Copy POJO content from one bean to another

问题:

I have few Pojos in different packages, each POJO contains set of the another pojo from the same package. I need to copy all items with the same name from Package B Pojos to objects in Package A.

Eaxmple:

package com.vanilla.packageA;

public class Student{

    private String firstName;
    private String lastName;
    private Set<Course> course;

    //getters and setters ommited

}   

---

package com.vanilla.packageA;

    public class Course{
    private String courseName;
    private String courseDescription;

    //seters and getters
}

---

package com.vanilla.packageB;

public class Student{

    private String firstName;
    private String lastName;
    private Address address;
    private Set<Course> course;
    Private Date birtday;

    //getters and setters ommited

}   

---

package com.vanilla.packageB;

public class Course{
    private String courseName;
    private String courseDescription;
    private <Lecturer> lecturer;
    private Integer hours;

    //seters and getters
} 

I want to copy recursively all items from PackageB classes to packageA classes which exists in PaCkageB and shares the same name.

Updates:

Guys, I understand that that this is stupid question, but I need to maintain this code, now the code is written in the way that they have to call 50 getters and setter, or calling constructor with 50 parameters. Unfortunately, I can't use the same object and I need to copy it, but I must find more "elegant" way to copy tese beans.

回答1:

Any reason why Apache BeanUtils.copyProperties does not work?

回答2:

Well.. Dozer may be just the thing you're looking for.

. . . its an object to object mapping framework. The idea is that:

• Usually it will map by convention.
• You can override this convention with a mapping file.

. . therefore mapping files are as compact as possible. Its useful for many cases, such as mapping a use-case specify service payload on to the reusable core model objects.

When delivering the SpringSource training courses we used to point out this framework very often.

回答3:

See to mapstruct. This tools generates code, so there is no overhead on reflection.

回答4:

Copying fields values are a need I almost every project, for example for do the clone(). I also think that for accomplish some goals isn't necessary import .jars for using only one function. I would like share some little code in which I was working, there are some things that I left in the inkwell but in general it do the work. In this case I use reflection.

public class ObjectCopyTools {

static String[] bases = new String[] {"byte", "short", "int", "long", "float", "double", "char", "boolean"};
static String[] equivalents = new String[] {"Byte", "Short", "Integer", "Long", "Float", "Double", "Character", "Boolean"};

static {

}

private static boolean areEquivalents(String type1, String type2){
    for (int i = 0; i < bases.length; i++) {
        if((type1.equals(bases[i]) && type2.equals(equivalents[i])) 
                || (type2.equals(bases[i]) && type1.equals(equivalents[i]))){
            return true;
        }
    }
    return false;
}

public static <T extends Object, Y extends Object> Y deepReflectionObjectCopy(T origin, Class<Y> resultClass) {
    Class<? extends Object> origClass = origin.getClass();
    Y resultObject = null;
    for (Constructor<?> constructor : resultClass.getConstructors()) {
        if (constructor.getParameterCount() == 0) {
            try {
                resultObject = (Y) constructor.newInstance();
            }catch (InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
            }
            break;
        }
    }
    if(resultObject == null){
        return null;
    }
    Field[] origFields = origClass.getDeclaredFields();
    Field[] destFields = resultObject.getClass().getDeclaredFields();

    Object value = null;
    for(Field dstField: destFields){
        try {
            Field tempOrigField = origClass.getDeclaredField(dstField.getName());
            if(tempOrigField.getType().equals(dstField.getType())
                    || areEquivalents(tempOrigField.getType().getSimpleName(), dstField.getType().getSimpleName())){
                dstField.set(resultObject, tempOrigField.get(origin));
            }
        } catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
        }
    }
    return resultObject;
}

Hope this help.

回答5:

If DRY is a bedrock principle of computer science, what reason can you give for two identical, parallel object graphs? Not only have you doubled your maintenance burden, but now you have to develop a recursive method to do nothing but ferry data from one to the other.