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Today, I'll show you how to set the map results returned by mybatis in order. The content of the article is good. Now I would like to share it with you. Friends who feel in need can understand it. I hope it will be helpful to you. Let's read it along with the editor's ideas.

The map result returned by mybatis is set in order.

The map results returned by mybatis are set in order (consistent with the domain order of the query)

In this case, there is no sort.

If you want to come in the order of inquiry

Replace it with

Orderly display of query results in mybatis

How to display the results of sql query in mybatis in an orderly manner according to the self-defined resultMap?

1. Analyze why the result is out of order

Take a look at the following picture first:

The first is a select statement, and resultType is a class encapsulated by this project.

The second is the resultMap statement. Type is also a class encapsulated by this project.

The third is a class encapsulated by this project. You can see that it inherits HashMap.

From the above figure, we can see that most of the data accessed by HashMap are out of order, so the key points are found.

To get the results in order, replace HashMap with LinkedHashMap

2. Modification

Because the PageData wrapper class is also used elsewhere in this project, I only change the

Change resultType to java.util.LinkedHashMap

Change typeype to java.util.LinkedHashMap

Supplement

HashMap:

HashMap is the most commonly used Map, it stores data according to the HashCode value of the key, and its value can be obtained directly according to the key, so it has fast access speed.

HashMap can only allow the key of one record to be Null

Allow the value of multiple records to be Null

HashMap does not support thread synchronization, that is, multiple threads can write HashMap at any one time.

May lead to data inconsistencies.

LinkedHashMap:

LinkedHashMap is also a HashMap, but maintains a two-way linked list internally, which can keep the order.

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