The type XXX cannot be resolved

出现这种原因一般是jar引用不正确,需要在jar中查找是否有XXX。

比如我在引用的是commons-lang3-3.3.2.jar,但是程序报错说“The type org.apache.commons.lang.exception.NestableException cannot be resolved”,然后我就在commons-lang3-3.3.2.jar中查找,却是没有找到org.apache.commons.lang.exception.NestableException类,所以换成commons-logging-1.2.jar之后就可以了,貌似最新的commons-lang3-3.3.2.jar中全部是org.apache.commons.lang3.xxx开始的,换成以前的版本commons-logging-1.2.jar则没有问题。

Description Resource Path Location Type AfterEach cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 15 Java Problem BeforeEach cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 11 Java Problem Syntax error on token "*", delete this token MetroTicketTest.java /aa/src/aa line 3 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 19 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 29 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 36 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 43 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 50 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 57 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 64 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 71 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 78 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 86 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 94 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 102 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 110 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 118 Java Problem Test cannot be resolved to a type MetroTicketTest.java /aa/src/aa line 126 Java Problem The method assertEquals(String, String) is undefined for the type MetroTicketTest MetroTicketTest.java /aa/src/aa line 27 Java Problem The method assertEquals(String, String) is undefined for the type MetroTicketTest MetroTicketTest.java /aa/src/aa line 34 Java Problem The method assertEquals(String, String) is undefined for the type MetroTicketTest MetroTicketTest.j
03-29
### 解析 Eclipse 中 "Type Connection cannot be resolved to a type" 错误 当遇到 `Type Connection cannot be resolved to a type` 的错误提示时,这通常意味着 Eclipse 未能识别 Java SQL 库中的 `Connection` 类型。以下是几种可能的原因及解决方案: #### 1. 配置 JDBC Driver 如果项目试图通过 JDBC 连接 MySQL 数据库,则需确保已正确引入相应的驱动程序。对于 MySQL 版本较高的情况,如 MySQL 8.x,应确认使用的是兼容的 JDBC 驱动器版本。 ```xml <!-- Maven pom.xml --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.XX</version> <!-- 使用最新稳定版 --> </dependency> ``` #### 2. 更新 Build Path 和 JRE 设置 有时即使全局设置了 JDK 路径,在特定项目中仍可能存在不匹配的情况。因此建议针对具体项目调整其构建路径以及关联的 JRE 环境至合适的版本[^4]。 - 右键点击项目 -> Properties -> Java Build Path -> Libraries Tab. - 移除旧有的 JRE System Library 并添加新的合适版本. #### 3. 导入必要的类文件 为了使 IDE 认识到 `Connection`, 必须显式声明所需的包: ```jsp <%@ page language="java" import="java.sql.Connection, java.sql.DriverManager"%> ``` 上述代码片段展示了如何在 JSP 页面内导入所需类以便于后续操作数据库连接对象[^2]. #### 4. 清理并重建工程 清理工作空间有助于消除潜在缓存问题引起的各种异常状况;而重新编译则能促使最新的更改生效。 - Project Menu -> Clean... - Select All Projects And Click OK Button To Proceed With Cleaning Process. - After Completion Of The Above Step, Try Rebuilding Your Entire Workspace By Going Through Same Menu Again But Choosing 'Build All' Option This Time Around Instead. 以上措施综合运用往往能够有效处理此类编译期类型解析失败的问题。
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