如何使用Jedis读取JSON中指定键对应的值？

Hey there! Let's sort out your Jedis code issue quickly. The key thing you're missing here is that jedis.get() returns a plain String, not a ready-to-use JSONObject—so your current code will throw a compilation error right where you try to assign the result of jedis.get(productID) to a JSONObject variable.

Here's what's going wrong in your original code: #

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);

• jedis.get(productID) returns a String (the JSON data stored in Redis), but you're trying to assign it directly to a JSONObject reference—this won't work.
• Also, it's good practice to handle resource cleanup for Jedis (to avoid connection leaks) and add error handling for invalid JSON.

Corrected Code Example #

Let's use Alibaba's FastJSON (a common JSON library for Java) to parse the string into a JSONObject. First, make sure you have the FastJSON dependency in your project. Then:

// Use try-with-resources to auto-close the Jedis connection
try (Jedis jedis = pool.getResource()) {
    // Get attribute name from DB 1
    jedis.select(1);
    String attributeName = jedis.get(facet);
    
    // Get product JSON string from DB 0
    jedis.select(0);
    String productJsonString = jedis.get(productID);
    
    // Check if the JSON string exists before parsing
    if (productJsonString == null) {
        throw new IllegalArgumentException("No product found with ID: " + productID);
    }
    
    // Parse the string into a JSONObject
    JSONObject productJson = JSONObject.parseObject(productJsonString);
    
    // Retrieve the attribute value
    String attributeValue = productJson.getString(attributeName);
    // Do something with attributeValue here
} catch (JSONException e) {
    // Handle invalid JSON format error
    e.printStackTrace();
}

Key Notes: #

• Ensure Redis stores valid JSON: The value associated with productID in Redis must be a properly formatted JSON string. If it's not, the parse step will fail.
• Alternative libraries: If you prefer Jackson instead of FastJSON, you can use ObjectMapper to parse the string:

  ObjectMapper mapper = new ObjectMapper();
  JSONObject productJson = mapper.readValue(productJsonString, JSONObject.class);
  

• Resource management: Using try-with-resources ensures the Jedis connection is returned to the pool properly, preventing resource leaks.

内容的提问来源于stack exchange，提问作者vkaul11