学习初衷

• 用于满足自己的测试要求，不连接数据库，也不在意数据丢失

准备

1. maven依赖
   
   org.springframework.boot
   spring-boot-starter-test
   test
   

代码实现

1. 内存数据库（InMemoryDatabase）

• 使用了单例模式，程序启动就创建

package com.kwan.springbootkwan.test.lykj;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class InMemoryDatabase {
    private static InMemoryDatabase instance;
    public final Map<String, HashMap<String, String>> database;

    private InMemoryDatabase() {
        this.database = new HashMap<>();
    }

    public static synchronized InMemoryDatabase getInstance() {
        if (instance == null) {
            instance = new InMemoryDatabase();
        }
        return instance;
    }

    public void insert(String tableName, String primaryKey, String data) throws JsonProcessingException {


        if (!database.containsKey(tableName)) {
            database.put(tableName, new HashMap<String,String>());
        }
        database.get(tableName).put(primaryKey, data);
    }

    public Object query(String tableName, String primaryKey, Class<?> clazz) throws JsonProcessingException {
        Set<String> tableSet = database.keySet();
        if (!tableSet.contains(tableName)) {
            return null;
        }
        String jsonData = database.get(tableName).get(primaryKey);
        if (jsonData == null) {
            return null;
        }
        ObjectMapper mapper = new ObjectMapper();
        return mapper.readValue(jsonData, clazz);
    }

    public String delete(String tableName, String primaryKey) {
        return database.get(tableName).remove(primaryKey);
    }

    public void update(String tableName, String primaryKey, String updatedJsonData) {
        Map<String, String> table = database.get(tableName);

        if (table != null) {
            table.put(primaryKey, updatedJsonData);
        } else {
            throw new IllegalArgumentException("Table " + tableName + " does not exist.");
        }
    }
}

2. 测试增删改查方法

package com.kwan.springbootkwan.test.lykj.memorydb;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

public class InMemoryDatabase {
    private static InMemoryDatabase instance;
    public final Map<String, HashMap<String, String>> database;

    private InMemoryDatabase() {
        this.database = new HashMap<>();
    }

    public static synchronized InMemoryDatabase getInstance() {
        if (instance == null) {
            instance = new InMemoryDatabase();
        }
        return instance;
    }

    public void insert(String tableName, String primaryKey, String data) throws JsonProcessingException {


        if (!database.containsKey(tableName)) {
            database.put(tableName, new HashMap<String,String>());
        }
        database.get(tableName).put(primaryKey, data);
    }

    public Object query(String tableName, String primaryKey, Class<?> clazz) throws JsonProcessingException {
        Set<String> tableSet = database.keySet();
        if (!tableSet.contains(tableName)) {
            return null;
        }
        String jsonData = database.get(tableName).get(primaryKey);
        if (jsonData == null) {
            return null;
        }
        ObjectMapper mapper = new ObjectMapper();
        return mapper.readValue(jsonData, clazz);
    }

    public String delete(String tableName, String primaryKey) {
        return database.get(tableName).remove(primaryKey);
    }

    public void update(String tableName, String primaryKey, String updatedJsonData) {
        Map<String, String> table = database.get(tableName);

        if (table != null) {
            table.put(primaryKey, updatedJsonData);
        } else {
            throw new IllegalArgumentException("Table " + tableName + " does not exist.");
        }
    }
}

结果

感谢阅读

感谢您阅读 这篇文章，我们探索了自己本地模拟内存数据库增删改查
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