Java自訂註解實現過程__java

步驟
1、建立自訂註解類，並添加校正規則
2、解析自訂註解類並實現校正方法
3、建立測試類別並聲明自訂註解
4、編寫Junit測試類別測試結果 自訂註解類

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;/** * 自訂註解類 * @author fuyuwei * @Retention: 定義註解的保留原則 * @Retention(RetentionPolicy.SOURCE)  註解僅存在於源碼中，在class位元組碼檔案中不包含   @Retention(RetentionPolicy.CLASS)   預設的保留原則，註解會在class位元組碼檔案中存在，但運行時無法獲得，   @Retention(RetentionPolicy.RUNTIME) 註解會在class位元組碼檔案中存在，在運行時可以通過反射擷取到   @Target 注釋型別宣告   CONSTRUCTOR 構造方法聲明   FIELD 欄位聲明（包括枚舉常量）   LOCAL_VARIABLE 局部變數聲明   METHOD 方法聲明   PACKAGE 包聲明   PARAMETER 參數聲明   TYPE 類、介面（包括注釋類型）或枚舉聲明 */@Retention(RetentionPolicy.RUNTIME)@Target({ElementType.TYPE,ElementType.FIELD,ElementType.PARAMETER})public @interface CustomAnnotation {    /**     * 是否為空白     * @return     */    boolean isNull() default false;    /**     * 最大長度     * @return     */    int maxLength() default 8;    /**     * 欄位描述     * @return     */    String description() default "";}

實現自訂註解類規則讀取與校正

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;/** * 解析自訂註解，並完成校正 * @author fuyuwei */public class AnnotationChecker {    private final static ConcurrentHashMap<String,Field[]> fieldsMap = new ConcurrentHashMap<String, Field[]>();    public AnnotationChecker(){        super();    }    public static void checkParam(Object object) throws PostingException{        Class<? extends Object> clazz = object.getClass();        Field[] fields = null;        if(fieldsMap.containsKey(clazz.getName())){            fields = fieldsMap.get(clazz.getName());        }        // getFields:獲得某個類的所有的公用（public）的欄位，包括父類;getDeclaredFields獲得某個類的所有申明的欄位，即包括public、private和proteced，但是不包括父類的申明欄位        else{            fields = clazz.getDeclaredFields();            fieldsMap.put(clazz.getName(), fields);        }        for(Field field:fields){            synchronized(field){                field.setAccessible(true);                check(field, object);                field.setAccessible(false);            }        }    }    private static void check(Field field,Object object) throws PostingException{        String description;        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;        // 如果沒有標註description預設展示欄位名稱        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(CommonPostCode.PARAM_LENGTH.getErrorCode(),description+" "+CommonPostCode.PARAM_LENGTH.getErrorCode());        }    }}

建立依賴的其他類 枚舉類

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;    }}

自訂異常類

package com.swk.common.exception;public class PostingException extends RuntimeException {    private static final long serialVersionUID = 5969404579580331293L;    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;    }}

建立聲明自訂註解的測試類別

package com.swk.request;import com.swk.common.annotation.CustomAnnotation;public class UserInfoRequest {    @CustomAnnotation(isNull=false,maxLength=4,description="姓名")    private String name;    @CustomAnnotation(isNull=false,maxLength=11,description="手機號")    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;    }}

編寫Junit測試類別

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());        }    }}

運行結果

@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("齊天大聖孫悟空");        try {            AnnotationChecker.checkParam(request);        } catch (PostingException e) {            logger.info(e.getErrorCode()+":"+e.getErrorMessage());        }    }}

運行結果