如何为独立的Java应用程序存储简单数据

Question

Assume I have a long list of People with some basic characteristics:

Matt, 27, male

Anne, 49, female

etc...

I want to store this data locally for a standalone desktop application that does not require access to the internet. My current method is writing the names to a json file and reading them all in to a Person class in java when the program is opened; however, I did not think this was efficient as the data only needs to be accessed if someone is performing a search.

So I considered a simple JSONparser, let's say searchNameInFile("Matt", "data.json") { return person; }, but I did not know if this was a good way to store the data with regards to efficiency. I considered sqlite shortly, but I am only storing one table of data and thought it might be overkill. What is an appropriate, efficient method for storing and searching local data?

Answer 1

I really think you should reconsider SQLite.

https://www.tutorialspoint.com/sqlite/sqlite_java.htm

Your data will be stored locally in a file that can be easily queried with standard Java SQL stuff. It does not require any server software or an internet connection.

If you don't want to use SQLite, here are two possible ways, depending on what you do care about.

If you only care about time complexity, but have plenty of memory to throw around, you could store your data in an efficient structure such as a HashMap, and use Java's built in Serializable to write the HashMap out to a file, and read it back in on next start.

//Where Person is a data class that implements Serializable and contains your desired fields
public void saveData(HashMap<String, Person> people) {
    FileOutputStream f = new FileOutputStream(new File("people.txt"));
    ObjectOutputStream o = new ObjectOutputStream(f);
    o.writeObject(people);
    o.close();
    f.close();
}
public HashMap<String, Person> loadData() {
    FileInputStream fi = new FileInputStream(new File("people.txt"));
    ObjectInputStream oi = new ObjectInputStream(fi);
    HashMap<String, Person> data = (HashMap<String, Person>) oi.readObject();
    oi.close();
    fi.close();
    return data;
}

If you don't mind O(n) search times, then your current solution of re-reading the file on every search is fine.

Answer 2

You can also consider another Simple in-memory DB as H2. It will save data in a relational db that is store in your computer as a file. The advantage is the high-retrieval speed benchmark it has. H2

Advantage is that configuration is as simple as create the DB object and configure it to use in-memory file.

Answer 3

it might be overkill

Re-inventing the wheel would be the real overkill. There are plenty libraries and methods out there for storing and loading data.

Since you want to store the data locally in a file, but also want to search in the data, an embedded SQL database should be a good option for you. Either SQLite, h2 or HSQL.

For acessing the data, you can use anything from plain JDBC up to Spring Data JPA