以下代码有什么问题:public void tableAnnotationJSQ(Class<?> clazz,Annotation annotation){ Field[] fields=clazz.getDeclaredFields(); for(Field field:fields){ AiAnnotation aiAnnotation = field.getAnnotation(annotation.getClass()); field.setAccessible(true); try { field.set(this, aiAnnotation.value()); } catch (IllegalAccessException e) { e.printStackTrace(); } } }
时间: 2023-06-04 22:03:28 浏览: 49
抱歉,我可以回答这个问题。这个代码中可能会出现空指针异常,因为没有对 field.getAnnotation(annotation.getClass()) 的返回结果进行判空处理。如果 aiAnnotation 为 null,调用 aiAnnotation.value() 会抛出空指针异常。可能需要添加一个非空判断。
相关问题
我要你扮演一个软件工程师。现在我需要你仔细思考,以下代码存在一些问题,headClazz传入空值,我想要headClazz能获取到entity包中的user、admin表的实体类,我需要你指出代码错误,以及改正方法。代码如下:private Class<?> headClazz;/** * @param headClazz excel model 类对象 */ public CommonReadListener(Class<?> headClazz) { this.headClazz = headClazz; }@Override public void invokeHead(Map<Integer, ReadCellData<?>> headMap, AnalysisContext context) { ExcelPropertyCheck clazzHeadAnno = this.headClazz.getAnnotation(ExcelPropertyCheck.class); Field[] declaredFields = headClazz.getDeclaredFields(); if (clazzHeadAnno != null && clazzHeadAnno.required()) { for (Field declaredField : declaredFields) { nullAbleFieldMap.put(declaredField.getName(), true); } } for (Field declaredField : declaredFields) { ExcelPropertyCheck annotation = declaredField.getAnnotation(ExcelPropertyCheck.class); if (annotation != null) { if (annotation.checkFormat()) { checkFormatFieldMap.put(declaredField.getName(), annotation.type() + ""); } if (annotation.required()) { nullAbleFieldMap.put(declaredField.getName(), true); } else { nullAbleFieldMap.remove(declaredField.getName()); } if (annotation.required() && annotation.length() != -1) { checkLengthFieldMap.put(declaredField.getName(), annotation.length()); } } } }
问题代码在于headClazz传入空值时,会导致NullPointerException异常。为了让headClazz获取到entity包中的user、admin表的实体类,你需要修改代码如下:
1.首先,你需要判断headClazz是否为空,如果为空则抛出IllegalArgumentException异常,代码如下:
```
public CommonReadListener(Class<?> headClazz) {
if (headClazz == null) {
throw new IllegalArgumentException("headClazz不能为null");
}
this.headClazz = headClazz;
}
```
2.其次,你需要使用Class.forName()方法获取实体类的Class对象,然后将其传入CommonReadListener构造方法中。代码如下:
```
Class<?> userClazz = Class.forName("com.example.entity.User");
Class<?> adminClazz = Class.forName("com.example.entity.Admin");
List<Class<?>> clazzList = new ArrayList<>();
clazzList.add(userClazz);
clazzList.add(adminClazz);
CommonReadListener commonReadListener = new CommonReadListener(clazzList);
```
3.最后,在CommonReadListener类中,你需要修改invokeHead方法的实现,以支持多个实体类的字段校验。代码如下:
```
@Override
public void invokeHead(Map<Integer, ReadCellData<?>> headMap, AnalysisContext context) {
ExcelPropertyCheck clazzHeadAnno = this.headClazz.getAnnotation(ExcelPropertyCheck.class);
Field[] declaredFields = new Field[0];
for (Class<?> clazz : clazzList) {
declaredFields = ArrayUtils.addAll(declaredFields, clazz.getDeclaredFields());
}
if (clazzHeadAnno != null && clazzHeadAnno.required()) {
for (Field declaredField : declaredFields) {
nullAbleFieldMap.put(declaredField.getName(), true);
}
}
for (Field declaredField : declaredFields) {
ExcelPropertyCheck annotation = declaredField.getAnnotation(ExcelPropertyCheck.class);
if (annotation != null) {
if (annotation.checkFormat()) {
checkFormatFieldMap.put(declaredField.getName(), annotation.type() + "");
}
if (annotation.required()) {
nullAbleFieldMap.put(declaredField.getName(), true);
} else {
nullAbleFieldMap.remove(declaredField.getName());
}
if (annotation.required() && annotation.length() != -1) {
checkLengthFieldMap.put(declaredField.getName(), annotation.length());
}
}
}
}
```
以上是修改后的代码,可以让headClazz获取到entity包中的user、admin表的实体类。
我要你扮演一个软件工程师。现在我需要你仔细思考,以下代码存在一些问题,headClazz里面获取到的是空值,我想要headClazz能动态获取到entity包中的user、admin表,我需要你指出代码错误,以及改正方法。代码如下:public class CommonReadListener<T> extends AnalysisEventListener<T> implements ReadListener<T> {private Class<T> headClazz;public CommonReadListener(Class<T> headClazz) { this.headClazz = headClazz; }@Override public void invokeHead(Map<Integer, ReadCellData<?>> headMap, AnalysisContext context) { ExcelPropertyCheck clazzHeadAnno = this.headClazz.getAnnotation(ExcelPropertyCheck.class); Field[] declaredFields = headClazz.getDeclaredFields(); if (clazzHeadAnno != null && clazzHeadAnno.required()) { for (Field declaredField : declaredFields) { nullAbleFieldMap.put(declaredField.getName(), true); } } for (Field declaredField : declaredFields) { ExcelPropertyCheck annotation = declaredField.getAnnotation(ExcelPropertyCheck.class); if (annotation != null) { if (annotation.checkFormat()) { checkFormatFieldMap.put(declaredField.getName(), annotation.type() + ""); } if (annotation.required()) { nullAbleFieldMap.put(declaredField.getName(), true); } else { nullAbleFieldMap.remove(declaredField.getName()); } if (annotation.required() && annotation.length() != -1) { checkLengthFieldMap.put(declaredField.getName(), annotation.length()); } } } }
这段代码中,headClazz是一个类类型参数,它通过构造方法传入,但是在代码中没有看到headClazz的值在哪里被设置。所以,获取到的headClazz为null。
要让headClazz能够动态获取到entity包中的user、admin表,可以使用Java反射机制来实现。可以添加一个参数tableName,用来指定表名,然后通过反射获取指定表名对应的类,最后将获取的类作为headClazz的值。
修改后的代码如下:
```
public class CommonReadListener<T> extends AnalysisEventListener<T> implements ReadListener<T> {
private Class<T> headClazz;
public CommonReadListener(Class<T> headClazz) {
this.headClazz = headClazz;
}
public CommonReadListener(String tableName) {
try {
String className = "entity." + tableName;
Class<T> clazz = (Class<T>) Class.forName(className);
this.headClazz = clazz;
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
@Override
public void invokeHead(Map<Integer, ReadCellData<?>> headMap, AnalysisContext context) {
ExcelPropertyCheck clazzHeadAnno = this.headClazz.getAnnotation(ExcelPropertyCheck.class);
Field[] declaredFields = headClazz.getDeclaredFields();
if (clazzHeadAnno != null && clazzHeadAnno.required()) {
for (Field declaredField : declaredFields) {
nullAbleFieldMap.put(declaredField.getName(), true);
}
}
for (Field declaredField : declaredFields) {
ExcelPropertyCheck annotation = declaredField.getAnnotation(ExcelPropertyCheck.class);
if (annotation != null) {
if (annotation.checkFormat()) {
checkFormatFieldMap.put(declaredField.getName(), annotation.type() + "");
}
if (annotation.required()) {
nullAbleFieldMap.put(declaredField.getName(), true);
} else {
nullAbleFieldMap.remove(declaredField.getName());
}
if (annotation.required() && annotation.length() != -1) {
checkLengthFieldMap.put(declaredField.getName(), annotation.length());
}
}
}
}
}
```
使用方法:
```
CommonReadListener<User> userListener = new CommonReadListener<>("user");
CommonReadListener<Admin> adminListener = new CommonReadListener<>("admin");
```