告别 Spring Boot！Spark Java 极简框架快速开发 RESTful API 全解析

<dependency>
    <groupId>com.sparkjava</groupId>
    <artifactId>spark-core</artifactId>
    <version>2.9.4</version>
</dependency>

import static spark.Spark.*;

public class HelloWorld {
    public static void main(String[] args) {
        // 定义一个 GET 路由
        get("/hello", (req, res) -> "Hello, Spark Java!");
        
        // 可选：设置端口，默认是 4567
        port(8080);
    }
}

# 编译并运行
mvn compile exec:java

# 访问
curl http://localhost:8080/hello
# 响应: Hello, Spark Java!

get("/users", ...);       // 查询
post("/users", ...);      // 创建
put("/users/:id", ...);   // 全量更新
patch("/users/:id", ...); // 部分更新
delete("/users/:id", ...);// 删除

get("/users/:id", (req, res) -> {
    String userId = req.params(":id"); // 获取路径中的 id
    return "User ID: " + userId;
});

get("/search", (req, res) -> {
    String query = req.queryParams("q");
    String page = req.queryParams("page");
    return "Searching for: " + query + " on page " + page;
});

post("/users", (req, res) -> {
    // 假设请求体是 JSON
    User user = new ObjectMapper().readValue(req.body(), User.class);
    // ... 保存用户逻辑
    res.status(201); // 设置状态码为 Created
    return user.getId();
});

before("/api/*", (req, res) -> {
    // 对所有 /api/ 开头的路径进行认证
    String apiKey = req.headers("X-API-Key");
    if (!isValid(apiKey)) {
        halt(401, "Unauthorized"); // 立即终止请求
    }
});

after("/api/*", (req, res) -> {
    // 为所有 API 响应添加统一的头部
    res.header("X-Powered-By", "Spark Java");
    // 统一将响应转换为 JSON
    if (res.body() != null && !res.body().isEmpty()) {
        res.type("application/json");
        res.body(new ObjectMapper().writeValueAsString(res.body()));
    }
});

exception(Exception.class, (exception, request, response) -> {
    log.error("Unhandled exception", exception);
    response.status(500);
    response.body("Internal Server Error");
});

// 处理特定 HTTP 状态码
notFound((request, response) -> {
    response.type("application/json");
    return "{\"error\": \"Resource not found\"}";
});

spark-todo-api/
├── pom.xml
└── src/main/java/
    └── com/example/
        ├── Main.java
        ├── Todo.java
        └── TodoService.java

public class Todo {
    private String id;
    private String title;
    private boolean completed;

    // constructors, getters, setters...
}

public class TodoService {
    private final Map<String, Todo> todos = new ConcurrentHashMap<>();
    private final AtomicInteger counter = new AtomicInteger();

    public List<Todo> getAll() {
        return new ArrayList<>(todos.values());
    }

    public Todo create(Todo todo) {
        String id = String.valueOf(counter.incrementAndGet());
        todo.setId(id);
        todos.put(id, todo);
        return todo;
    }

    public Todo update(String id, Todo updated) {
        if (todos.containsKey(id)) {
            updated.setId(id);
            todos.put(id, updated);
            return updated;
        }
        return null;
    }

    public boolean delete(String id) {
        return todos.remove(id) != null;
    }
}

import static spark.Spark.*;
import com.fasterxml.jackson.databind.ObjectMapper;

public class Main {
    private static final ObjectMapper mapper = new ObjectMapper();
    private static final TodoService service = new TodoService();

    public static void main(String[] args) {
        port(4567);
        // 全局 JSON 响应
        after((req, res) -> {
            if (res.body() != null) {
                res.type("application/json");
                res.body(mapper.writeValueAsString(res.body()));
            }
        });

        // CORS 支持
        options("/*", (request, response) -> {
            String accessControlRequestHeaders = request.headers("Access-Control-Request-Headers");
            if (accessControlRequestHeaders != null) {
                response.header("Access-Control-Allow-Headers", accessControlRequestHeaders);
            }
            String accessControlRequestMethod = request.headers("Access-Control-Request-Method");
            if (accessControlRequestMethod != null) {
                response.header("Access-Control-Allow-Methods", accessControlRequestMethod);
            }
            return "OK";
        });

        before((request, response) -> response.header("Access-Control-Allow-Origin", "*"));

        // API 路由
        get("/todos", (req, res) -> service.getAll());

        post("/todos", (req, res) -> {
            Todo todo = mapper.readValue(req.body(), Todo.class);
            Todo created = service.create(todo);
            res.status(201);
            return created;
        });

        put("/todos/:id", (req, res) -> {
            String id = req.params(":id");
            Todo updated = mapper.readValue(req.body(), Todo.class);
            Todo result = service.update(id, updated);
            if (result == null) {
                res.status(404);
                return "Not Found";
            }
            return result;
        });

        delete("/todos/:id", (req, res) -> {
            String id = req.params(":id");
            boolean deleted = service.delete(id);
            if (!deleted) {
                res.status(404);
                return "Not Found";
            }
            return "";
        });
    }
}

get("/slow-operation", (req, res) -> {
    res.raw().setChunked(true); // 启用分块传输
    CompletableFuture.supplyAsync(() -> {
        // 模拟耗时操作
        Thread.sleep(5000);
        return "Done!";
    }).thenAccept(result -> {
        try {
            res.raw().getWriter().write(result);
            res.raw().getWriter().close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    });
    return ""; // 立即返回，不阻塞
});

// 将 /public 目录下的文件映射到根路径
staticFiles.location("/public");
// 或者指定外部目录
staticFiles.externalLocation("/var/www");

@Test
public void testGetAllTodos() {
    // 启动 Spark 在随机端口
    SparkTest.test(spark -> {
        // ... 定义你的路由
    }, (server) -> {
        // 使用给定的 server 实例进行 HTTP 调用
        HttpResponse response = Unirest.get("http://localhost:" + server.port() + "/todos").asString();
        assertEquals(200, response.getStatus());
    });
}