CWE-595 错误对对象引用当作对象内容进行比较

Comparison of Object References Instead of Object Contents

结构: Simple

Abstraction: Variant

状态: Incomplete

被利用可能性: unkown

基本描述

The program compares object references instead of the contents of the objects themselves, preventing it from detecting equivalent objects.

扩展描述

For example, in Java, comparing objects using == usually produces deceptive results, since the == operator compares object references rather than values; often, this means that using == for strings is actually comparing the strings' references, not their values.

相关缺陷

• cwe_Nature: ChildOf cwe_CWE_ID: 1025 cwe_View_ID: 1000 cwe_Ordinal: Primary

适用平台

Language: [{'cwe_Name': 'Java', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'JavaScript', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Name': 'PHP', 'cwe_Prevalence': 'Undetermined'}, {'cwe_Class': 'Language-Independent', 'cwe_Prevalence': 'Undetermined'}]

常见的影响

可能的缓解方案

Implementation

策略:

In Java, use the equals() method to compare objects instead of the == operator. If using ==, it is important for performance reasons that your objects are created by a static factory, not by a constructor.

示例代码

例

In the example below, two Java String objects are declared and initialized with the same string values and an if statement is used to determine if the strings are equivalent.

bad Java

However, the if statement will not be executed as the strings are compared using the "==" operator. For Java objects, such as String objects, the "==" operator compares object references, not object values. While the two String objects above contain the same string values, they refer to different object references, so the System.out.println statement will not be executed. To compare object values, the previous code could be modified to use the equals method:

good

例

In the following Java example, two BankAccount objects are compared in the isSameAccount method using the == operator.

bad Java

Using the == operator to compare objects may produce incorrect or deceptive results by comparing object references rather than values. The equals() method should be used to ensure correct results or objects should contain a member variable that uniquely identifies the object.

The following example shows the use of the equals() method to compare the BankAccount objects and the next example uses a class get method to retrieve the bank account number that uniquely identifies the BankAccount object to compare the objects.

good Java

分类映射

引用

• REF-954 Equality comparisons and sameness

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