从不同的包访问变量

Question

I want to access the variable in package 1 from package 2.

Class file TestDriver.java from package 1

public class TestDriver {
private static TestDriver instance = new TestDriver();
private static int check;
private static int envt_num;
public static String envt,port,cpy_key;

public Connection con;
private ManageDBConnection mdbc;

private static String ENCRYPTION_KEY = "0123456789abcdef";

public void TestDriver(){
    check = 20;
    Properties prop = new Properties();
    String propFileName = "properties/environment.properties";
    try{
    InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream(propFileName);
    System.out.println(inputStream);
    if (inputStream != null) {
        prop.load(inputStream);
        envt = prop.getProperty("envt");
        port = prop.getProperty("port");
        cpy_key = prop.getProperty("cpy_key");
        System.out.println("http://"+envt+"/netprofile/");  
        //Original Login Link
    /*  Constants.driver.get("http://"+prop.getProperty("user").replaceAll("\\s","")+":"+NP_Decrypt.getPassword().replaceAll("\\s","")+"@"+envt+"/netprofile/");
        inputStream.close();*/
        //Added for Local Testing
       String user = prop.getProperty("user");
       String password = prop.getProperty("password");
       Constants.driver.get("http://" + user + ":" + password + "@" + envt + "/test/");


    //  mdbc = new ManageDBConnection();
        //con = mdbc.CreateConnection();
    } else {
        throw new FileNotFoundException("property file '" + propFileName + "' not found in the classpath");
    }
    }catch(Exception e){
        e.printStackTrace();
    }   
}

}

Class file Constants.java from package 2

 public class Constants 
{
 static Properties prop = new Properties();
// propFileName = "properties/environment.properties";
//TestDriver testdriver = new TestDriver();
 static String envt = TestDriver.envt;
 static String cpy_key = TestDriver.cpy_key;


 //public static final 

 public static final WebDriver driver   = new FirefoxDriver();      

 public static final String InventorySummaryURL     ="http://"+envt+"/test/npHome.do?cpyKey="+cpy_key+"&custId=&grpId=0";    
 public static final String HomeSummary             ="http://"+envt+"/test/npIndex.do?cpyKey="+cpy_key+"&custId=&grpId=0";
 public static final String UploadStatus            ="http://"+envt+"/test/downloadModuleStatus.do?cpyKey="+cpy_key+"&custId=&grpId=0" ;
 public static final String ProfileStatus           ="http://"+envt+"/test/myProfileStatus.do?cpyKey="+cpy_key+"&custId=&grpId=0";

}

In Constants.java the value returned for envt and cpy_key is zero. I want the value from Package 1.

Answer 1

Main issue is that you're confusing static fields with instance fields, if the following variables:

private static final int check;
private static final int envt_num;
private static final String user, password;
public static String envt,port,cpy_key;

are the same across the JVM, don't modify them in a instance constructor, instead you can can create an static block to update the values of them and also, you can mark them as final if the are not supposed to be changed.

public final static String envt,port,cpy_key;

static {
    Properties prop = new Properties();
    String propFileName = "properties/environment.properties";
    try{
        InputStream inputStream = this.getClass().getClassLoader().getResourceAsStream(propFileName);
        System.out.println(inputStream);
        if (inputStream != null) {
           prop.load(inputStream);
           envt = prop.getProperty("envt");
           port = prop.getProperty("port");
           cpy_key = prop.getProperty("cpy_key");
          System.out.println("http://"+envt+"/netprofile/");  
          //Original Login Link
          /*        Constants.driver.get("http://"+prop.getProperty("user").replaceAll("\\s","")+":"+NP_Decrypt.getPassword().replaceAll("\\s","")+"@"+envt+"/netprofile/");
          inputStream.close();*/
          //Added for Local Testing
          user = prop.getProperty("user");
         password = prop.getProperty("password");

        } else {
         throw new FileNotFoundException("property file '" + propFileName + "' not found in the classpath");
        }
}

    public void TestDriver(){
         Constants.driver.get("http://" + user + ":" + password + "@" + envt + "/test/");


//  mdbc = new ManageDBConnection();
    //con = mdbc.CreateConnection();
}

The key is to separate what is static field vs what is an instance fields, the issue you had was the the static field wasn't being initialized when the class was loaded, but when the instance was created.

• Jose Luis

Answer 2

The variables envt and cpy_key are declaired static but shouldn't be. By declaring a variable to be static, you are telling the compiler/outside developers that this class doesn't have to be instantiated before you use that variable.

In your code, the envt and cpy_key variables are only initialized in the constructor of the TestDriver class. When you reference them from another class without instantiating a TestDriver you are getting a null value which is sometimes mapped to 0.

What you can do is:

1. Remove the static identifier from the envt and cpy_key variables, since you need to instantiate the TestDriver class before they able to be used.
2. Move the initialization code out of the constructor and use a static initialization block

Example:

public class TestDriver {
private static TestDriver instance = new TestDriver();
private static int check;
private static int envt_num;
public static String envt,port,cpy_key;

public Connection con;
private ManageDBConnection mdbc;

private static String ENCRYPTION_KEY = "0123456789abcdef";

static {
    check = 20;
    Properties prop = new Properties();
    String propFileName = "properties/environment.properties";
    try{
    InputStream inputStream = TestDriver.getClass().getClassLoader().getResourceAsStream(propFileName);
    System.out.println(inputStream);
    if (inputStream != null) {
        prop.load(inputStream);
        envt = prop.getProperty("envt");
        port = prop.getProperty("port");
        cpy_key = prop.getProperty("cpy_key");
        System.out.println("http://"+envt+"/netprofile/");  
        //Original Login Link
    /*      Constants.driver.get("http://"+prop.getProperty("user").replaceAll("\\s","")+":"+NP_Decrypt.getPassword().replaceAll("\\s","")+"@"+envt+"/netprofile/");
        inputStream.close();*/
        //Added for Local Testing
       String user = prop.getProperty("user");
       String password = prop.getProperty("password");
       Constants.driver.get("http://" + user + ":" + password + "@" + envt + "/test/");


    //  mdbc = new ManageDBConnection();
        //con = mdbc.CreateConnection();
    } else {
        throw new FileNotFoundException("property file '" + propFileName + "' not found in the classpath");
    }
    }catch(Exception e){
        e.printStackTrace();
    }   
}

So that fixes your initialization problem, but that doesn't solve your bigger class design problem. You should figure out a better (more Object Oriented) way of handling data. You have two classes relying on each other's static variables. This is a baaaad plan. I would advise you to encapsulate the variables that need initializing and keep them in the TestDriver class. Constants classes really should only be for things that you know ahead of time (hash key labels, numerical constants, etc).