# Dify指定知识库实现方案

## 🎯 问题分析

**需求**：在调用Dify对话API时，动态指定使用哪些知识库（Dataset）

**场景**：不同部门用户使用同一个智能体，但只能访问各自授权的知识库

---

## 📋 Dify官方支持的方式

### 方式1：知识库检索API + LLM组合（推荐⭐⭐）

**优点**：
- ✅ 完全控制知识库选择
- ✅ 可以实现复杂的权限逻辑
- ✅ 灵活性最高

**缺点**：
- ⚠️ 需要自己组合API调用
- ⚠️ 无法使用Dify的完整对话管理功能

#### 步骤1：检索相关知识

```http
POST https://api.dify.ai/v1/datasets/{dataset_id}/retrieve
Authorization: Bearer {api_key}
Content-Type: application/json

{
  "query": "如何申请奖学金？",
  "top_k": 3,
  "score_threshold": 0.7
}
```

**响应示例：**
```json
{
  "records": [
    {
      "content": "申请奖学金需要满足以下条件...",
      "score": 0.95,
      "metadata": {
        "document_id": "doc-123",
        "document_name": "奖学金管理办法.pdf"
      }
    }
  ]
}
```

#### 步骤2：多知识库并行检索

```java
@Service
public class DifyKnowledgeService {
    
    /**
     * 从多个知识库检索相关内容
     */
    public List<RetrievalRecord> retrieveFromMultipleDatasets(
            String query,
            List<String> datasetIds,
            int topK) {
        
        List<CompletableFuture<List<RetrievalRecord>>> futures = datasetIds.stream()
            .map(datasetId -> CompletableFuture.supplyAsync(() -> 
                retrieveFromDataset(datasetId, query, topK)
            ))
            .collect(Collectors.toList());
        
        // 等待所有检索完成
        CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
        
        // 合并结果并按分数排序
        return futures.stream()
            .map(CompletableFuture::join)
            .flatMap(List::stream)
            .sorted((a, b) -> Double.compare(b.getScore(), a.getScore()))
            .limit(topK)
            .collect(Collectors.toList());
    }
    
    /**
     * 从单个知识库检索
     */
    private List<RetrievalRecord> retrieveFromDataset(
            String datasetId, 
            String query, 
            int topK) {
        
        String url = difyConfig.getFullApiUrl("/datasets/" + datasetId + "/retrieve");
        
        Map<String, Object> requestBody = new HashMap<>();
        requestBody.put("query", query);
        requestBody.put("top_k", topK);
        requestBody.put("score_threshold", 0.7);
        
        // HTTP请求
        HttpResponse response = httpClient.post(url)
            .header("Authorization", "Bearer " + apiKey)
            .body(requestBody)
            .execute();
        
        return parseRetrievalResponse(response);
    }
}
```

#### 步骤3：组合上下文调用LLM

```java
/**
 * 使用检索到的知识回答问题
 */
public String chatWithRetrievedKnowledge(
        String query,
        List<RetrievalRecord> records,
        String conversationId) {
    
    // 构建上下文
    String context = records.stream()
        .map(r -> "【" + r.getMetadata().get("document_name") + "】\n" + r.getContent())
        .collect(Collectors.joining("\n\n"));
    
    // 构建Prompt
    String prompt = String.format(
        "请基于以下知识库内容回答用户问题。如果知识库中没有相关信息，请明确告知用户。\n\n" +
        "知识库内容：\n%s\n\n" +
        "用户问题：%s\n\n" +
        "回答：",
        context, query
    );
    
    // 调用Dify Completion API或直接调用LLM
    return callLLM(prompt, conversationId);
}
```

---

### 方式2：Dify Workflow（工作流）⭐

**原理**：创建工作流，使用变量控制知识库选择

#### Dify工作流配置

```yaml
workflow_nodes:
  - id: start
    type: start
    outputs:
      - query          # 用户问题
      - dataset_ids    # 知识库ID列表（变量）
  
  - id: kb_retrieval
    type: knowledge-retrieval
    inputs:
      query: "{{#start.query#}}"
      datasets: "{{#start.dataset_ids#}}"  # 从输入变量读取
      top_k: 3
    outputs:
      - result
  
  - id: llm
    type: llm
    inputs:
      prompt: |
        基于以下知识库内容回答问题：
        {{#kb_retrieval.result#}}
        
        用户问题：{{#start.query#}}
    outputs:
      - answer
  
  - id: end
    type: end
    outputs:
      - answer: "{{#llm.answer#}}"
```

#### API调用示例

```java
/**
 * 调用Dify Workflow
 */
public void chatWithWorkflow(
        String query,
        List<String> datasetIds,
        String userId,
        SseEmitter emitter) {
    
    String url = difyConfig.getFullApiUrl("/workflows/run");
    
    Map<String, Object> inputs = new HashMap<>();
    inputs.put("query", query);
    inputs.put("dataset_ids", datasetIds);  // ⭐ 动态传入知识库列表
    
    Map<String, Object> requestBody = new HashMap<>();
    requestBody.put("inputs", inputs);
    requestBody.put("response_mode", "streaming");
    requestBody.put("user", userId);
    
    // 流式请求
    httpClient.postStream(url, requestBody, new StreamCallback() {
        @Override
        public void onChunk(String chunk) {
            emitter.send(chunk);
        }
    });
}
```

**HTTP请求示例：**
```http
POST /v1/workflows/run
Authorization: Bearer {api_key}
Content-Type: application/json

{
  "inputs": {
    "query": "如何申请奖学金？",
    "dataset_ids": ["dataset-edu-001", "dataset-public-001"]
  },
  "response_mode": "streaming",
  "user": "user-123"
}
```

---

### 方式3：多应用切换（不推荐）

为不同部门创建不同的Dify应用：

```
部门A -> App A（绑定知识库A1, A2）
部门B -> App B（绑定知识库B1, B2）
```

**缺点**：
- ❌ 管理复杂
- ❌ 无法共享公共知识库
- ❌ 扩展性差

---

## 🎨 推荐实现方案

### 方案：知识库检索API + 自定义LLM调用

#### 完整实现代码

```java
@Service
public class AiChatServiceImpl implements AiChatService {
    
    @Autowired
    private AiKnowledgeMapper knowledgeMapper;
    
    @Autowired
    private DifyApiClient difyApiClient;
    
    @Autowired
    private AiMessageMapper messageMapper;
    
    /**
     * 流式对话（带知识库权限隔离）
     */
    @Override
    public void streamChat(
            String message,
            String conversationId,
            String userId,
            SseEmitter emitter) {
        
        try {
            // 1. 获取当前登录用户的部门角色信息（通过LoginUtil）⭐
            List<UserDeptRoleVO> userDeptRoles = LoginUtil.getCurrentDeptRole();
            
            // 2. 查询用户有权限的知识库（自动权限过滤✅）
            TbAiKnowledge filter = new TbAiKnowledge();
            filter.setStatus(1); // 只查询启用的
            
            List<TbAiKnowledge> authorizedKnowledges = 
                knowledgeMapper.selectAiKnowledges(
                    filter, 
                    userDeptRoles  // 直接传入LoginUtil获取的用户权限信息
                );
            
            // 3. 提取Dify Dataset IDs
            List<String> datasetIds = authorizedKnowledges.stream()
                .map(TbAiKnowledge::getDifyDatasetId)
                .filter(Objects::nonNull)
                .collect(Collectors.toList());
            
            if (datasetIds.isEmpty()) {
                emitter.send("您当前没有可访问的知识库，无法进行对话。");
                emitter.complete();
                return;
            }
            
            // 4. 从多个知识库检索相关内容
            List<RetrievalRecord> retrievalRecords = 
                difyApiClient.retrieveFromMultipleDatasets(
                    message, 
                    datasetIds, 
                    5  // Top K
                );
            
            // 5. 构建上下文
            String context = buildContext(retrievalRecords, authorizedKnowledges);
            
            // 6. 调用LLM流式对话
            difyApiClient.streamChatWithContext(
                message,
                context,
                conversationId,
                userId,
                new StreamCallback() {
                    private StringBuilder fullAnswer = new StringBuilder();
                    
                    @Override
                    public void onChunk(String chunk) {
                        fullAnswer.append(chunk);
                        emitter.send(chunk);
                    }
                    
                    @Override
                    public void onComplete() {
                        // 保存消息
                        saveMessages(
                            conversationId, 
                            userId, 
                            message, 
                            fullAnswer.toString(),
                            retrievalRecords
                        );
                        emitter.complete();
                    }
                    
                    @Override
                    public void onError(Throwable error) {
                        log.error("对话失败", error);
                        emitter.completeWithError(error);
                    }
                }
            );
            
        } catch (Exception e) {
            log.error("流式对话异常", e);
            emitter.completeWithError(e);
        }
    }
    
    /**
     * 构建上下文
     */
    private String buildContext(
            List<RetrievalRecord> records,
            List<TbAiKnowledge> knowledges) {
        
        Map<String, String> knowledgeTitles = knowledges.stream()
            .collect(Collectors.toMap(
                TbAiKnowledge::getDifyDatasetId,
                TbAiKnowledge::getTitle
            ));
        
        return records.stream()
            .map(r -> {
                String datasetId = r.getDatasetId();
                String knowledgeTitle = knowledgeTitles.getOrDefault(datasetId, "未知知识库");
                return String.format(
                    "【来源：%s - %s】\n%s",
                    knowledgeTitle,
                    r.getDocumentName(),
                    r.getContent()
                );
            })
            .collect(Collectors.joining("\n\n---\n\n"));
    }
}
```

#### DifyApiClient实现

```java
@Component
public class DifyApiClient {
    
    @Autowired
    private DifyConfig difyConfig;
    
    private final OkHttpClient httpClient;
    
    public DifyApiClient(DifyConfig difyConfig) {
        this.difyConfig = difyConfig;
        this.httpClient = new OkHttpClient.Builder()
            .connectTimeout(difyConfig.getConnectTimeout(), TimeUnit.SECONDS)
            .readTimeout(difyConfig.getReadTimeout(), TimeUnit.SECONDS)
            .build();
    }
    
    /**
     * 从多个知识库检索
     */
    public List<RetrievalRecord> retrieveFromMultipleDatasets(
            String query,
            List<String> datasetIds,
            int topK) {
        
        // 并行检索所有知识库
        List<CompletableFuture<List<RetrievalRecord>>> futures = 
            datasetIds.stream()
                .map(id -> CompletableFuture.supplyAsync(() -> 
                    retrieveFromDataset(id, query, topK)
                ))
                .collect(Collectors.toList());
        
        // 等待完成
        CompletableFuture.allOf(futures.toArray(new CompletableFuture[0])).join();
        
        // 合并并排序
        return futures.stream()
            .map(CompletableFuture::join)
            .flatMap(List::stream)
            .sorted((a, b) -> Double.compare(b.getScore(), a.getScore()))
            .limit(topK)
            .collect(Collectors.toList());
    }
    
    /**
     * 从单个知识库检索
     */
    private List<RetrievalRecord> retrieveFromDataset(
            String datasetId, 
            String query, 
            int topK) {
        
        String url = String.format(
            "%s/datasets/%s/retrieve", 
            difyConfig.getApiBaseUrl(), 
            datasetId
        );
        
        JSONObject body = new JSONObject();
        body.put("query", query);
        body.put("top_k", topK);
        body.put("score_threshold", 0.7);
        
        Request request = new Request.Builder()
            .url(url)
            .header("Authorization", "Bearer " + difyConfig.getApiKey())
            .header("Content-Type", "application/json")
            .post(RequestBody.create(
                body.toString(), 
                MediaType.parse("application/json")
            ))
            .build();
        
        try (Response response = httpClient.newCall(request).execute()) {
            if (!response.isSuccessful()) {
                throw new DifyException("知识库检索失败: " + response.message());
            }
            
            String responseBody = response.body().string();
            return parseRetrievalResponse(datasetId, responseBody);
            
        } catch (IOException e) {
            throw new DifyException("知识库检索异常", e);
        }
    }
    
    /**
     * 流式对话（带上下文）
     */
    public void streamChatWithContext(
            String query,
            String context,
            String conversationId,
            String userId,
            StreamCallback callback) {
        
        String url = difyConfig.getApiBaseUrl() + "/chat-messages";
        
        // 构建完整Prompt
        String fullPrompt = String.format(
            "请基于以下知识库内容回答用户问题。" +
            "如果知识库中没有相关信息，请明确告知用户。\n\n" +
            "知识库内容：\n%s\n\n" +
            "用户问题：%s",
            context, query
        );
        
        JSONObject body = new JSONObject();
        body.put("query", fullPrompt);
        body.put("conversation_id", conversationId);
        body.put("user", userId);
        body.put("response_mode", "streaming");
        body.put("inputs", new JSONObject());
        
        Request request = new Request.Builder()
            .url(url)
            .header("Authorization", "Bearer " + difyConfig.getApiKey())
            .header("Content-Type", "application/json")
            .post(RequestBody.create(
                body.toString(), 
                MediaType.parse("application/json")
            ))
            .build();
        
        // SSE流式处理
        httpClient.newCall(request).enqueue(new Callback() {
            @Override
            public void onResponse(Call call, Response response) {
                if (!response.isSuccessful()) {
                    callback.onError(new DifyException("对话失败: " + response.message()));
                    return;
                }
                
                try (BufferedReader reader = new BufferedReader(
                        new InputStreamReader(response.body().byteStream()))) {
                    
                    String line;
                    while ((line = reader.readLine()) != null) {
                        if (line.startsWith("data: ")) {
                            String data = line.substring(6);
                            if (!"[DONE]".equals(data)) {
                                JSONObject json = new JSONObject(data);
                                String chunk = json.optString("answer", "");
                                if (!chunk.isEmpty()) {
                                    callback.onChunk(chunk);
                                }
                            }
                        }
                    }
                    callback.onComplete();
                    
                } catch (Exception e) {
                    callback.onError(e);
                }
            }
            
            @Override
            public void onFailure(Call call, IOException e) {
                callback.onError(e);
            }
        });
    }
}
```

---

## 📊 三种方式对比

| 方案 | 灵活性 | 实现难度 | 性能 | 推荐度 |
|------|--------|----------|------|--------|
| 检索API + 自定义LLM | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | ⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ |
| Workflow工作流 | ⭐⭐⭐⭐ | ⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐ |
| 多应用切换 | ⭐⭐ | ⭐ | ⭐⭐⭐ | ⭐ |

---

## 🎯 最终推荐方案

**使用"检索API + 自定义LLM"方案**

**理由**：
1. ✅ 完全控制知识库访问权限
2. ✅ 可以实现复杂的部门隔离逻辑
3. ✅ 支持并行检索多个知识库
4. ✅ 可以自定义Prompt和上下文
5. ✅ 灵活性最高，适合企业级应用

**实现步骤**：
1. 用户发起对话
2. 根据用户权限查询可访问的知识库（Mapper已实现✅）
3. 并行调用Dify检索API获取相关内容
4. 合并结果构建上下文
5. 调用LLM流式生成答案
6. 保存对话记录（含知识来源）

这样既利用了Dify的知识库能力，又保持了完全的控制权！🎉