Annotations (ii) mapping of simulated entities to database table fields

 Packagecom.ann.test;Importjava.lang.annotation.Documented;ImportJava.lang.annotation.ElementType;Importjava.lang.annotation.Inherited;Importjava.lang.annotation.Retention;ImportJava.lang.annotation.RetentionPolicy;ImportJava.lang.annotation.Target;/*** Field Custom annotations*/@Target ({Elementtype.field}) @Retention (retentionpolicy.runtime) @Inherited @documented Public@InterfaceColumn {String value ();}

 Packagecom.ann.test;Importjava.lang.annotation.Documented;ImportJava.lang.annotation.ElementType;Importjava.lang.annotation.Inherited;Importjava.lang.annotation.Retention;ImportJava.lang.annotation.RetentionPolicy;ImportJava.lang.annotation.Target;/*** Table Custom annotations*/@Target ({elementtype.type}) @Retention (retentionpolicy.runtime) @Inherited @documented Public@InterfaceTable {String value ();}

 Packagecom.ann.test;/*** User entity usage Annotations*/@Table ("User") Public classUser {@Column ("id")    Private intID; @Column ("UserName")    PrivateString UserName; @Column ("Sex")    Private intsex; @Column ("Mobile")    PrivateString Mobile;  Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetUserName () {returnUserName; }     Public voidsetusername (String userName) { This. UserName =UserName; }     Public intGetsex () {returnsex; }     Public voidSetsex (intsex) {         This. Sex =sex; }     PublicString Getmobile () {returnMobile; }     Public voidSetmobile (String mobile) { This. Mobile =Mobile; }    }

 Packagecom.ann.test;ImportJava.lang.reflect.Field;ImportJava.lang.reflect.Method;/*** test of simulating Entity to database table field*/ Public classTest { Public Static voidMain (string[] args) {User u=NewUser (); U.setusername ("Zhang San"); U.setsex (1);    System.out.println (Parseuser (U)); }         Public StaticString Parseuser (User u) {stringbuffer sb=NewStringBuffer (); Sb.append ("SELECT * from"); Try {            //1.1 Load class with class loader, get table nameClass C = class.forname ("Com.ann.test.User"); //1.2 Find the annotations on the class and get the annotation instance            if(C.isannotationpresent (Table.class) ) {Table T= (table) c.getannotation (table).class); String TableName=T.value ();            Sb.append (TableName); } sb.append ("Where 1=1"); //2. Get field names and valuesfield[] fs =C.getdeclaredfields ();  for(Field f:fs) {//2.1 Field namesString column = ""; if(F.isannotationpresent (Column).class) {Column fld= (column) f.getannotation (column).class); Column=Fld.value (); }                //2.2 field ValueString FieldName =F.getname (); String GetMethod= "Get" +fieldname.substring (0, 1). toUpperCase () +fieldname.substring (1); Method Method=C.getmethod (GetMethod); Object Fieldvalue=method.invoke (U); if(FieldvalueinstanceofInteger && (integer) Fieldvalue = = 0){                    Continue; }                if(Fieldvalue! =NULL) {sb.append ("and"). Append (column). Append ("="); if(FieldvalueinstanceofString) {Sb.append ("'"). Append (Fieldvalue). Append ("'"); }Else{sb.append (fieldvalue); }                }            }                    } Catch(Exception e) {e.printstacktrace (); }        returnsb.tostring (); }}

Output Result:

SELECT * from user where 1=1 and Username= ' Zhang San ' and Sex=1

Annotations (ii) mapping of simulated entities to database table fields