将字符串转换为适当的 Java 对象

Question

我有一个这种格式的字符串（包括大括号）：

{id=123, vehicle_name=Tesla Model X, price=80000.00, ... }

什么是合适的Java对象来表示这个字符串，我怎样才能把它转换成那个对象？

我希望能够查询对象以轻松检索其值，例如。 obj.get("vehicle_name")。我尝试使用 JSONObject 将其转换为 JSON，但是这需要冒号作为键和值之间的分隔符，而不是等号。

Answer 1

• String 本身是一个 java 对象。
• 解析字符串并填充 java 对象不干净。
• 您可以创建一个 java pojo Vehicle，其属性如 id， 车辆名称等。假设您的字符串将始终遵循相同的 模式。
• 解析字符串，并填写此 Vehicle pojo。

下面只是一个简单的例子，关于如何做到这一点：-

public class Test {

    public static void main(String[] args){
        String text="{id=123, vehicle_name=Tesla Model X, price=80000.00}";
        text=text.replaceAll("[{}]", "");
        String[] commaDelimitArray=text.split(",");
        Vehicle vehicle=new Vehicle();
        for(int i=0;i<commaDelimitArray.length;i++){

            String[] keyValuePair=commaDelimitArray[i].split("=");
            String key=keyValuePair[0].trim();
            String value=keyValuePair[1].trim();
            if("id".equals(key)){
                vehicle.setId(value);
            }
            else if("vehicle_name".equals(key)){
                vehicle.setVehicleName(value);
            }
            else if("price".equals(key)){
                vehicle.setPrice(value);
            }
        }
        System.out.println(vehicle.getId()+" |"+vehicle.getVehicleName());
    }

    static class Vehicle{
        private String id;
        private String vehicleName;
        private String price;
        public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id;
        }
        public String getVehicleName() {
            return vehicleName;
        }
        public void setVehicleName(String vehicleName) {
            this.vehicleName = vehicleName;
        }
        public String getPrice() {
            return price;
        }
        public void setPrice(String price) {
            this.price = price;
        }

    }

}

Answer 2

这似乎是创建 Object 类的任务。如果是这样，你想创建这样的东西：

public class Car {

    int id;
    String name;
    double price;
    //include any other necessary variables

    public Car(int id, String name, double price) {
        this.id = id;
        this.name = name;
        this.price = price;
        //include any other variables in constructor header and body
    }

    public void setID(int newID) {
        id = newID;
    }

    public int getID() {
        return id;
    }

    //add getters and setters for other variables in this same manner
}

请注意，您也可以创建一个不带参数并将变量初始化为默认值的构造函数，然后使用 setter 方法单独设置值。

在您的主类中，您要做的是从您的 String 中提取适当的子字符串以传递给构造函数（或 setter）。有多种方法可以做到这一点（你可以阅读一些方法here）；我个人建议使用regular expressions and a Matcher。

Answer 3

如果我有这样一个需要转换为对象的字符串，我将创建一个具有返回 Vehicle 对象的静态方法的类。然后你可以对那个对象做任何你想做的事情。几个 getter 和 setter 就可以了。

如果我理解了您的问题，我已经提出了一些代码，它应该可以按您的预期工作:)

有很多 cmets，所以这应该可以帮助您理解代码逻辑。

Vehicle 类是在名为 createVehicle(String keyValueString) 的静态方法中进行所有解析的地方。

主类：

import java.util.ArrayList;
import java.util.List;

public class main {

    public static void main(String[] args) {

        String vehicleString = "{id=123, vehicle_name=Tesla Model X, price=80000.00}";
        List<Vehicle> vehicles = new ArrayList<Vehicle>();
        Vehicle vehicle;

        // call the static method passing the string for one vehicle
        vehicle = Vehicle.createVehicle(vehicleString);

        // if the id is -1, then the default constructor fired since
        // there was an error when parsing the code.
        if(vehicle.getId() == -1 ) {
            System.out.println("Check your data buddy.");
        } else {
            vehicles.add(vehicle);
        }

        for(Vehicle v : vehicles){
            System.out.println("Vehicle id: " + v.getId());
            System.out.println("Vehicle name: " + v.getVehicle_name());
            System.out.println("Vehicle price: " + v.getPrice());
            System.out.println();
        }
    }
}

车辆类别：

import java.math.BigDecimal;

public class Vehicle {

    // declare your attributes mapped to your string
    private int id;
    private String vehicle_name;
    private BigDecimal price;

    // Start Constructor
    // Default Constructor
    public Vehicle() {
        this.setId(-1);
        this.setVehicle_name("Empty");
        this.setPrice(new BigDecimal(0.00));
    }

    public Vehicle(int id, String vehicle_name, BigDecimal price) {
        this.setId(id);
        this.setVehicle_name(vehicle_name);
        this.setPrice(price);
    }
    // End Constructor

    // Start Getters and Setters
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getVehicle_name() {
        return vehicle_name;
    }

    public void setVehicle_name(String vehicle_name) {
        this.vehicle_name = vehicle_name;
    }

    public BigDecimal getPrice() {
        return price;
    }

    public void setPrice(BigDecimal price) {
        this.price = price;
    }

    // End Getters and Setters.

    // Start Methods and Functions

    // Given a string returns a string array split by a "," and with
    // "{}" removed.
    private static String[] splitString(String keyValueString) {
        String[] split;

        // Clean string from unwanted values
        keyValueString = keyValueString.replaceAll("[{}]", "");
        split = keyValueString.split(",");

        return split;
    }

    // Add a vehicle given a formatted string with key value pairs 
    public static Vehicle createVehicle(String keyValueString) {
        int id = 0;
        String vehicle_name = "";
        BigDecimal price = null;
        String[] split;
        Vehicle vehicle;
        split = splitString(keyValueString);

        // Loop through each keyValue array
        for(String keyValueJoined : split){
            // split the keyValue again using the "="
            String[] keyValue = keyValueJoined.split("=");
            // remove white space and add to a String variable
            String key = keyValue[0].trim();
            String value = keyValue[1].trim();

            // check which attribute you currently have and add
            // to the appropriate variable
            switch(key){
                case "id":
                    id = Integer.parseInt(value);
                    break;
                case "vehicle_name":
                    vehicle_name = value;
                    break;
                case "price":
                    try {
                        price = new BigDecimal(Double.parseDouble(value));
                    } catch (NumberFormatException e) {
                        e.printStackTrace();
                    }
                    break;
                default:
                    System.out.println("Attribute not available");
                    return null;                    
            }
        }
        // if any of the values have not been changed then either the
        // data is incomplete or inconsistent so return the default constructor.
        // Can be removed or changed if you expected incomplete data. It all 
        // depends how you would like to handle this.
        if(id == 0 || vehicle_name.equals("") || price == null){
            vehicle = new Vehicle();
        } else {
            //System.out.println(id);
            vehicle = new Vehicle(id, vehicle_name, price);
        }

        return vehicle;
    }
    // End Methods and Functions
}

给定提供的字符串，程序在使用 getter 访问新创建的对象属性时返回以下内容：

车辆编号：123

车辆名称：特斯拉 Model X

车辆 价格：80000

希望这会有所帮助。