Java对象空指针校验工具类
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简介
对象空指针是指一个指针变量指向了内存中的空地址，也就是没有指向任何有效对象的地址。在许多编程语言中，空指针通常用特殊的值（例如NULL、nil、None等）表示。
当你使用一个空指针来访问对象的成员或调用对象的方法时，会导致空指针异常（Null Pointer Exception）或类似的错误。这是因为空指针并没有指向有效的对象，无法执行相应的操作。
空指针错误通常是由以下几种情况引起的：
- 未初始化指针：当你声明一个指针变量但没有给它赋予有效的地址时，它的值就是空指针。如果你在使用该指针之前没有对其进行初始化，就会导致空指针异常。
- 对象释放或销毁：如果你在释放或销毁一个对象后，仍然使用指向该对象的指针，就会得到空指针异常。这通常发生在动态内存分配的情况下，例如使用new关键字创建的对象。
- 对象不存在：当你试图访问一个不存在的对象或已经被销毁的对象时，指向该对象的指针就会成为空指针。这可能是由于对象在之前的代码中未被正确创建或意外地被销毁。
为了避免空指针错误，你可以在使用指针之前进行有效性检查，或者使用安全的编程技术，如空指针检查、异常处理等。
工具类
1 基于若依改动
1.1 调用示例
/**
* 根据id查询文章列表
*
* @param article 文章
* @return 文章
*/
@Override
public Article getArticleById(Long id)
{
Article article = baseMapper.selectArticleById(id);
AssertUtils.isNotEmpty(article,"抛出异常");
return article;
}
AssertUtil：校验工具类
package com.torinosrc.common.utils.star;
import cn.hutool.core.util.ObjectUtil;
import com.torinosrc.common.exception.ServiceException;
import java.text.MessageFormat;
import java.util.Objects;
/**
* 校验工具类
*/
public class AssertUtil {
//如果不是true，则抛异常
public static void isTrue(boolean expression, String msg) {
if (!expression) {
throwException(msg);
}
}
public static void isTrue(boolean expression, ErrorEnum errorEnum, Object... args) {
if (!expression) {
throwException(errorEnum, args);
}
}
//如果是true，则抛异常
public static void isFalse(boolean expression, String msg) {
if (expression) {
throwException(msg);
}
}
//如果是true，则抛异常
public static void isFalse(boolean expression, ErrorEnum errorEnum, Object... args) {
if (expression) {
throwException(errorEnum, args);
}
}
//如果不是非空对象，则抛异常
public static void isNotEmpty(Object obj, String msg) {
if (isEmpty(obj)) {
throwException(msg);
}
}
//如果不是非空对象，则抛异常
public static void isNotEmpty(Object obj, ErrorEnum errorEnum, Object... args) {
if (isEmpty(obj)) {
throwException(errorEnum, args);
}
}
//如果不是非空对象，则抛异常
public static void isEmpty(Object obj, String msg) {
if (!isEmpty(obj)) {
throwException(msg);
}
}
public static void equal(Object o1, Object o2, String msg) {
if (!ObjectUtil.equal(o1, o2)) {
throwException(msg);
}
}
public static void notEqual(Object o1, Object o2, String msg) {
if (ObjectUtil.equal(o1, o2)) {
throwException(msg);
}
}
private static boolean isEmpty(Object obj) {
return ObjectUtil.isEmpty(obj);
}
private static void throwException(String msg) {
throwException(null, msg);
}
private static void throwException(ErrorEnum errorEnum, Object... arg) {
if (Objects.isNull(errorEnum)) {
errorEnum = BusinessErrorEnum.BUSINESS_ERROR;
}
throw new ServiceException(errorEnum.getErrorCode(), MessageFormat.format(errorEnum.getErrorMsg(), arg));
}
}
1.2 BusinessErrorEnum：业务校验异常码
package com.torinosrc.common.utils.star;
/**
* Description: 业务校验异常码
*/
public enum BusinessErrorEnum implements ErrorEnum {
//==================================common==================================
BUSINESS_ERROR(1001, "{0}"),
//==================================chat==================================
SYSTEM_ERROR(1001, "系统出小差了，请稍后再试哦~~"),
;
private Integer code;
private String msg;
BusinessErrorEnum(Integer code, String msg) {
this.code = code;
this.msg = msg;
}
@Override
public Integer getErrorCode() {
return code;
}
@Override
public String getErrorMsg() {
return msg;
}
public Integer getCode() {
return code;
}
public BusinessErrorEnum setCode(Integer code) {
this.code = code;
return this;
}
public String getMsg() {
return msg;
}
public BusinessErrorEnum setMsg(String msg) {
this.msg = msg;
return this;
}
}
1.3 ServiceException：修改若依业务异常
package com.torinosrc.common.exception;
/**
* 业务异常
*
* @author ruoyi
*/
public final class ServiceException extends RuntimeException
{
private static final long serialVersionUID = 1L;
/**
* 错误码
*/
private Integer code;
/**
* 错误提示
*/
private String message;
/**
* 错误明细，内部调试错误
*
* 和 {@link CommonResult#getDetailMessage()} 一致的设计
*/
private String detailMessage;
/**
* 空构造方法，避免反序列化问题
*/
public ServiceException()
{
}
public ServiceException(String message) {
this.message = message;
}
public ServiceException(String message, Integer code) {
this.message = message;
this.code = code;
}
// 增加方法1
public ServiceException(Integer errorCode, String errorMsg) {
super(errorMsg);
this.code = errorCode;
this.message = errorMsg;
}
// 增加方法2
public ServiceException(Integer errorCode, String errorMsg, Throwable cause) {
super(errorMsg, cause);
this.code = errorCode;
this.message = errorMsg;
}
public String getDetailMessage() {
return detailMessage;
}
public String getMessage() {
return message;
}
public Integer getCode()
{
return code;
}
public ServiceException setMessage(String message)
{
this.message = message;
return this;
}
public ServiceException setDetailMessage(String detailMessage)
{
this.detailMessage = detailMessage;
return this;
}
}
1.4 ErrorEnum：错误枚举类
package com.torinosrc.common.utils.star;
public interface ErrorEnum {
Integer getErrorCode();
String getErrorMsg();
}
2 其他项改动
下面提供一个空指针校验工具类：
2.1 调用示例：
/**
* 根据id查询文章列表
*
* @param article 文章
* @return 文章
*/
@Override
public Article getArticleById(Long id)
{
Article article = baseMapper.selectArticleById(id);
AssertUtils.isNotEmpty(article,"抛出异常");
return article;
}
2.2 AssertUtil：校验工具类
import cn.hutool.core.util.ObjectUtil;
import java.text.MessageFormat;
import java.util.Objects;
/**
* 校验工具类
*/
public class AssertUtil {
//如果不是true，则抛异常
public static void isTrue(boolean expression, String msg) {
if (!expression) {
throwException(msg);
}
}
public static void isTrue(boolean expression, ErrorEnum errorEnum, Object... args) {
if (!expression) {
throwException(errorEnum, args);
}
}
//如果是true，则抛异常
public static void isFalse(boolean expression, String msg) {
if (expression) {
throwException(msg);
}
}
//如果是true，则抛异常
public static void isFalse(boolean expression, ErrorEnum errorEnum, Object... args) {
if (expression) {
throwException(errorEnum, args);
}
}
//如果不是非空对象，则抛异常
public static void isNotEmpty(Object obj, String msg) {
if (isEmpty(obj)) {
throwException(msg);
}
}
//如果不是非空对象，则抛异常
public static void isNotEmpty(Object obj, ErrorEnum errorEnum, Object... args) {
if (isEmpty(obj)) {
throwException(errorEnum, args);
}
}
//如果不是非空对象，则抛异常
public static void isEmpty(Object obj, String msg) {
if (!isEmpty(obj)) {
throwException(msg);
}
}
public static void equal(Object o1, Object o2, String msg) {
if (!ObjectUtil.equal(o1, o2)) {
throwException(msg);
}
}
public static void notEqual(Object o1, Object o2, String msg) {
if (ObjectUtil.equal(o1, o2)) {
throwException(msg);
}
}
private static boolean isEmpty(Object obj) {
return ObjectUtil.isEmpty(obj);
}
private static void throwException(String msg) {
throwException(null, msg);
}
private static void throwException(ErrorEnum errorEnum, Object... arg) {
if (Objects.isNull(errorEnum)) {
errorEnum = BusinessErrorEnum.BUSINESS_ERROR;
}
throw new BusinessException(errorEnum.getErrorCode(), MessageFormat.format(errorEnum.getErrorMsg(), arg));
}
}
2.3 BusinessErrorEnum：业务校验异常码
import lombok.AllArgsConstructor;
import lombok.Getter;
/**
* Description: 业务校验异常码
* Author: <a href="https://github.com/zongzibinbin">abin</a>
* Date: 2023-03-26
*/
@AllArgsConstructor
@Getter
public enum BusinessErrorEnum implements ErrorEnum {
//==================================common==================================
BUSINESS_ERROR(1001, "{0}"),
//==================================user==================================
//==================================chat==================================
SYSTEM_ERROR(1001, "系统出小差了，请稍后再试哦~~"),
;
private Integer code;
private String msg;
@Override
public Integer getErrorCode() {
return code;
}
@Override
public String getErrorMsg() {
return msg;
}
}
2.4 BusinessException：异常实体类
import lombok.Data;
@Data
public class BusinessException extends RuntimeException {
private static final long serialVersionUID = 1L;
/**
* 错误码
*/
protected Integer errorCode;
/**
* 错误信息
*/
protected String errorMsg;
public BusinessException() {
super();
}
public BusinessException(String errorMsg) {
super(errorMsg);
this.errorMsg = errorMsg;
}
public BusinessException(Integer errorCode, String errorMsg) {
super(errorMsg);
this.errorCode = errorCode;
this.errorMsg = errorMsg;
}
public BusinessException(Integer errorCode, String errorMsg, Throwable cause) {
super(errorMsg, cause);
this.errorCode = errorCode;
this.errorMsg = errorMsg;
}
public BusinessException(ErrorEnum error) {
super(error.getErrorMsg());
this.errorCode = error.getErrorCode();
this.errorMsg = error.getErrorMsg();
}
@Override
public String getMessage() {
return errorMsg;
}
@Override
public synchronized Throwable fillInStackTrace() {
return this;
}
}
2.5 ErrorEnum：错误枚举类
public interface ErrorEnum {
Integer getErrorCode();
String getErrorMsg();
}
