使用BeanUtils类实现DTO之间的属性复制

Posted 2021-02-10 lgjlife

开发中经常碰到这样的场景，从数据库查询出来全部的字段，但是有些字段是不想给

客户端看到，这时就需要将属性从DAO复制到传给客户端的DTO对象，如果采用get/set，

那显得很麻烦。可使用反射实现。

 

Spring框架的  org.springframework.beans.BeanUtils 类帮我们实现了这个功能。

例子

@Data
class Source{

    private String  name;
    private int     age;

    public Source(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

@Data
class Source1{

    private String  home;
    private boolean  flag;

    public Source1(String home, boolean flag) {
        this.home = home;
        this.flag = flag;
    }
}

@Data
class Target{
    private String  name;
    private int     age;
    private String  home;
    private boolean  flag;

}

测试

@Slf4j
public class UserInfoDto {

    public static void main(String args[]){
        Source source = new Source("libai",34);
        Source1 source1 = new Source1("nanning",true);
        Target target = new Target();
        BeanUtils.copyProperties(source,target);
        BeanUtils.copyProperties(source1,target);


        log.debug("target = {}",target);
    }
}

输出

15:19:33.992 [main] DEBUG com.cloud.microblog.gateway.dto.UserInfoDto - target = Target(name=libai, age=34, home=nanning, flag=true)

需要注意的是，每个Bean类的getter/setter方法必须实现。

 

实现源码

private static void copyProperties(Object source, Object target, @Nullable Class<?> editable, @Nullable String... ignoreProperties) throws BeansException {
        Assert.notNull(source, "Source must not be null");
        Assert.notNull(target, "Target must not be null");
        Class<?> actualEditable = target.getClass();
        if (editable != null) {
            if (!editable.isInstance(target)) {
                throw new IllegalArgumentException("Target class [" + target.getClass().getName() + "] not assignable to Editable class [" + editable.getName() + "]");
            }

            actualEditable = editable;
        }

        PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);
        List<String> ignoreList = ignoreProperties != null ? Arrays.asList(ignoreProperties) : null;
        PropertyDescriptor[] var7 = targetPds;
        int var8 = targetPds.length;

        for(int var9 = 0; var9 < var8; ++var9) {
            PropertyDescriptor targetPd = var7[var9];
            Method writeMethod = targetPd.getWriteMethod();
            if (writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {
                PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());
                if (sourcePd != null) {
                    Method readMethod = sourcePd.getReadMethod();
                    if (readMethod != null && ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {
                        try {
                            if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {
                                readMethod.setAccessible(true);
                            }

                            Object value = readMethod.invoke(source);
                            if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
                                writeMethod.setAccessible(true);
                            }

                            writeMethod.invoke(target, value);
                        } catch (Throwable var15) {
                            throw new FatalBeanException("Could not copy property ‘" + targetPd.getName() + "‘ from source to target", var15);
                        }
                    }
                }
            }
        }

    }