如何读取jedis中某个键的json值？

Question

我有一个代码，我需要使用 Jedis 获取键“product_id”的 json 值，但我不知道 jedis.get() 操作是否可以直接输出 json。这是下面的代码。

Jedis jedis = pool.getResource();
    jedis.select(1);
    String attributeName = jedis.get(facet);
    jedis.select(0);
    JSONObject productJson =  jedis.get(productID);
    String attributeValue = productJson.getString(attributeName);

Answer 1

您可以使用

String redisCachedJSON = jedis.get(productId);

从 Redis 获取字符串 JSON

然后您可以使用此字符串创建 JSONObject

JSONObject jsonObject = new JSONObject(redisCachedJSON);

请记住，Jedis 上的

get()

期望存储在该键上的值是字符串表示形式。

我不太确定你的对象是什么，但我们假设 json 如下：

// Product json String
{
   "id" : 1,
   "price" : "2.63",
   "quantity" : 25,
   "attributeName" : "attributeValue",
}

您可以将 JSON 映射到比 HashMap 更容易处理的 Java 类（除非您的 json 键动态更改），并使用 Gson

将 json 字符串映射到该类的对象

public Class Product {
       int id;
       String price;
       int quantity;
       String attributeName;
}

String redisCachedJSON= jedis.get(productId);
Product product = new Gson().fromJson(redisCachedJSON, Product.class);
System.out.println(product.attributeName); // attributeValue

您也可以使用 JsonObjectMapper 来做到这一点

ObjectMapper objectMapper = new ObjectMapper();
Product product = objectMapper.readValue(redisCachedJSON, Product.class);

Answer 2

Redis 可以存储和索引 JSON 文档。 安装 Redis Stack 并找到 examples。按照示例学习如何将会话作为 JSON 文档进行管理，以及如何在会话内和跨会话中执行搜索

    HostAndPort node = HostAndPort.from("localhost:6379");
    JedisClientConfig clientConfig = DefaultJedisClientConfig.builder()
                                        .resp3() // RESP3 protocol
                                        .build();

    UnifiedJedis client = new UnifiedJedis(node, clientConfig);
    
    // Drop the index and all the indexed documents
    client.ftDropIndexDD("session_idx");
    
    // Modeling a shopping cart as JSON using Jedis
    Schema schema = new Schema()
                .addGeoField("$.location").as("location")
                .addTagField("$.cart[*].id").as("item_id")
                .addNumericField("$.cart[*].price").as("price")
                .addTagField("$.visited[*]").as("visited")
                .addNumericField("$.lastAccessedTime").as("updated")
                .addNumericField("$.creationTime").as("created");
    
    // Defining the index, it could be HASH too
    IndexDefinition def = new IndexDefinition(Type.JSON).setPrefixes(new String[] {"session:"});
    
    // Creating the index 
    client.ftCreate("session_idx", IndexOptions.defaultOptions().setDefinition(def), schema);
    
    // Some initial data
    JSONObject jsonObject = new JSONObject();
    jsonObject.put("lastAccessedTime", System.currentTimeMillis() / 1000L);
    jsonObject.put("creationTime", System.currentTimeMillis() / 1000L);
    jsonObject.put("location", "34.638,31.79");
    client.jsonSet("session:1", jsonObject);
    
    
    // Storing a list of visited URLs
    client.jsonSet("session:1", new Path2("visited"), new ArrayList<>());
    List<String> visited = new ArrayList<String>();
    visited.add("www.redis.io");
    visited.add("www.wikipedia.com");
    visited.add("www.mortensi.com");
    client.jsonSetWithEscape("session:1", new Path2("visited"), visited);

    // Shopping cart item
    JSONObject laptop = new JSONObject();
    laptop.put("id", "hp-2341");
    laptop.put("price", 1990.99);
    laptop.put("quantity", 1);

    // Another shopping cart item
    JSONObject laptopCase = new JSONObject();
    laptopCase.put("id", "case-9993");
    laptopCase.put("price", 19.99);
    laptopCase.put("quantity", 2);
    
    // Storing items in the shopping cart
    client.jsonSet("session:1", new Path2("cart"), new ArrayList<>());
    client.jsonArrAppend("session:1", new Path2("cart"), laptop);
    client.jsonArrAppend("session:1", new Path2("cart"), laptopCase);
    
    // Read the JSON document
    System.out.println(client.jsonGet("session:1"));
    
    // Read part of the document
    System.out.println(client.jsonGet("session:1", new Path2("$.cart")));
    
    // Search within a document
    System.out.println(client.jsonGet("session:1", new Path2("$.cart[?(@.id==\"hp-2341\")].price")));
    
    // Creating another session
    JSONObject jsonObject2 = new JSONObject();
    jsonObject2.put("lastAccessedTime", System.currentTimeMillis() / 1000L);
    jsonObject2.put("creationTime", System.currentTimeMillis() / 1000L);
    jsonObject2.put("location", "34.638,31.79");
    client.jsonSet("session:2", jsonObject2);
    
    // Shopping cart item
    JSONObject book = new JSONObject();
    book.put("id", "sking-2435");
    book.put("price", 14.90);
    book.put("quantity", 1);

    client.jsonSet("session:2", new Path2("cart"), new ArrayList<>());
    client.jsonArrAppend("session:2", new Path2("cart"), book);

    // Search
    Query q = new Query().addFilter(new Query.NumericFilter("price", 10, 30)).setSortBy("price", true).setNoContent();
    SearchResult res = client.ftSearch("session_idx", q);
    System.out.println("Number of results: " + res.getTotalResults());
    List<Document> docs = res.getDocuments();
    
    for (Document doc : docs) {
        System.out.println("Found session: " + doc.getId()); 
    }