CODEWITHSUNDEEP
javajson
Arvind Carpenter
Arvind Carpenter

Reputation: 48

Convert A JSON file into java objects when web server starts

I have one JSON file i am converting it to JAVA Object using Object Mapper as given below :-

String agentName = Request.getAgentName();
ObjectMapper mapper = new ObjectMapper();
agent = mapper.readValue(new File(agentName), Agent.class);

these is working fine, but the problem is, for each and every request i am converting json to java object, I want to do it one time when my web server starts. How can i do it, these is a rest application.

Upvotes: 0

Views: 119

Answers (3)

Arvind Carpenter
Arvind Carpenter

Reputation: 48

I think these will work, i will create an object of agents class in my ServletContextListner class and under the method contextInitialized, i will create object of agents class by passing the list of all the agents.

import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.ipaylabs.eme.vo.main.Agent;

public class Agents {
    private static Agents theInstance;
    private static Map<String, Agent> AGENTS_MAP;

    public Agents(String[] agentList) {
        this.AGENTS_MAP = new HashMap<>();
        for(String agentName : agentList) {
            initAgent(agentName);
        } 
    }

    public Agent getAgent(String agentName) {
        if (!AGENTS_MAP.containsKey(agentName)) {
            initAgent(agentName);
        }
        return AGENTS_MAP.get(agentName);
    }


    private static void initAgent(String agentName) {
        ObjectMapper mapper = new ObjectMapper();
        Agent agent = null;
        try {
            agent = mapper.readValue(new File(agentName), Agent.class);
        } catch (JsonParseException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JsonMappingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        AGENTS_MAP.put(agentName, agent);
    }
}

Upvotes: 0

noiaverbale
noiaverbale

Reputation: 1688

This could be a possible solution using a Singleton class with a map holding all your agents initialized on request.

public class Agents {

    private static Agents theInstance;

    private final Map<String, Agent> AGENTS_MAP;

    private Agents() {
        this.AGENTS_MAP = new HashMap<>();
    }

    public static Agents getInstance() {
        if (theInstance == null) {
            theInstance = new Agents();
        }

        return theInstance;
    }

    public Agent getAgent(String agentName) {
        if (!AGENTS_MAP.containsKey(agentName) {
            initAgent(agentName);
        }

        return AGENTS_MAP.get(agentName);
    }

    // TODO handle errors
    private static void initAgent(String agentName) {
        ObjectMapper mapper = new ObjectMapper();
        Agent agent = mapper.readValue(new File(agentName), Agent.class);
        AGENTS_MAP.put(agentName, agent);
    }
}

Upvotes: 1

Mohsen
Mohsen

Reputation: 4643

You can use @PostConstruct to initialization of your variables:

@PostConstruct 
public void initApplication() {
    String agentName = Request.getAgentName();
    ObjectMapper mapper = new ObjectMapper();
    agent = mapper.readValue(new File(agentName), Agent.class); 
}

Upvotes: 0

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