Table of contents
A custom annotation
1. Meta-annotation
We need to add several meta-annotations to the custom annotations
@Target
@Retention
@Inherited
@Documented
1.1 Brief introduction
@Target
is used to declare where the current annotation can be used
| value | describe |
|---|---|
| ElementType.TYPE | Applies to classes, interfaces (including annotation types), and enumerations |
| ElementType.FIELD | Applies to properties (including constants in enumerations) |
| ElementType.METHOD | Apply to method |
| ElementType.PARAMETER | Formal parameters applied to methods |
| ElementType.CONSTRUCTOR | applied to constructor |
| ElementType.LOCAL_VARIABLE | applied to local variables |
| ElementType.ANNOTATION_TYPE | Applies to annotation types |
| ElementType.PACKAGE | applied to packages |
| ElementType.TYPE_PARAMETER | applied to type variables |
| ElementType.TYPE_USE | Applies to any statement that uses a type (such as types in declaration statements, generics, and cast statements) |
@Retention
indicates the life cycle of the annotation
| life cycle type | describe |
|---|---|
| RetentionPolicy.SOURCE | discarded at compile time and not included in the class file |
| RetentionPolicy.CLASS | Discarded when JVM loads, included in class file, default value |
| RetentionPolicy.RUNTIME | Loaded by the JVM, included in the class file, and can be obtained at runtime |
@Inherited
indicates that the annotation of the @Inherited annotation is used, and subclasses of the marked class will also have this annotation.
@Document
indicates that the element marked by this annotation can be documented by Javadoc or similar tools.
Generally, it is enough to use the first three when declaring custom annotations.
2 Statement annotation
// {} 中可以声明多个Target类型, 这个注解我们只用在类的属性上, 只注明这一个值即可
@Target({
ElementType.FIELD})
// 在运行时使用
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interface ExcelValid {
// 注解的属性
// 属性声明格式 : 数据类型 属性名() default 默认值;
// 在调用获取属性值的时候 直接通过 ' 注解对象.属性名()' 的形式
int length() default 0;
DataTypeEnum type() default DataTypeEnum.String;
boolean notNull() default true;
String lengthMessage() default "";
String typeMessage() default "";
String notNullMessage() default "";
}
enum class
public enum DataTypeEnum {
Byte("Byte"),
Short("Short"),
Integer("Integer"),
Long("Long"),
Float("Float"),
Double("Double"),
String("String"),
BigDecimal("BigDecimal"),
Boolean("Boolean");
private final String value;
private DataTypeEnum(String value) {
this.value = value;
}
public String value() {
return this.value;
}
This annotation is declared
2. Verification Tools
Write verification tool class
/**
* 导入excel参数校验
*/
public class ExcelValidUtil {
/**
* Excel导入字段校验
*
* @param object 校验的JavaBean 其属性须有自定义注解
*/
public static void Excelvalid(Object object) throws RuntimeException {
valid(object,0);
}
public static void Excelvalid(Object object, int size) throws RuntimeException {
valid(object,size);
}
private static void valid(Object object,int size) throws RuntimeException {
String prefix = "";
if (size > 0) {
prefix = "第" + size + "条数据";
}
// 通过反射获取类的所有属性字段
Field[] fields = object.getClass().getDeclaredFields();
for (Field field : fields) {
//设置可访问
field.setAccessible(true);
// 进行判断 如果属性上有 @ExcelIgnore 注解或者没有 @ExcelProperty则表示该字段不参数映射, 跳过
if (field.isAnnotationPresent(ExcelIgnore.class) || !field.isAnnotationPresent(ExcelProperty.class)) {
continue;
}
//属性的值
Object fieldValue = null;
try {
fieldValue = field.get(object);
} catch (IllegalAccessException e) {
throw new RuntimeException("导入参数检查失败");
}
//是否包含自定义校验注解
boolean hasValid = field.isAnnotationPresent(ExcelValid.class);
if (hasValid ) {
// 获取自定义注解
ExcelValid annotation = field.getAnnotation(ExcelValid.class);
// 非空校验
boolean notNull = annotation.notNull(); // 获取注解notNull属性的值
if (notNull && Objects.isNull(fieldValue)) {
throw new RuntimeException(prefix + " " +annotation.notNullMessage());
}
// 类型校验
DataTypeEnum type = annotation.type(); // 获取注解type属性的值
if (!validType(type,fieldValue)) {
throw new RuntimeException(prefix + " " +annotation.typeMessage());
}
// 长度校验
int length = annotation.length(); // 获取注解length属性的值
if (length > 0) {
if (length < String.valueOf(fieldValue).length()) {
throw new RuntimeException(prefix + " " +annotation.lengthMessage());
}
}
}
}
}
// 类型转换校验
private static Boolean validType(DataTypeEnum type,Object fieldValue) {
try {
switch (type){
case Byte: Byte.valueOf(String.valueOf(fieldValue)); break;
case Short: Short.valueOf(String.valueOf(fieldValue)); break;
case Integer: Integer.valueOf(String.valueOf(fieldValue)); break;
case Long: Long.valueOf(String.valueOf(fieldValue)); break;
case Float: Float.valueOf(String.valueOf(fieldValue)); break;
case Double: Double.valueOf(String.valueOf(fieldValue)); break;
case String: String.valueOf(fieldValue); break;
case BigDecimal: new BigDecimal(String.valueOf(fieldValue)); break;
case Boolean: Boolean.valueOf(String.valueOf(fieldValue)); break;
default: break;
}
}catch (Exception e){
// 转换失败返回false
return false;
}
return true;
}
}
3. Verification
3.1 Use custom annotations in excel templates
@Data
@ColumnWidth(25)
@HeadRowHeight(20)
@ContentRowHeight(18)
public class GoodsExcel implements Serializable {
private static final long serialVersionUID = 1L;
@ExcelProperty("租户编号（可空）")
@ExcelValid(length = 255,lengthMessage = "分类编号 过长",
notNull = false,
type = DataTypeEnum.String,typeMessage = "分类编号 数据格式异常")
private String tenantId;
// 其中notnull 默认值是 true, 可空字段要填成 false
// type 默认类型是string, 可省略不写
// 默认值信息可省略
@ExcelProperty("货品名称")
@ExcelValid(length = 255,lengthMessage = "货品名称 过长",
notNullMessage = "货品名称 不可为空"
)
private String goodsName;
// 没有 ExcelProperty 注解 不会校验该字段
@ColumnWidth(30)
@ExcelValid(length = 2,lengthMessage = "是否一物一码 过长",
notNullMessage = "是否一物一码 不可为空"
)
private String isNotEditStr;
// 有ExcelIgnore注解 不会校验该字段
@ExcelProperty("是否一物一码（是/否）")
@ExcelIgnore
private Integer isNotEdit;
}