Introducing the solution for mybatis lazy loading-javaTutorial-php.cn

Home

Java

javaTutorial

Introducing the solution for mybatis lazy loading

Y2J

May 13, 2017 am 10:36 AM

java

This article mainly introduces the detailed explanation of delayed loading in the mybatis tutorial. The meaning and usage implementation of lazy loading are introduced in detail. Those who are interested can learn about

lazy loading

1 The meaning of using lazy loading

When performing data query, in order to improve database query performance, try to use single table query, because single table query is faster than multi-table related query.

If querying a single table can meet the needs, query the single table at the beginning. When related information is needed, then related query. When related information is needed, query again. This is called delayed loading.

The resultMap in mybatis provides the delayed loading function, and the delayed loading is configured through the resultMap.

2 Configure mybatis to support delayed loading

##Configure global parameters in SqlMapConfig.xml:

<!-- 全局配置参数 --> 
 
<settings> 
 
<!-- 延迟加载总开关 --> 
 
<setting name="lazyLoadingEnabled" value="true" /> 
 
<!-- 设置按需加载 --> 
 
<setting name="aggressiveLazyLoading" value="false" /> 
 
</settings>

Copy after login

3 Lazy loading implementation

3.1 Implementation ideas

Requirements:

Query order and user information, one-to-one query.

Only query order information at the beginning

When a user is needed, call the getUser() method in the Orders class to perform lazy loading and issue SQL to the database.

3.2 mapper.xml

<!-- 一对一查询延迟加载 
   开始只查询订单，对用户信息进行延迟加载  
   --> 
   <select id="findOrderUserListLazyLoading" resultMap="orderCustomLazyLoading"> 
     SELECT  
     orders.* 
    FROM 
     orders 
   </select>

Copy after login

3.3 resultMap

<!-- 一对一查询延迟加载 的配置 --> 
  <resultMap type="orders" id="orderCustomLazyLoading"> 
    <!-- 完成了订单信息的映射配置 --> 
    <!-- id：订单关联用户查询的唯 一 标识 --> 
    <id column="id" property="id" /> 
    <result column="user_id" property="userId" /> 
    <result column="number" property="number" /> 
    <result column="createtime" property="createtime" /> 
    <result column="note" property="note" /> 
    <!-- 配置用户信息的延迟加载 select：延迟加载执行的sql所在的statement的id，如果不在同一个namespace需要加namespace  
      sql：根据用户id查询用户信息 column：关联查询的列 property:将关联查询的用户信息设置到Orders的哪个属性 --> 
    <association property="user" 
      select="com.sihai.mybatis.mapper.UserMapper.findUserById" column="user_id"></association> 
 
 
  </resultMap>

Copy after login

3.4 mapper.java

//一对一查询，延迟加载 
  public List<Orders> findOrderUserListLazyLoading() throws Exception;

Copy after login

3.5 Test code

// 一对一查询延迟加载 
  @Test 
  public void testFindOrderUserListLazyLoading() throws Exception { 
 
    SqlSession sqlSession = sqlSessionFactory.openSession(); 
    // 创建mapper代理对象 
    OrdersMapperCustom ordersMapperCustom = sqlSession 
        .getMapper(OrdersMapperCustom.class); 
 
    // 调用方法 
    List<Orders> list = ordersMapperCustom.findOrderUserListLazyLoading(); 
     
    //这里执行延迟加载，要发出sql 
    User user = list.get(0).getUser(); 
    System.out.println(user); 
     
  }

Copy after login

4 summary of resultType, resultMap, lazy loading usage scenarios

##4.1 Lazy loading:

There are many ways to implement delayed loading. Querying only a single table can meet the needs. In order to improve database query performance, lazy loading is used and then the related information is queried. Mybatis provides lazy loading function for service layer.

4.2 resultType:

Function: Map the query results to the pojo according to the consistency of the sql column name pojo attribute name.

Occasion: It is common to display some detailed records. When all related query information is displayed on the page, you can directly use resultType to map each record to the pojo, and traverse the list on the front-end page (list (in the middle is pojo).

4.3 resultMap:

Use association and collection to complete one-to-one and one-to-many advanced mapping.

4.4 association:

Function: Map association query information to a pojo class.

Occasion: In order to conveniently obtain related information, you can use association to map related orders to POJO, such as querying orders and related user information.

4.5 collection:

Function: Map related query information to a list collection.

Occasion: In order to conveniently obtain related information, you can use collection to map the related information to the list collection. For example: to query user permission scope modules and functions, you can use collection to map the module and function lists to the list. .

【Related Recommendations】

Special Recommendation

:"php Programmer Toolbox" V0.1 version Download2. Java free video tutorial

3. Comprehensive analysis of Java annotations

The above is the detailed content of Introducing the solution for mybatis lazy loading. For more information, please follow other related articles on the PHP Chinese website!

Statement of this Website

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn

Hot AI Tools

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress images for free

Clothoff.io

AI clothes remover

Video Face Swap

Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Assassin's Creed Shadows: Seashell Riddle Solution

4 weeks ago By DDD

What's New in Windows 11 KB5054979 & How to Fix Update Issues

3 weeks ago By DDD

Where to find the Crane Control Keycard in Atomfall

4 weeks ago By DDD

Roblox: Dead Rails - How To Complete Every Challenge

1 months ago By DDD

How to fix KB5055523 fails to install in Windows 11?

2 weeks ago By DDD

Hot Tools

Notepad++7.3.1

Easy-to-use and free code editor

SublimeText3 Chinese version

Chinese version, very easy to use

Zend Studio 13.0.1

Powerful PHP integrated development environment

Dreamweaver CS6

Visual web development tools

SublimeText3 Mac version

God-level code editing software (SublimeText3)

Hot Topics

Where is the login entrance for gmail email?

7723

Java Tutorial

1643

CakePHP Tutorial

1396

Laravel Tutorial

1290

PHP Tutorial

1233

Related knowledge

Java Spring Interview Questions Aug 30, 2024 pm 04:29 PM

In this article, we have kept the most asked Java Spring Interview Questions with their detailed answers. So that you can crack the interview.

Break or return from Java 8 stream forEach? Feb 07, 2025 pm 12:09 PM

Java 8 introduces the Stream API, providing a powerful and expressive way to process data collections. However, a common question when using Stream is: How to break or return from a forEach operation? Traditional loops allow for early interruption or return, but Stream's forEach method does not directly support this method. This article will explain the reasons and explore alternative methods for implementing premature termination in Stream processing systems. Further reading: Java Stream API improvements Understand Stream forEach The forEach method is a terminal operation that performs one operation on each element in the Stream. Its design intention is

TimeStamp to Date in Java Aug 30, 2024 pm 04:28 PM

Guide to TimeStamp to Date in Java. Here we also discuss the introduction and how to convert timestamp to date in java along with examples.

PHP: A Key Language for Web Development Apr 13, 2025 am 12:08 AM

PHP is a scripting language widely used on the server side, especially suitable for web development. 1.PHP can embed HTML, process HTTP requests and responses, and supports a variety of databases. 2.PHP is used to generate dynamic web content, process form data, access databases, etc., with strong community support and open source resources. 3. PHP is an interpreted language, and the execution process includes lexical analysis, grammatical analysis, compilation and execution. 4.PHP can be combined with MySQL for advanced applications such as user registration systems. 5. When debugging PHP, you can use functions such as error_reporting() and var_dump(). 6. Optimize PHP code to use caching mechanisms, optimize database queries and use built-in functions. 7

Java Program to Find the Volume of Capsule Feb 07, 2025 am 11:37 AM

Capsules are three-dimensional geometric figures, composed of a cylinder and a hemisphere at both ends. The volume of the capsule can be calculated by adding the volume of the cylinder and the volume of the hemisphere at both ends. This tutorial will discuss how to calculate the volume of a given capsule in Java using different methods. Capsule volume formula The formula for capsule volume is as follows: Capsule volume = Cylindrical volume Volume Two hemisphere volume in, r: The radius of the hemisphere. h: The height of the cylinder (excluding the hemisphere). Example 1 enter Radius = 5 units Height = 10 units Output Volume = 1570.8 cubic units explain Calculate volume using formula: Volume = π × r2 × h (4

PHP vs. Python: Understanding the Differences Apr 11, 2025 am 12:15 AM

PHP and Python each have their own advantages, and the choice should be based on project requirements. 1.PHP is suitable for web development, with simple syntax and high execution efficiency. 2. Python is suitable for data science and machine learning, with concise syntax and rich libraries.

Create the Future: Java Programming for Absolute Beginners Oct 13, 2024 pm 01:32 PM

Java is a popular programming language that can be learned by both beginners and experienced developers. This tutorial starts with basic concepts and progresses through advanced topics. After installing the Java Development Kit, you can practice programming by creating a simple "Hello, World!" program. After you understand the code, use the command prompt to compile and run the program, and "Hello, World!" will be output on the console. Learning Java starts your programming journey, and as your mastery deepens, you can create more complex applications.

How to Run Your First Spring Boot Application in Spring Tool Suite? Feb 07, 2025 pm 12:11 PM

Spring Boot simplifies the creation of robust, scalable, and production-ready Java applications, revolutionizing Java development. Its "convention over configuration" approach, inherent to the Spring ecosystem, minimizes manual setup, allo

See all articles