A simple example of Java parsing annotations

The code is written according to the course Web tutorial.

Annotations for custom classes:

 Packagecom.immoc.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; @Target ({elementtype.type}) @Retention (retentionpolicy.runtime) @ Inherited@documented Public@InterfaceTable {String value ();}

Annotations for custom methods:

1  Packagecom.immoc.test;2 3 Importjava.lang.annotation.Documented;4 ImportJava.lang.annotation.ElementType;5 Importjava.lang.annotation.Inherited;6 Importjava.lang.annotation.Retention;7 ImportJava.lang.annotation.RetentionPolicy;8 ImportJava.lang.annotation.Target;9 Ten @Target ({Elementtype.field}) One @Retention (retentionpolicy.runtime) A @Inherited - @Documented -  Public@InterfaceColumn { the  - String value (); -}

Java class

 Packagecom.immoc.test; @Table ("User") Public classFilter {@Column ("id")    Private intID; @Column ("User_name")    PrivateString UserName; @Column ("Nick_name")    PrivateString Nickname; @Column ("Age")    Private intAge ; @Column ("City")    PrivateString City; @Column ("Mail")    PrivateString Mail; @Column ("Mobile")    PrivateString Mobile;  PublicString Getmobile () {returnMobile; }     Public voidSetmobile (String mobile) { This. Mobile =Mobile; }     PublicString Getmail () {returnMail; }     Public voidSetmail (String mail) { This. Mail =Mail; }     Public intgetId () {returnID; }     Public voidSetId (intID) { This. ID =ID; }     PublicString GetUserName () {returnUserName; }     Public voidsetusername (String userName) { This. UserName =UserName; }     PublicString Getnickname () {returnnickname; }     Public voidSetnickname (String nickname) { This. Nickname =nickname; }     Public intGetage () {returnAge ; }     Public voidSetage (intAge ) {         This. Age =Age ; }     PublicString getcity () {returnCity ; }     Public voidsetcity (String city) { This. City =City ; }    }

Test class

 Packagecom.immoc.test;ImportJava.lang.reflect.Field;ImportJava.lang.reflect.Method; Public classTest { Public Static voidMain (string[] args) {Filter F1=NewFilter (); F1.setid (10); Filter F2=NewFilter (); F2.setusername ("Tzzt01"); F2.setage (18); Filter f3=NewFilter (); F3.setmail ("[Email protected],[email protected]"); String SQL1=query (F1); String SQL2=query (F2); String Sql3=query (F3);        System.out.println (SQL1);        System.out.println (SQL2);    System.out.println (SQL3); }        Private StaticString query (Filter f) {StringBuilder SB=NewStringBuilder (); //1. Get the classClass C =F.getclass (); //2. Get the name of the table        Booleanexists = C.isannotationpresent (Table.class); if(!exists) {            return NULL; } Table T= (table) c.getannotation (table).class); String TableName=T.value (); Sb.append ("SELECT * from"). Append (TableName). Append ("Where 1=1"); //3. Iterate through all the fieldsfield[] Farray =C.getdeclaredfields ();  for(Field field:farray) {//4 working with each field's corresponding SQL//4.1 Get field name            BooleanFexists = Field.isannotationpresent (Column.class); if(!fexists) {                Continue; } Column Column= Field.getannotation (Column.class);//get Column.class's notesString columnName = Column.value ();//Get field name//4.2 Get the field valueString FieldName =Field.getname (); String Getmethodname= "Get" + fieldname.substring (0,1). toUpperCase () +fieldname.substring (1);//Get GetXXXObject Fieldvalue =NULL; Try{Method GetMethod=C.getmethod (getmethodname); Fieldvalue=Getmethod.invoke (f); } Catch(Exception e) {e.printstacktrace (); }            //4.3 assembling SQL            if(Fieldvalue = =NULL|| (FieldvalueinstanceofInteger && (integer) Fieldvalue = = 0)) {                Continue; } sb.append ("and"). Append (FieldName). Append ("="); if(FieldvalueinstanceofString) {                if((String) fieldvalue). Contains (",") {string[] values= (String) fieldvalue. Split (","); Sb.append ("In (");  for(String v:values) {sb.append ("'"). Append (v). Append ("'"). Append (","); } Sb.deletecharat (Sb.length ()-1); Sb.append (")"); } Else{sb.append ("'"). Append (Fieldvalue). Append ("'"); }            } Else if(FieldvalueinstanceofInteger)            {sb.append (fieldvalue); }        }        returnsb.tostring (); }}

A simple example of Java parsing annotations