Spring Boot 3中使用JTE预编译模板抛出ClassNotFoundException问题求助

在Spring Boot 3.2中使用JTE生成非HTML文件，未采用jte-spring-boot-starter-3。本地测试时配置正常，但Docker容器运行应用时抛出ClassNotFoundException。打包后的JAR结构中存在gg.jte.generated.precompiled目录，但调用生成方法时仍报错。

Maven插件配置 #

<plugin>
    <groupId>gg.jte</groupId>
    <artifactId>jte-maven-plugin</artifactId>
    <version>${jte.version}</version>
    <configuration>
        <sourceDirectory>${project.basedir}/src/main/jte</sourceDirectory>
        <targetDirectory>${project.build.directory}/jte-classes</targetDirectory>
        <contentType>Plain</contentType>
    </configuration>
    <executions>
        <execution>
            <phase>generate-sources</phase>
            <goals>
                <goal>generate</goal>
            </goals>
        </execution>
    </executions>
</plugin>

TemplateEngine使用代码 #

@Service
public class GenerateUseCase {
    private final TemplateEngine jteTemplateEngine;

    public GenerateUseCase() throws IOException {
        this.jteTemplateEngine = TemplateEngine.createPrecompiled(ContentType.Plain);
    }

    private void generateFileByTemplate(final Path dir, final Map<String, Object> params,
                                        final String fileName) throws IOException {

        final File file = dir.resolve(fileName).toFile();

        file.createNewFile();

        try (FileOutput output = new FileOutput(file.getAbsoluteFile().toPath(), StandardCharsets.UTF_8)) {
            jteTemplateEngine.render(fileName + ".jte", params, output);
        }
    }
}

报错堆栈 #

Servlet.service() for servlet [dispatcherServlet] in context with path [/] threw exception [Request processing failed: java.lang.RuntimeException: gg.jte.TemplateNotFoundException: Failed to load ingress.yml.jte] with root cause

java.lang.ClassNotFoundException: gg.jte.generated.precompiled.JteingressymlGenerated
    at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:445)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:593)
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
    at gg.jte.runtime.TemplateLoader.load(TemplateLoader.java:25)
    at java.base/java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1708)
    at gg.jte.TemplateEngine.resolveTemplate(TemplateEngine.java:339)
    at gg.jte.TemplateEngine.render(TemplateEngine.java:228)
    at org.service.GenerateUseCase.generateFileByTemplate(GenerateUseCase.java:151)

1. 确保预编译JTE类被打包进JAR #

当前JTE插件将生成的类输出到target/jte-classes，但Spring Boot Maven插件默认不会把该目录下的类打包进最终JAR，可通过以下三种方式解决：

方案A：调整JTE插件输出目录到源码目录 #

修改jte-maven-plugin的targetDirectory为src/main/java（建议将生成的类添加到.gitignore，避免提交）：

<configuration>
    <sourceDirectory>${project.basedir}/src/main/jte</sourceDirectory>
    <targetDirectory>${project.basedir}/src/main/java</targetDirectory>
    <contentType>Plain</contentType>
</configuration>

方案B：配置Spring Boot插件包含jte-classes目录 #

在spring-boot-maven-plugin中添加配置，将jte-classes作为额外类目录：

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <additionalClasspathElements>
            <additionalClasspathElement>${project.build.directory}/jte-classes</additionalClasspathElement>
        </additionalClasspathElements>
    </configuration>
</plugin>

方案C：用资源插件复制生成类到classes目录 #

添加maven-resources-plugin，在构建阶段将jte-classes下的类复制到target/classes：

<plugin>
    <artifactId>maven-resources-plugin</artifactId>
    <executions>
        <execution>
            <id>copy-jte-classes</id>
            <phase>process-classes</phase>
            <goals>
                <goal>copy-resources</goal>
            </goals>
            <configuration>
                <outputDirectory>${project.build.directory}/classes</outputDirectory>
                <resources>
                    <resource>
                        <directory>${project.build.directory}/jte-classes</directory>
                        <includes>
                            <include>**/*.class</include>
                        </includes>
                    </resource>
                </resources>
            </configuration>
        </execution>
    </executions>
</plugin>

2. 检查Docker构建流程 #

确保Dockerfile执行完整的Maven构建，包含generate-sources和package阶段，避免直接复制本地JAR：

FROM maven:3.8.6-openjdk-17 AS build
WORKDIR /app
COPY pom.xml .
RUN mvn dependency:go-offline
COPY src ./src
RUN mvn clean package -DskipTests

FROM openjdk:17-jdk-slim
WORKDIR /app
COPY --from=build /app/target/your-app.jar app.jar
ENTRYPOINT ["java", "-jar", "app.jar"]

3. 显式指定类加载器（可选） #

若类加载器存在问题，创建TemplateEngine时传入当前类的类加载器：

public GenerateUseCase() throws IOException {
    this.jteTemplateEngine = TemplateEngine.createPrecompiled(ContentType.Plain, getClass().getClassLoader());
}

内容的提问来源于stack exchange，提问作者Alina Didenko