[原创]Java使用反射及自定义注解实现对象差异性比较

Java项目C中 有一处逻辑，对于资源数据（类型为ResourceItem，拥有int/double/boolean/String类型数十个字段），需要比对资源数据每次变更的差异，并描述出变更情况。并非所有的字段都需要比对，如id字段则不参与比对。

 

依次比对每一个字段编写代码比对，将是个重苦力活。高级语言给予了我们诸多便利，应当加以利用。

 

首先定义自己的注解，value值用作字段描述

@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
public @interface RevisionColumn {
    String value();
}

 

为ResourceItem所有待比对字段添加该注解，如

public class ResourceItem {
    private int id;
    private int revision;
    private ResourceItemStatus status;
 
    @RevisionColumn("节点")
    private String node;
 
    @RevisionColumn("是否物理隔离")
    private boolean physicalIsolation;
 
    @RevisionColumn("整机:单盘上限(%)")
    private int machineDiskLimit;
   
    //...
}

 

介绍比对逻辑前，首先定义记录对象字段差异的实体类型

public class FieldChangeInfo implements Serializable{
    private String propertyName;
    private String propertyHeader;
    private Object from;
    private Object to;
 
    public FieldChangeInfo() {
    }
 
    public FieldChangeInfo(String propertyName, String propertyHeader, Object from, Object to) {
        this.propertyName = propertyName;
        this.propertyHeader = propertyHeader;
        this.from = from;
        this.to = to;
    }
 
    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof FieldChangeInfo))
            return false;
        if (obj == this)
            return true;
 
        FieldChangeInfo rhs = (FieldChangeInfo) obj;
        return new EqualsBuilder().
                append(propertyName, rhs.propertyName).
                append(propertyHeader, rhs.propertyHeader).
                append(from, rhs.from).
                append(to, rhs.to).
                isEquals();
    }
 
    public String getPropertyName() {
        return propertyName;
    }
 
    public void setPropertyName(String propertyName) {
        this.propertyName = propertyName;
    }
 
    public String getPropertyHeader() {
        return propertyHeader;
    }
 
    public void setPropertyHeader(String propertyHeader) {
        this.propertyHeader = propertyHeader;
    }
 
    public Object getFrom() {
        return from;
    }
 
    public void setFrom(Object from) {
        this.from = from;
    }
 
    public Object getTo() {
        return to;
    }
 
    public void setTo(Object to) {
        this.to = to;
    }
}

FieldChangeInfo