Annotation的大材小用

最近在開發一些通用的excel數據導入的功能，因爲涉及到導入的模塊不少，因此開發了一個比較通用的excel導入模板類文件。而且使用annotation做爲驗證數據的配置。

package com.hp.dylan.jv;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface ExcelAnnotation {
	
//excel column name
	public String importCellName();

//excel cell data weather is required
	public boolean isRequired();

//excel cell data datalength.	
	public int importDataLen();

//excel cell data type.	
	public String importDataType();
	
//excel cell mapping index.
	public int importCellIndex();

//excel data weather eixts in db.	
	public boolean isEixtance();
}

看看須要導入excel的模型類的定義：(AdditionJvImportModel)

package com.hp.dylan.jv;
public class AdditionJvImportModel {
 @ExcelAnnotation( importCellName = "EN1",isRequired=true ,importDataLen=100,importDataType="String",importCellIndex = 1,isEixtance=true)
 private String sellEntity;
 @ExcelAnnotation(importCellName = "SE2",isRequired=false ,importDataLen=4,importDataType="String",importCellIndex =2, isEixtance=false)
 private String sellSe;
 @ExcelAnnotation(importCellName = "DI3",isRequired=false ,importDataLen=10,importDataType="String",importCellIndex = 3, isEixtance=false)
 private String sellDi;
 @ExcelAnnotation(importCellName = "DEPT4",isRequired=false ,importDataLen=8,importDataType="String",importCellIndex = 4, isEixtance=false)
 private String sellDept;
 @ExcelAnnotation(importCellName = "SF5",isRequired=false ,importDataLen=10,importDataType="String",importCellIndex = 5, isEixtance=false)
 private String sellSf;
 @ExcelAnnotation(importCellName = "PT6",isRequired=false ,importDataLen=4,importDataType="String",importCellIndex = 6, isEixtance=false)
 private String sellPt;
 @ExcelAnnotation(importCellName = "PL7",isRequired=false ,importDataLen=10,importDataType="String",importCellIndex = 7, isEixtance=false)
 private String sellPl;
 @ExcelAnnotation(importCellName = "SL8",isRequired=false ,importDataLen=4,importDataType="String",importCellIndex = 8, isEixtance=false)
 private String sellSl;
 @ExcelAnnotation(importCellName = "Amount9",isRequired=false ,importDataLen=25,importDataType="number(25,10)",importCellIndex = 9, isEixtance=false)
 private String sellAmout;
 @ExcelAnnotation(importCellName = "EN10",isRequired=true ,importDataLen=100,importDataType="String",importCellIndex = 10, isEixtance=true)
 private String buyEntity;
 @ExcelAnnotation(importCellName = "SE11",isRequired=false ,importDataLen=4,importDataType="String",importCellIndex = 11, isEixtance=false)
 private String buySe;
 @ExcelAnnotation(importCellName = "DI12",isRequired=false ,importDataLen=10,importDataType="String",importCellIndex = 12, isEixtance=false)
 private String buyDi;
 @ExcelAnnotation(importCellName = "DEPT13",isRequired=false ,importDataLen=8,importDataType="String",importCellIndex = 13, isEixtance=false)
 private String buyDept;
 @ExcelAnnotation(importCellName = "SF14",isRequired=false ,importDataLen=10,importDataType="String",importCellIndex = 14, isEixtance=false)
 private String buySf;
 @ExcelAnnotation(importCellName = "PT15",isRequired=false ,importDataLen=4,importDataType="String",importCellIndex = 15, isEixtance=false)
 private String buyPt;
 @ExcelAnnotation(importCellName = "PL16",isRequired=false ,importDataLen=10,importDataType="String",importCellIndex = 16, isEixtance=false)
 private String buyPl;
 @ExcelAnnotation(importCellName = "SL17",isRequired=false ,importDataLen=4,importDataType="String",importCellIndex = 17, isEixtance=false)
 private String buySl;
 @ExcelAnnotation(importCellName = "LSA Factor19",isRequired=false ,importDataLen=25,importDataType="number(25,10)",importCellIndex = 19, isEixtance=false)
 private String tranFactor;
 @ExcelAnnotation(importCellName = "GrossICPurchase20",isRequired=false ,importDataLen=25,importDataType="number(25,10)",importCellIndex = 20, isEixtance=false)
 private String tranGross;
 @ExcelAnnotation(importCellName = "EX Code21",isRequired=false ,importDataLen=5,importDataType="String",importCellIndex = 21, isEixtance=false)
 private String tranExCode;
 @ExcelAnnotation(importCellName = "Transaction Description24",isRequired=false ,importDataLen=200,importDataType="String",importCellIndex = 24, isEixtance=false)
 private String tranDesr;
 @ExcelAnnotation(importCellName = "Line Comments25",isRequired=false ,importDataLen=200,importDataType="String",importCellIndex = 25, isEixtance=false)
 private String tranLineComm;
 @ExcelAnnotation(importCellName = "Additional Line Comments30",isRequired=false ,importDataLen=200,importDataType="String",importCellIndex = 30, isEixtance=false)
 private String tranAddLinComm;
 @ExcelAnnotation(importCellName = "FROM VATID31",isRequired=false ,importDataLen=6,importDataType="String",importCellIndex = 31, isEixtance=false)
 private String tranFVatId;
 @ExcelAnnotation(importCellName = "TO VATID32",isRequired=false ,importDataLen=6,importDataType="String",importCellIndex = 32, isEixtance=false)
 private String tranTVatId;
}

excel模型的解析中如何獲取到此模型的描述配置。也就是獲取他的annotation。

Map<Integer,ExcelAnnotation> mapping=new HashMap<Integer,ExcelAnnotation>();
   for (int i = 0; i < filed.length; i++) {
    Field f = filed[i];
    ExcelAnnotation excel = f.getAnnotation(ExcelAnnotation.class);
    if (excel != null) {
     mapping.put(excel.importCellIndex(), excel);
    }
   }

如何根據annotation的描述來驗證。

if(anno.isRequired()){
       if(cellValue==null||"".equals(cellValue.trim())){
            sb.append(anno.importCellName()+" can not be empty!"); 。。。}
     }

若是須要跟db交互來進行檢驗的話，只須要定義一個abstract校驗方法，具體的校驗規則交給其實現者來完成

public abstract String validateExist(String value);

Noted:

你能夠annotation徹底的看作一種配置，你只須要獲取你的model種的annotation標識，而後根據標識來進行一個校驗規則的解析

你也能夠結合 class reflection 機制來使用annotation，獲取到model的annotation描述以後，根據class reflection 來動態的激活調用一些model中的方法，