AspectJ - 使用反射來實現非公共類的實體對象

Question

我想在AspectJ中實例化非公共類的對象。

我有這個類：

package ca1.business; 

public class Bill { 

    int id; 
    String idOperator; 
    String idClient; 

    Bill(int id, String idOperator, String idClient) { /* (...) */ } 
    public String toString() { /* (...) */ } 
    public boolean equals(Object o) { /* (...) */ } 
    public int getId() { /* (...) */ } 
    public String getOperator() { /* (...) */ } 
    public String getClient() { /* (...) */ } 
} 

在各方面類我希望能夠做到：

Bill b = new Bill(currInvoice, idOperator, idClient); 

的問題是，我得到一個錯誤：

The constructor Bill(int, String, String) is not visible 

所以我調查並試圖使用反射，就像它在this後的解釋。

try { 
    Constructor<Bill> cons = Bill.class.getDeclaredConstructor(null); 
    cons.setAccessible(true); 
    Bill invoice = cons.newInstance(null); 
    invoice.id = 1; 
    invoice.idOperator = "foo"; 
    invoice.idClient = "bar"; 
    // etc... 
} catch (SecurityException e) { 
    e.printStackTrace(); 
} catch (NoSuchMethodException e) { 
    e.printStackTrace(); 
} catch (IllegalArgumentException e) { 
    e.printStackTrace(); 
} catch (InstantiationException e) { 
    e.printStackTrace(); 
} catch (IllegalAccessException e) { 
    e.printStackTrace(); 
} catch (InvocationTargetException e) { 
    e.printStackTrace(); 
} 

但我得到的行錯誤：

invoice.id = 1; 
invoice.idOperator = "foo"; 
invoice.idClient = "bar"; 

的錯誤是：

The field Bill.X is not visible. 

有誰知道是否有什麼解決辦法？

Answer 1

爲什麼要使用反射？

讓我們假設Bill類看起來是這樣的：

package ca1.business; 

public class Bill { 
    int id; 
    String idOperator; 
    String idClient; 

    Bill(int id, String idOperator, String idClient) { 
    this.id = id; 
    this.idOperator = idOperator; 
    this.idClient = idClient; 
    } 

    @Override 
    public String toString() { 
    return "Bill [id=" + id + ", idOperator=" + idOperator + ", idClient=" + idClient + "]"; 
    } 

    public static Bill instance; 

    public static void main(String[] args) { 
    System.out.println(instance); 
    } 
} 

我們要執行之前main（愚蠢的例子，只是爲了演示）我們的方式來填充靜態成員：

選項A ：特權方面

package de.scrum_master.aspect; 

import ca1.business.Bill; 

public privileged aspect MyAspect { 
    before() : execution(public static void main(String[])) { 
    Bill.instance = new Bill(11, "operator", "client"); 
    } 
} 

賓得n B：將方面放入包ca1.business

構造函數是包私有的，即同一包中的其他類可以訪問它。

package ca1.business; 

public aspect MyAspect { 
    before() : execution(public static void main(String[])) { 
    Bill.instance = new Bill(11, "operator", "client"); 
    } 
} 

選項C：把工廠類爲保護包作爲輔助

package ca1.business; 

public class BillFactory { 
    public static Bill create(int id, String idOperator, String idClient) { 
    return new Bill(id, idOperator, idClient); 
    } 
} 

package de.scrum_master.aspect; 

import ca1.business.Bill; 
import ca1.business.BillFactory;; 

public aspect MyAspect { 
    before() : execution(public static void main(String[])) { 
    Bill.instance = BillFactory.create(11, "operator", "client"); 
    } 
} 

控制檯日誌每個選項A，B，C

Bill [id=11, idOperator=operator, idClient=client]