Java Custom annotation Implementation process __java

Step
1, create a custom annotation class, add a checksum rule
2, parse a custom annotation class and implement a validation method
3, create a test class and declare a custom note
4, write a JUnit test class test Results custom annotation Class

Package com.swk.common.annotation;
Import Java.lang.annotation.ElementType;
Import java.lang.annotation.Retention;
Import Java.lang.annotation.RetentionPolicy;

Import Java.lang.annotation.Target; 
   /** * Custom Annotation class * @author Fuyuwei * @Retention: A retention policy that defines annotations * @Retention (retentionpolicy.source) annotations exist only in the source code and are not included in the class byte code file @Retention (retentionpolicy.class) default retention policy, annotations are present in the CLASS bytecode file but not available at run time, @Retention (retentionpolicy.runtime) annotations will be found in the CLA  SS bytecode file, which can be obtained by reflection to @Target annotation type declaration constructor constructor declaration FIELD field declaration (including enumeration constants) Local_variable local variable declaration method Method declaration PACKAGE Package declaration PARAMETER parameter declaration type class, interface (including annotation type) or enum declaration/@Retention (Retentionpolicy.runtime) @Target ({Elementt Ype.
     Type,elementtype.field,elementtype.parameter}) Public @interface customannotation {/** * is empty * @return

    * * Boolean isNull () default false;

    /** * Maximum length * @return/int maxLength () default 8; /** * Field Description * @return/String description () deFault ""; }

Implement custom annotation class rules read and verify

Package com.swk.common.annotation;
Import Java.lang.reflect.Field;

Import Java.util.concurrent.ConcurrentHashMap;

Import Org.springframework.util.StringUtils;
Import Com.swk.common.enums.CommonPostCode;


Import com.swk.common.exception.PostingException; /** * resolves the custom annotation and completes the checksum * @author Fuyuwei/public class Annotationchecker {private final static CONCURRENTHASHMAP&L T

    string,field[]> Fieldsmap = new concurrenthashmap<string, field[]> ();
    Public Annotationchecker () {super ();  public static void Checkparam (Object object) throws postingexception{class<? extends object> =
        Object.getclass ();
        field[] fields = NULL;
        if (Fieldsmap.containskey (Clazz.getname ())) {fields = Fieldsmap.get (Clazz.getname ()); }//GetFields: Gets all public fields of a class, including the parent class, and Getdeclaredfields obtains all the declared fields of a class, that is, the general, private, and proteced.
            But not including the parent class's declaration field else{fields = Clazz.getdeclaredfields (); FieLdsmap.put (Clazz.getname (), fields);
                for (field Field:fields) {synchronized (field) {field.setaccessible (true);
                Check (field, object);
            Field.setaccessible (FALSE); The private static void check (Field field,object Object) throws postingexception{String Descri
        ption;
        Object value = null;
        Customannotation CA = field.getannotation (customannotation.class);
        try {value = Field.get (object);
        catch (IllegalArgumentException e) {e.printstacktrace ();
        catch (Illegalaccessexception e) {e.printstacktrace ();
        } if (ca = = null) return;
        If there is no callout description The default display field name Description = Ca.description (). Equals ("")? Field.getname (): Ca.description (); if (!ca.isnull ()) {if (value = NULL | | Stringutils.isempty (value.tostring (). Trim ())) {throw new Postingexception (CommonPostCode.PARAM_LENGTH.getErrorCode (), description+ "" +commonpostcode.param_null.geterrormesage ()); } if (Value.tostring (). Length () > Ca.maxlength ()) {throw new Postingexception (Commonpostco De.
        Param_length.geterrorcode (), description+ "" +commonpostcode.param_length.geterrorcode ()); }
    }
}

to create a dependent other class Enumeration Class

Package com.swk.common.enums;

public enum Commonpostcode {

    param_null ( -1, "PARAM required"),
    param_length ( -2, "PARAM too Long");

    private int errorcode;

    Private String errormesage;


    Private Commonpostcode (int errorcode, String errormesage) {
        this.errorcode = errorcode;
        This.errormesage = Errormesage;
    }

    public int GetErrorCode () {return
        errorcode;
    }

    public void Seterrorcode (int errorcode) {
        this.errorcode = errorcode;
    }

    Public String Geterrormesage () {return
        errormesage;
    }

    public void Seterrormesage (String errormesage) {
        this.errormesage = errormesage;
    }


}

Custom Exception Classes

Package com.swk.common.exception;

public class Postingexception extends RuntimeException {

    private static final long Serialversionuid = 596940457958033 1293L;

    private int errorcode;

    Private String errormessage;

    Public postingexception (int errorcode, String errormessage) {
        super ();
        This.errorcode = errorcode;
        This.errormessage = errormessage;
    }

    public int GetErrorCode () {return
        errorcode;
    }

    public void Seterrorcode (int errorcode) {
        this.errorcode = errorcode;
    }

    Public String GetErrorMessage () {return
        errormessage;
    }

    public void Seterrormessage (String errormessage) {
        this.errormessage = errormessage;
    }



}

to create a test class that declares custom annotations

Package com.swk.request;

Import com.swk.common.annotation.CustomAnnotation;

public class Userinforequest {

    @CustomAnnotation (isnull=false,maxlength=4,description= "name")
    private String Name;

    @CustomAnnotation (isnull=false,maxlength=11,description= "mobile phone number")
    private String mobile;

    Public String GetName () {return
        name;
    }

    public void SetName (String name) {
        this.name = name;
    }

    Public String Getmobile () {return
        mobile;
    }

    public void Setmobile (String mobile) {
        this.mobile = mobile;
    }


}

writing JUnit test classes

Package com.swk.test.annotation;

Import Org.junit.Test;
Import Org.junit.runner.RunWith;
Import org.springframework.test.context.ContextConfiguration;
Import Org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

Import Com.sun.istack.internal.logging.Logger;
Import Com.swk.common.annotation.AnnotationChecker;
Import com.swk.common.exception.PostingException;
Import Com.swk.request.UserInfoRequest;

@RunWith (Springjunit4classrunner.class)
@ContextConfiguration (locations = {"Classpath:spring-mybatis.xml"}) Public
class Annotationtest {

    private Logger Logger = Logger.getlogger (annotationtest.class);

    @Test public
    void Testannotation () {
        userinforequest request = new Userinforequest ();
        try {
            Annotationchecker.checkparam (request);
        } catch (Postingexception e) {
            logger.info ( E.geterrorcode () + ":" +e.geterrormessage ());}}}

Run results

@RunWith (Springjunit4classrunner.class)
@ContextConfiguration (locations = {"Classpath:spring-mybatis.xml"}) Public
class Annotationtest {

    private Logger Logger = Logger.getlogger (annotationtest.class);

    @Test public
    void Testannotation () {
        userinforequest request = new Userinforequest ();
        Request.setname ("Qi Tian San Sun wukong");
        try {
            Annotationchecker.checkparam (request);
        } catch (Postingexception e) {
            logger.info (e.geterrorcode () + ":" +e.geterrormessage ());}}}

Run results