Original Java uses reflection and custom annotations to achieve a comparison of object differences

There is a logic in Java Project C, where the resource data (type Resourceitem, with the int/double/boolean/string type of dozens of fields) needs to be different from each change in the resource data and describes the change. Not all fields need to be compared, such as ID fields do not participate in the alignment. It would be a heavy-duty job, in turn, to write code for each field. High-level languages give us a lot of convenience and should be used. First define your own annotations, value values are used as field descriptions

@Target (Elementtype.field) @Retention (retentionpolicy.runtime)  public @Interface  revisioncolumn {    String value ();}

Add the note for all Resourceitem fields, such as

 Public classResourceitem {Private intID; Private intrevision; Privateresourceitemstatus status; @RevisionColumn (Node)    PrivateString node; @RevisionColumn ("Physical Isolation")    Private Booleanphysicalisolation; @RevisionColumn ("Whole machine: single-disk maximum (%)")    Private intMachinedisklimit; //...}

Describes the entity type that first defines the difference in the Record object field before the comparison to logic

 Public classFieldchangeinfoImplementsserializable{PrivateString PropertyName; PrivateString Propertyheader; PrivateObject from; PrivateObject to;  PublicFieldchangeinfo () {} PublicFieldchangeinfo (String propertyname, String Propertyheader, object from, object to) { This. PropertyName =PropertyName;  This. Propertyheader =Propertyheader;  This. from =From ;  This. to =to ; } @Override Public Booleanequals (Object obj) {if(! (objinstanceoffieldchangeinfo)) return false; if(obj = = This)            return true; Fieldchangeinfo RHS=(fieldchangeinfo) obj; return NewEqualsbuilder ().                Append (PropertyName, Rhs.propertyname).                Append (Propertyheader, Rhs.propertyheader).                Append (from, Rhs.from).                Append (To, rhs.to).    Isequals (); }      PublicString Getpropertyname () {returnPropertyName; }      Public voidSetpropertyname (String PropertyName) { This. PropertyName =PropertyName; }      PublicString Getpropertyheader () {returnPropertyheader; }      Public voidSetpropertyheader (String propertyheader) { This. Propertyheader =Propertyheader; }      PublicObject Getfrom () {returnFrom ; }      Public voidSetfrom (Object from) { This. from =From ; }      PublicObject Getto () {returnto ; }      Public voidSetto (Object to) { This. to =to ; }}

FieldchangeinfoResource data Alignment logic, implement the following tool method 1, parameters accept Resourceitem old and new two objects 2, through reflection, Class.getdeclaredfields get the type of all fields 3, Call the Getannotation method of the field instance to get the Revisioncolumn annotation object, if it is not null, the field sets the annotation, makes a comparison of 4, gets the field value, detects a null reference, calls the Equals method to do a value match, and a mismatch occurs. Create Filedchangeinfo object record difference Information 5, return the Difference information collection

     Public StaticList<fieldchangeinfo>Getresourceitemfieldchangeinfo (Resourceitem originalitem, Resourceitem updateditem) {Try{List<FieldChangeInfo> Fieldchangeinfos =NewLinkedlist<>();  for(Field Field:resourceitem.class. Getdeclaredfields ()) {Revisioncolumn Revisioncolumn= Field.getannotation (revisioncolumn.class); if(Revisioncolumn! =NULL) {field.setaccessible (true); Object OriginalValue=Field.get (Originalitem); Object Updatedvalue=Field.get (Updateditem); if(OriginalValue = =NULL&& Updatedvalue = =NULL)                        Continue; if(OriginalValue = =NULL|| !originalvalue.equals (Updatedvalue)) {Fieldchangeinfo Fieldchangeinfo=NewFieldchangeinfo ();                        Fieldchangeinfo.setfrom (OriginalValue);                        Fieldchangeinfo.setto (Updatedvalue);                        Fieldchangeinfo.setpropertyname (Field.getname ());                        Fieldchangeinfo.setpropertyheader (Revisioncolumn.value ());                    Fieldchangeinfos.add (Fieldchangeinfo); }                }            }            returnFieldchangeinfos; } Catch(illegalaccessexception e) {Throw NewRuntimeException ("An exception occurred while detecting Resourceitem field changes"); }    }

GetresourceitemfieldchangeinfoIf necessary, you can convert a little refactoring to a generic method that supports the differential detection of which data types

Original Java uses reflection and custom annotations to achieve a comparison of object differences