Why does the Spring project cause randomness problems due to circular dependencies when starting?

Analysis of circular dependency and randomness problems in Spring project startup

During the Spring project startup process, circular dependencies may cause randomness problems, which vary in different environments and increase debugging difficulty. This article will analyze this phenomenon from the two aspects of JAR package characteristics and Spring Bean loading order.

1. Randomity of JAR package index

The JAR package is essentially a ZIP compressed package, containing index information. Each time a JAR package is built, the index position may be different, which not only happens when built multiple times in the same environment, but also on different machines. This index uncertainty directly affects the order of file reads in JAR packages, causing randomness problems when Spring starts.

Due to the instability of JAR package indexes, the order in which Spring loads class files in JAR packages also becomes uncertain. This uncertainty is particularly prominent when dealing with circular dependencies, because the resolution of circular dependencies depends on the order in which Spring creates and injects beans.

2. The relationship between Spring Bean loading order and JAR package index

When Spring framework starts, all beans are scanned and loaded and initialized in a specific order. When encountering circular dependencies, Spring adopts a level 3 caching mechanism to solve the problem. However, changes in JAR package index order affect the order in which Spring loads beans.

This order difference may cause Spring to fail to handle circular dependencies correctly, which in turn causes project startup failure. Especially when circular dependencies involve multiple beans, this randomness problem is more difficult to predict and solve.

Through the above analysis, we can more effectively deal with the randomness problem caused by circular dependence when starting Spring project. It is recommended to optimize the code structure in development, reduce circular dependencies, and conduct adequate testing in different environments to reduce the impact of such problems.

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