# Springboot-Layui

**Repository Path**: front-devops/springboot-layui

## Basic Information

- **Project Name**: Springboot-Layui
- **Description**: sanbuliuxin/springboot-layui
- **Primary Language**: Java
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2021-04-18
- **Last Updated**: 2024-03-06

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# SpringBoot Layui  
基于SpringBoot2.x + layui2.5.x + Thymeleaf + Mysql5.7 版本开发的后台管理系统

## 问题记录
1. springDataJpa动态代理扩展  
    给所有的DAO接口添加相同的默认方法：
   https://blog.csdn.net/weixin_45138931/article/details/102979230  
   https://www.petrikainulainen.net/programming/spring-framework/spring-data-jpa-tutorial-adding-custom-methods-into-all-repositories/
   
1. JPA 通过@Query和JPQL分页查询
    ```java
    //JPQL
    @Query(value = "SELECT u FROM User u ORDER BY id")
    Page<User> findAllUsersWithPagination(Pageable pageable);
    
    // Native
    @Query(
            value = "SELECT * FROM Users ORDER BY id",
            countQuery = "SELECT count(*) FROM Users",
            nativeQuery = true)
    Page<User> findAllUsersWithPagination(Pageable pageable);
    ```
1. Mysql 5.7 创建create_time和update_time字段自动更新
   ```mysql
    `create_time` datetime(0) NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
    `update_time` datetime(0) NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP(0) COMMENT '更新时间',
   ```   
   
1. JPA 存在updateTime字段时，更新Entity对象，如果updateTime为Null，会导致数据库不自动更新update_time字段,并设置成NULL
   ```java
    @EnableJpaAuditing
    @SpringBootApplication
    public class Springboot2DemoApplication {}
   
    // @LastModifiedDate 自动设置updateTime
    @Column(name = "update_time")
    @Temporal(TemporalType.TIMESTAMP)
    @JsonFormat
    @LastModifiedDate
    private Date updateTime;
   ```

1. Ignoring null Parameters Using the @Query Annotation
    ```java
    @Query("SELECT c FROM Customer c WHERE (:name is null or c.name = :name) and (:email is null"
      + " or c.email = :email)")
    List<Customer> findCustomerByNameAndEmail(@Param("name") String name, @Param("email") String email);
    ```
1. HTML通过flex实现左右DIV布局
    ```html
    <div style="display: flex;
              flex-flow: row nowrap;
              justify-content: space-between;">
        <div>left</div>
        <div>right</div>
    </div>
    ```
1. thymeleaf th:href添加URL参数
    ```html
    <a th:href="@{/index(param1='value1',param2='value2')}">
    ```
1. thymeleaf 获取当前Request中的参数、Session参数
   somesite.com/login?error=true
    ```html
      <div id="errors" th:if="${(param.error != null) and (param.error[0] == 'true')}">
        Input is incorrect
        </div>
    ```
   
   session params
   ```thymeleaf
    ${session.foo} // Retrieves the session atttribute 'foo'
    ${session.size()}
    ${session.isEmpty()}
    ${session.containsKey('foo')}
   ```

1. thymeleaf Null 安全
    ```html
    <td th:text="${user?.address?.city}"></td>
   <span th:text="${object.property} ? 'this is good' : 'default value'"></span>
   <span th:text="${object.property} ?: 'default value'"></span>
    ```
1. thymeleaf 字符串isEmpty判断
   ```html
   ${#strings.isEmpty(name)}
   
   // is true if name is not empty
   ${!#strings.isEmpty(name)} or ${not #strings.isEmpty(name)} 
   ```