创建新项目时快速生成标准化的基础代码结构
3. 文档和脚本需要标准化模板
- 数据库设计文档：根据表结构信息自动生成数据库设计文档
- 部署脚本生成：根据项目配置自动生成部署脚本和说明文档
- API文档同步：基于代码中的注解和结构生成最新的API文档
4. 通知和报表需要动态内容生成
- 邮件内容模板化：用户注册、密码重置、订单通知等邮件内容需要根据用户数据动态生成
- 日志格式标准化：统一的日志格式模板，包含时间戳、请求ID、用户信息等字段
解决方案：基于模板引擎的自动化生成
模板引擎通过将模板与数据分离，实现了文本内容的自动化生成。核心思想是：
- 模板定义：创建包含占位符和控制逻辑的模板文件
- 数据准备：构建包含生成所需数据的数据模型
- 引擎处理：模板引擎将数据与模板结合，生成最终的文本内容
工作原理详解
模板引擎的工作流程可以分为以下几个步骤：
- 1. 模板解析：引擎解析模板文件，构建抽象语法树（AST）
- 2. 数据绑定：将传入的数据对象与模板中的变量进行绑定
- 3. 表达式求值：计算模板中的表达式，生成动态内容
- 4. 内容生成：将处理后的内容输出为目标格式
技术选型
在后端场景中，常用的模板引擎有FreeMarker、Velocity和Thymeleaf等。
Spring Boot集成FreeMarker：
xml
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-freemarker</artifactId> </dependency>
基础配置示例：
yaml
spring: freemarker: template-loader-path: classpath:/templates/ suffix: .ftl charset: UTF-8 content-type: text/plain cache: true # 生产环境建议开启缓存 settings: template_update_delay_milliseconds: 0 default_encoding: UTF-8 output_encoding: UTF-8 locale: zh_CN datetime_format: yyyy-MM-dd HH:mm:ss number_format: 0.## boolean_format: true,false
模板引擎的优势
相比传统的字符串拼接或硬编码方式，模板引擎具有明显优势：
- 1. 可维护性强：模板文件与业务代码分离，修改模板不需要重新编译
- 2. 可读性好：模板语法接近自然语言，易于理解和维护
- 3. 功能丰富：内置条件判断、循环、函数调用等强大功能
- 4. 缓存机制：支持模板缓存，提高生成性能
- 5. 错误处理：提供详细的错误信息，便于调试和问题定位
配置文件生成实战
1. Nginx配置生成器
模板文件 templates/config/nginx.conf.ftl
nginx
# Nginx Configuration for ${serviceName} # Generated at: .now upstream ${serviceName}_backend { #least_conn; <#list servers as server> server ${server.host}:${server.port}<#if server.weight??> weight=${server.weight}</#if>; </#list> } server { listen ${port}; server_name ${domain}; access_log /var/log/nginx/${serviceName}_access.log; error_log /var/log/nginx/${serviceName}_error.log; <#if sslEnabled> ssl_certificate ${sslCertificatePath}; ssl_certificate_key ${sslCertificateKeyPath}; ssl_protocols TLSv1.2 TLSv1.3; ssl_ciphers HIGH:!aNULL:!MD5; </#if> location / { proxy_pass http://${serviceName}_backend; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header X-Forwarded-Proto $scheme; <#if timeout??> proxy_connect_timeout ${timeout}; proxy_send_timeout ${timeout}; proxy_read_timeout ${timeout}; </#if> } <#if staticPath??> location /static/ { alias ${staticPath}/; expires 1d; add_header Cache-Control "public, immutable"; } </#if> <#if healthCheckPath??> location ${healthCheckPath} { access_log off; return 200 "healthy\n"; add_header Content-Type text/plain; } </#if> }
配置生成服务
java
@Service public class ConfigGeneratorService { @Autowired private Configuration freemarkerConfig; public String generateNginxConfig(NginxConfig config) throws IOException, TemplateException { Template template = freemarkerConfig.getTemplate("config/nginx.conf.ftl"); // 添加当前时间戳 config.setNow(LocalDateTime.now().format(DateTimeFormatter.ISO_LOCAL_DATE_TIME)); try(StringWriter out = new StringWriter()) { template.process(config, out); return out.toString(); } } public void saveConfigToFile(String configContent, String outputPath) throws IOException { Path path = Paths.get(outputPath); Files.createDirectories(path.getParent()); Files.write(path, configContent.getBytes(StandardCharsets.UTF_8)); } } // 配置数据模型 @Data public class NginxConfig { private String serviceName; private String domain; private int port; private boolean sslEnabled; private String sslCertificatePath; private String sslCertificateKeyPath; private String staticPath; private String healthCheckPath; private Integer timeout; private List<ServerInfo> servers = new ArrayList<>(); @Data public static class ServerInfo { private String host; private int port; private Integer weight; } }
使用示例
java
@RestController @RequestMapping("/api/config") public class ConfigController { @Autowired private ConfigGeneratorService configGenerator; @PostMapping("/nginx") public ResponseEntity<String> generateNginxConfig(@RequestBody NginxConfig config) { try { String configContent = configGenerator.generateNginxConfig(config); // 保存到文件 String outputPath = "/etc/nginx/sites-available/" + config.getServiceName() + ".conf"; configGenerator.saveConfigToFile(configContent, outputPath); return ResponseEntity.ok(configContent); } catch (Exception e) { return ResponseEntity.status(500).body("配置生成失败: " + e.getMessage()); } } }
2. Docker Compose配置生成
模板文件 templates/config/docker-compose.yml.ft
version: '3.8' services: <#list services as service> ${service.name}: image: ${service.image}:${service.tag} container_name: ${service.containerName} <#if service.ports??> ports: <#list service.ports as port> - "${port.host}:${port.container}" </#list> </#if> <#if service.environment??> environment: <#list service.environment as key, value> ${key}: "${value}" </#list> </#if> <#if service.volumes??> volumes: <#list service.volumes as volume> - ${volume.host}:${volume.container} </#list> </#if> <#if service.dependsOn??> depends_on: <#list service.dependsOn as dependency> - ${dependency} </#list> </#if> <#if service.networks??> networks: <#list service.networks as network> - ${network} </#list> </#if> restart: unless-stopped </#list> <#if networks??> networks: <#list networks as network> ${network.name}: driver: ${network.driver!"bridge"} </#list> </#if> <#if volumes??> volumes: <#list volumes as volume> ${volume.name}: </#list> </#if>
代码生成实战
1. CRUD代码生成器
实体类模板 templates/code/Entity.java.ftl
java
package ${packageName}.entity; <#list imports as import> import ${import}; </#list> /** * ${tableName} 实体类 * * @author ${author} * @since ${date} */ @Data <#if tableName??> @TableName("${tableName}") </#if> public class ${className} implements Serializable { private static final long serialVersionUID = 1L; <#list fields as field> /** ${field.comment!} */ <#if field.id> @TableId(type = IdType.${field.idType!"AUTO"}) </#if> <#if field.notNull> @NotNull(message = "${field.comment!}不能为空") </#if> <#if field.length??> @Size(max = ${field.length}, message = "${field.comment!}长度不能超过${field.length}") </#if> private ${field.type} ${field.name}; </#list> <#-- Getter和Setter方法由Lombok @Data注解自动生成 --> }
Service接口模板 templates/code/Service.java.ftl
java
package ${packageName}.service; import ${packageName}.entity.${className}; import com.baomidou.mybatisplus.extension.plugins.pagination.Page; import java.util.List; /** * ${className} 服务接口 * * @author ${author} * @since ${date} */ public interface ${className}Service { /** * 分页查询${className} */ Page<${className}> select${className}Page(int page, int size, ${className} ${classNameInstance}); /** * 根据ID查询${className} */ ${className} select${className}ById(${primaryKey.type} ${primaryKey.name}); /** * 新增${className} */ int insert${className}(${className} ${classNameInstance}); /** * 修改${className} */ int update${className}(${className} ${classNameInstance}); /** * 批量删除${className} */ int delete${className}ByIds(List<${primaryKey.type}> ids); /** * 删除${className} */ int delete${className}ById(${primaryKey.type} ${primaryKey.name}); }
Controller模板 templates/code/Controller.java.ftl
java
package ${packageName}.controller; import ${packageName}.entity.${className}; import ${packageName}.service.${className}Service; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.*; import io.swagger.annotations.Api; import io.swagger.annotations.ApiOperation; import com.baomidou.mybatisplus.extension.plugins.pagination.Page; /** * ${className} 控制器 * * @author ${author} * @since ${date} */ @Api(tags = "${className}管理") @RestController @RequestMapping("/api/${classNameInstance}") public class ${className}Controller { @Autowired private ${className}Service ${classNameInstance}Service; @ApiOperation("分页查询${className}") @GetMapping("/page") public Page<${className}> get${className}Page( @RequestParam(defaultValue = "1") int page, @RequestParam(defaultValue = "10") int size, ${className} ${classNameInstance}) { return ${classNameInstance}Service.select${className}Page(page, size, ${classNameInstance}); } @ApiOperation("根据ID查询${className}") @GetMapping("/{id}") public ${className} get${className}ById(@PathVariable ${primaryKey.type} id) { return ${classNameInstance}Service.select${className}ById(id); } @ApiOperation("新增${className}") @PostMapping public int create${className}(@RequestBody ${className} ${classNameInstance}) { return ${classNameInstance}Service.insert${className}(${classNameInstance}); } @ApiOperation("修改${className}") @PutMapping("/{id}") public int update${className}(@PathVariable ${primaryKey.type} id, @RequestBody ${className} ${classNameInstance}) { ${classNameInstance}.set${primaryKey.name?cap_first}(id); return ${classNameInstance}Service.update${className}(${classNameInstance}); } @ApiOperation("删除${className}") @DeleteMapping("/{id}") public int delete${className}(@PathVariable ${primaryKey.type} id) { return ${classNameInstance}Service.delete${className}ById(id); } }
代码生成服务
java
@Service public class CodeGeneratorService { @Autowired private Configuration freemarkerConfig; @Value("${code.output.path}") private String outputBasePath; public void generateCode(GenerateRequest request) throws Exception { Map<String, Object> dataModel = buildDataModel(request); // 生成实体类 generateFile("code/Entity.java.ftl", getEntityPath(request.getPackageName(), request.getClassName()), dataModel); // 生成Service接口 generateFile("code/Service.java.ftl", getServicePath(request.getPackageName(), request.getClassName()), dataModel); // 生成Controller generateFile("code/Controller.java.ftl", getControllerPath(request.getPackageName(), request.getClassName()), dataModel); } private Map<String, Object> buildDataModel(GenerateRequest request) { Map<String, Object> dataModel = new HashMap<>(); dataModel.put("packageName", request.getPackageName()); dataModel.put("className", request.getClassName()); dataModel.put("classNameInstance", StringUtils.uncapitalize(request.getClassName())); dataModel.put("tableName", request.getTableName()); dataModel.put("author", request.getAuthor()); dataModel.put("date", LocalDate.now().toString()); dataModel.put("fields", request.getFields()); dataModel.put("primaryKey", findPrimaryKey(request.getFields())); dataModel.put("imports", calculateImports(request.getFields())); return dataModel; } private void generateFile(String templateName, String outputPath, Map<String, Object> dataModel) throws IOException, TemplateException { Template template = freemarkerConfig.getTemplate(templateName); Path path = Paths.get(outputBasePath, outputPath); Files.createDirectories(path.getParent()); try(StringWriter out = new StringWriter()) { template.process(dataModel, out); Files.write(path, out.toString().getBytes(StandardCharsets.UTF_8)); } } // 工具方法 private String getEntityPath(String packageName, String className) { return packageName.replace('.', '/') + "/entity/" + className + ".java"; } private String getServicePath(String packageName, String className) { return packageName.replace('.', '/') + "/service/" + className + "Service.java"; } private String getControllerPath(String packageName, String className) { return packageName.replace('.', '/') + "/controller/" + className + "Controller.java"; } }
邮件模板处理
1. HTML邮件模板
模板文件 templates/email/welcome.html.ftl
html
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title>欢迎加入${companyName}</title> <style> body { font-family: Arial, sans-serif; line-height: 1.6; color: #333; } .container { max-width: 600px; margin: 0 auto; padding: 20px; } .header { background-color: #007bff; color: white; padding: 20px; text-align: center; } .content { padding: 20px; } .footer { background-color: #f8f9fa; padding: 10px; text-align: center; font-size: 12px; } .button { display: inline-block; padding: 12px 24px; background-color: #28a745; color: white; text-decoration: none; border-radius: 4px; margin: 20px 0; } </style> </head> <body> <div class="container"> <div class="header"> <h1>欢迎加入${companyName}！</h1> </div> <div class="content"> <h2>亲爱的${user.name}，</h2> <p>感谢您注册${companyName}！您的账户已经创建成功。</p> <p>您的账户信息：</p> <ul> <li>用户名：${user.username}</li> <li>邮箱：${user.email}</li> <#if user.phone??> <li>手机号：${user.phone}</li> </#if> </ul> <p>请点击下面的按钮激活您的账户：</p> <div style="text-align: center;"> <a href="${activationUrl}" class="button">激活账户</a> </div> <#if activationToken??> <p>如果按钮无法点击，请复制以下链接到浏览器：</p> <p style="word-break: break-all; background-color: #f8f9fa; padding: 10px;"> ${activationUrl}?token=${activationToken} </p> </#if> <p>激活链接将在${expiryHours}小时后失效，请尽快完成激活。</p> </div> <div class="footer"> <p>此邮件由系统自动发送，请勿回复。</p> <p>© ${currentYear} ${companyName}. 保留所有权利。</p> <#if unsubscribeUrl??> <p><a href="${unsubscribeUrl}">取消订阅</a></p> </#if> </div> </div> </body> </html>
邮件服务
java
@Service public class EmailService { @Autowired private Configuration freemarkerConfig; @Autowired private JavaMailSender mailSender; @Value("${spring.mail.from}") private String fromEmail; public void sendWelcomeEmail(User user, String activationToken) throws Exception { Map<String, Object> dataModel = new HashMap<>(); dataModel.put("user", user); dataModel.put("companyName", "我的公司"); dataModel.put("activationUrl", "https://myapp.com/activate"); dataModel.put("activationToken", activationToken); dataModel.put("expiryHours", 24); dataModel.put("currentYear", Year.now().getValue()); Template template = freemarkerConfig.getTemplate("email/welcome.html.ftl"); try(StringWriter out = new StringWriter()) { template.process(dataModel, out); MimeMessage message = mailSender.createMimeMessage(); MimeMessageHelper helper = new MimeMessageHelper(message, true, "UTF-8"); helper.setFrom(fromEmail); helper.setTo(user.getEmail()); helper.setSubject("欢迎加入" + dataModel.get("companyName")); helper.setText(out.toString(), true); // true表示HTML格式 mailSender.send(message); } } }
高级技巧与最佳实践
1. 模板继承与片段复用
基础配置模板 templates/config/base.conf.ftl
conf
# 基础配置文件 # 生成时间: ${generationTime} # 环境: ${environment} <#macro logConfig> # 日志配置 logging.level.root=${logLevel!"INFO"} logging.pattern.console=%d{yyyy-MM-dd HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n </#macro> <#macro databaseConfig> # 数据库配置 spring.datasource.url=${database.url} spring.datasource.username=${database.username} spring.datasource.password=${database.password} spring.datasource.driver-class-name=${database.driver!"com.mysql.cj.jdbc.Driver"} </#macro> <#macro serverConfig> # 服务器配置 server.port=${server.port!8080} server.servlet.context-path=${server.contextPath!"/"} </#macro>
具体配置模板 templates/config/application.yml.ftl
yaml
<#include "base.conf.ftl"> # Spring Boot Application Configuration <@serverConfig/> <@databaseConfig/> <@logConfig/> # 应用特定配置 app: name: ${appName} version: ${appVersion!"1.0.0"} <#if customConfig??> <#list customConfig as key, value> ${key}: ${value} </#list> </#if> <#if profiles??> spring: profiles: active: ${profiles.active!"dev"} </#if>
2. 模板缓存与性能优化
java
@Configuration public class TemplateConfig { @Bean public Configuration freemarkerConfig() throws TemplateModelException { Configuration config = new Configuration(Configuration.VERSION_2_3_31); config.setClassForTemplateLoading(this.getClass(), "/templates"); // 编码设置 config.setDefaultEncoding("UTF-8"); // 数字格式化 config.setNumberFormat("0.######"); // 缓存设置 config.setTemplateUpdateDelayMilliseconds(30000); // 30秒检查一次模板更新 config.setCacheStorage(new freemarker.cache.MruCacheStorage(100, 250)); // 错误处理 config.setTemplateExceptionHandler(TemplateExceptionHandler.RETHROW_HANDLER); // 自定义指令 config.setSharedVariable("formatDate", new DateFormatMethod()); config.setSharedVariable("toJson", new ToJsonMethod()); return config; } // 自定义日期格式化方法 public static class DateFormatMethod implements TemplateMethodModelEx { @Override public Object exec(List arguments) throws TemplateModelException { if (arguments.size() != 2) { throw new TemplateModelException("需要两个参数：日期和格式"); } Object dateObj = arguments.get(0); Object formatObj = arguments.get(1); if (dateObj instanceof Date && formatObj instanceof SimpleScalar) { Date date = (Date) dateObj; String format = ((SimpleScalar) formatObj).getAsString(); SimpleDateFormat sdf = new SimpleDateFormat(format); return sdf.format(date); } return dateObj.toString(); } } // JSON转换方法 public static class ToJsonMethod implements TemplateMethodModelEx { private final ObjectMapper objectMapper = new ObjectMapper(); @Override public Object exec(List arguments) throws TemplateModelException { if (arguments.size() != 1) { throw new TemplateModelException("需要一个参数：要转换的对象"); } try { return objectMapper.writeValueAsString(arguments.get(0)); } catch (Exception e) { throw new TemplateModelException("JSON转换失败: " + e.getMessage()); } } } }
3. 模板安全管理
java
@Component public class TemplateSecurityManager { public Configuration createSecureConfig() throws TemplateModelException { Configuration config = new Configuration(Configuration.VERSION_2_3_31); // 限制模板中的Java对象访问 config.setNewBuiltinClassResolver(TemplateClassResolver.SAFER_RESOLVER); // 禁用危险的方法调用 config.setSetting("freemarker.template.utility.Execute", "disabled"); config.setSetting("freemarker.template.utility.ObjectConstructor", "disabled"); // 限制可访问的包 config.setSetting("freemarker.ext.beans.BeansWrapper", "restricted"); return config; } public boolean validateTemplate(String templateContent) { // 检查模板中是否包含危险代码 String[] dangerousPatterns = { "new\\s*java\\.io", "System\\.exit", "Runtime\\.getRuntime", "ProcessBuilder", "Class\\.forName", "Method\\.invoke" }; for (String pattern : dangerousPatterns) { if (Pattern.compile(pattern).matcher(templateContent).find()) { return false; } } return true; } }
总结
Spring Boot模板引擎为后端开发提供了强大的自动化生成能力，有效解决了重复性工作的痛点，通过掌握Spring Boot模板引擎，开发者能够构建高效的自动化工具链，将更多精力投入到业务逻辑的实现中，提升整体开发效率和代码质量。
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