找出两个用于版本跟踪的java bean之间的区别

问题描述

| 说我有一个Java bean /有100个字段的实体（是否继承，在这种情况下不相关）。更新操作后-在事务中，我想确定修改哪些字段以跟踪CVS之类的更新。最简单的方法是什么？有任何框架建议吗？我是否应该制作此对象的两个实例并遍历所有字段并匹配字段的值？在这种情况下最佳平等方法会如何出现？以下equals（）似乎很尴尬：

return (field1.equals(o.field1)) && 
(field2.equals(o.field2)) &&  
(field3.equals(o.field3)) &&  
...
(field100.equals(o.field100));

    

解决方法

您可以使用Apache Commons Beanutils。这是一个简单的示例：

package at.percom.temp.zztests;

import java.lang.reflect.InvocationTargetException;
import org.apache.commons.beanutils.BeanMap;
import org.apache.commons.beanutils.PropertyUtilsBean;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Objects;
import java.util.Set;

public class Main {

    public static void main(String[] args) throws IllegalAccessException,InvocationTargetException,NoSuchMethodException {
        Main main = new Main();
        main.start();
    }

    public void start() throws IllegalAccessException,NoSuchMethodException {
        SampleBean oldSample = new SampleBean(\"John\",\"Doe\",1971);
        SampleBean newSample = new SampleBean(\"John X.\",1971);

        SampleBean diffSample = (SampleBean) compareObjects(oldSample,newSample,new HashSet<>(Arrays.asList(\"lastName\")),10L);
    }

public Object compareObjects(Object oldObject,Object newObject,Set<String> propertyNamesToAvoid,Long deep) {
    return compareObjects(oldObject,newObject,propertyNamesToAvoid,deep,null);
}

private Object compareObjects(Object oldObject,Long deep,String parentPropertyPath) {
    propertyNamesToAvoid = propertyNamesToAvoid != null ? propertyNamesToAvoid : new HashSet<>();
    parentPropertyPath = parentPropertyPath != null ? parentPropertyPath : \"\";

    Object diffObject = null;
    try {
        diffObject = oldObject.getClass().newInstance();
    } catch (Exception e) {
        return diffObject;
    }

    BeanMap map = new BeanMap(oldObject);

    PropertyUtilsBean propUtils = new PropertyUtilsBean();

    for (Object propNameObject : map.keySet()) {
        String propertyName = (String) propNameObject;
        String propertyPath = parentPropertyPath + propertyName;

        if (!propUtils.isWriteable(diffObject,propertyName) || !propUtils.isReadable(newObject,propertyName)
                || propertyNamesToAvoid.contains(propertyPath)) {
            continue;
        }

        Object property1 = null;
        try {
            property1 = propUtils.getProperty(oldObject,propertyName);
        } catch (Exception e) {
        }
        Object property2 = null;
        try {
            property2 = propUtils.getProperty(newObject,propertyName);
        } catch (Exception e) {
        }
        try {
            if (property1 != null && property2 != null && property1.getClass().getName().startsWith(\"com.racing.company\")
                    && (deep == null || deep > 0)) {
                Object diffProperty = compareObjects(property1,property2,deep != null ? deep - 1 : null,propertyPath + \".\");
                propUtils.setProperty(diffObject,propertyName,diffProperty);
            } else {
                if (!Objects.deepEquals(property1,property2)) {
                    propUtils.setProperty(diffObject,property2);
                    System.out.println(\"> \" + propertyPath + \" is different (oldValue=\\\"\" + property1 + \"\\\",newValue=\\\"\"
                            + property2 + \"\\\")\");
                } else {
                    System.out.println(\"  \" + propertyPath + \" is equal\");
                }
            }
        } catch (Exception e) {
        }
    }

    return diffObject;
}

    public class SampleBean {

        public String firstName;
        public String lastName;
        public int yearOfBirth;

        public SampleBean(String firstName,String lastName,int yearOfBirth) {
            this.firstName = firstName;
            this.lastName = lastName;
            this.yearOfBirth = yearOfBirth;
        }

        public String getFirstName() {
            return firstName;
        }

        public String getLastName() {
            return lastName;
        }

        public int getYearOfBirth() {
            return yearOfBirth;
        }
    }
}

    ,嘿，看看Javers正是您所需要的-对象审核和diff框架。使用Javers，您可以在每次更新后通过一次

javers.commit()

调用来保留对域对象所做的更改。当您坚持进行某些更改时，可以按

javers.getChangeHistory

轻松读取它们，例如

public static void main(String... args) {
    //get Javers instance
    Javers javers = JaversBuilder.javers().build();

    //create java bean
    User user = new User(1,\"John\");

    //commit current state
    javers.commit(\"author\",user);

    //update operation
    user.setUserName(\"David\");

    //commit change
    javers.commit(\"author\",user);

    //read 100 last changes
    List<Change> changes = javers.getChangeHistory(instanceId(1,User.class),100);

    //print change log
    System.out.printf(javers.processChangeList(changes,new SimpleTextChangeLog()));
}

输出为：

commit 2.0,author:author,2015-01-07 23:00:10
  changed object: org.javers.demo.User/1
    value changed on \'userName\' property: \'John\' -> \'David\'
commit 1.0,2015-01-07 23:00:10
    new object: \'org.javers.demo.User/1

    ,您可以使用反射来加载字段，然后在每个对象上调用它们并比较结果。 示例源代码可能如下所示：

public static <T> void Compare(T source,T target) throws IllegalArgumentException,IllegalAccessException {

            if(source == null) {
                throw new IllegalArgumentException(\"Null argument not excepted at this point\");
            }

            Field[] fields = source.getClass().getFields();

            Object sourceObject;
            Object targetObject;

            for(Field field : fields){
                sourceObject = field.get(source);
                targetObject = field.get(target);

                //Compare the object

            }

        }

仅供参考，此代码仅适用于为类声明的公共字段。     ,您可以使用Apache BeanUtils检出属性。