Transform BeanUtils to achieve list data copy gracefully

Preface

BeanUtils.copyProperties(); It did do a lot for us , Although the deep copy cannot be completed perfectly , But for po、vo、dto A copy of is enough . But it still has some imperfections

• Insufficient ：

1. Can't copy list, And copy list There are a lot of cases , So there will be a lot of duplicate code .

for (S source : sources) {
    T target = new T();
    copyProperties(source, target);
    list.add(target);
}

2. There are some simple queries , You just need to switch vo Also needed new Vo()

public Vo findById(Integer id) {
 Vo vo = new Vo();
 Po po = dao.findById(id);
 copyProperties(po, vo);
 return vo;
}

3. This copy method has no return value , Now? jdk8 Support stream() After the operation ( Reference resources ：Jdk8 Stream), Support is not very friendly , inconvenient lambda Use of expressions .

So we decided to integrate BeanUtils class , Make yourself a handy wheel .

Use

We will create a new wheel BeanConvertUtils, Use as follows ：

When we're going to switch po、vo when , It only needs , in addition , official account Java selected , reply java interview , Obtain interview question information .

//  Before using 
public Vo findById(Integer id) {
 Vo vo = new Vo();
 Po po = dao.findById(id);
 copyProperties(po, vo);
 return vo;
}

//  After using 
public Vo findById(Integer id) {
 return BeanConvertUtils.converTo(dao.findById(id), Vo::new);
}

//  After using , adopt lambda Expressions deal specifically with individual fields 
public Vo findById(Integer id) {
 return BeanConvertUtils.converTo(dao.findById(id), Vo::new, 
  (s, t) -> t.setName(s.getName))
 );
}

When we want to copy list It's also very simple

//  Before using 
public List<Vo> findAll() {
 List<Vo> vos = new ArrayList();
 List<Po> pos = dao.findAll();
 for (Po po : Pos) {
     Vo vo = new Vo();
     BeanUtis.copyProperties(po, vo);
     vos.add(vo);
    }
 return vos;
}

//  After using 
public List<Vo> findAll() {
 return BeanConvertUtils.converToList(dao.findAll(), Vo::new)
}

//  It also supports customization lambda
public List<Vo> findAll() {
 return BeanConvertUtils.converToList(dao.findAll(), Vo::new,
  (s, t) -> t.setName(s.getName))
 )
}

Code

/**
 *  Convert object tool 
 *
 * @author bugpool
 */
public class BeanConvertUtils extends BeanUtils {

    public static <S, T> T convertTo(S source, Supplier<T> targetSupplier) {
        return convertTo(source, targetSupplier, null);
    }

    /**
     *  Convert objects , official account ：Java selected 
     *
     * @param source          Source object 
     * @param targetSupplier  Target object supplier 
     * @param callBack        The callback method 
     * @param <S>             Source object type 
     * @param <T>             Target object type 
     * @return  Target audience 
     */
    public static <S, T> T convertTo(S source, Supplier<T> targetSupplier, ConvertCallBack<S, T> callBack) {
        if (null == source || null == targetSupplier) {
            return null;
        }

        T target = targetSupplier.get();
        copyProperties(source, target);
        if (callBack != null) {
            callBack.callBack(source, target);
        }
        return target;
    }

    public static <S, T> List<T> convertListTo(List<S> sources, Supplier<T> targetSupplier) {
        return convertListTo(sources, targetSupplier, null);
    }

    /**
     *  Convert objects 
     *
     * @param sources         Source object list
     * @param targetSupplier  Target object supplier 
     * @param callBack        The callback method 
     * @param <S>             Source object type 
     * @param <T>             Target object type 
     * @return  Target audience list
     */
    public static <S, T> List<T> convertListTo(List<S> sources, Supplier<T> targetSupplier, ConvertCallBack<S, T> callBack) {
        if (null == sources || null == targetSupplier) {
            return null;
        }

        List<T> list = new ArrayList<>(sources.size());
        for (S source : sources) {
            T target = targetSupplier.get();
            copyProperties(source, target);
            if (callBack != null) {
                callBack.callBack(source, target);
            }
            list.add(target);
        }
        return list;
    }

    /**
     *  Callback interface   official account ：Java selected 
     *
     * @param <S>  Source object type 
     * @param <T>  Target object type 
     */
    @FunctionalInterface
    public interface ConvertCallBack<S, T> {
        void callBack(S t, T s);
    }
}

performance

Because only BeanUtils An encapsulation of , The performance is almost the same as that of the original code , If you want to say almost right , After all, there is an extra layer of function stack calls , But it is basically negligible . The main performance is still determined by BeanUtils decision .

remind

I don't know about this BeanConvertUtils How do you feel about tools , I used a lot in the project , Very convenient also . But there are two things to be reminded .

• This method still can not solve the deep copy problem , Detailed can google once BeanUtils Deep copy problem ;

• If source perhaps targetSupplier Just one for null, This tool class is not like BeanUtils Throw an exception like this , It's going back to null, Because I think that if the caller puts null Carry out quasi replacement , That is to convert to null, If it is not empty, it should be the responsibility of the caller .

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