Detailed SpringBoot tutorial data access

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In fact, JDBC is more primitive database access, but have to say, a lot of things are based on it to encapsulate, and there are a lot of projects like using JDBC, so when we learn, or need to understand JDBC related, but here we force JDBC principle to explain, Since we are beyond the scope of this blog post, we will only talk about how to use JDBC. Using JDBC in SpringBoot is very simple. Here we use the Idea wizard to create a new project. When checking dependencies, we check mysql Dirver and JDBC in addition to checking web modules as usual



After creating the project, the pom.xml package will look something like this. Of course, you can also create a Maven project and import dependencies in this way



Once the project is created, how do we use it? It is very simple, we just need to do some configuration in the main configuration file, such as the database account password, here to say that we use mysql relational database, as follows



We can write the following code to test in the test class to see if the connection is successful. If the connection is not successful, an error will be reported. If it runs normally, the connection is successful.



Here we can see the console output log, we can know that SpringBoot default to be class com. Zaxxer. Hikari. HikariDataSource as data source, and the relevant configuration in DataSourceProperties are data source.

If we create SQL directly under Resources and do not configure it in any configuration file, we need to name the SQL specifically to make it effective. Of course, we usually configure the SQL in the main configuration file, as follows

Schema - *. SQL, data - *. SQL
Default rules: schema. SQL, schema-all. SQL;
You can use   
	schema:
      - classpath:department.sql
      The specified location
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The default Hikari data source for SpringBoot is Hikari, and the default Hikari data source for SpringBoot is Hikari. The default Hikari data source is Hikari, and the default Hikari data source is Hikari. But it feels longer)



I first imported the Druid data source into my project, and then created a configuration class in the Config directory to control Druid. I tested the configuration class as follows, using filters and listeners as examples

@Configuration
public class DruidConfig {

    @ConfigurationProperties(prefix = "spring.datasource")
    @Bean
    public DataSource druid(a){
       return  new DruidDataSource();
    }

    // Configure Druid monitoring
    // configure a Servlet to manage the background
    @Bean
    public ServletRegistrationBean statViewServlet(a){
        ServletRegistrationBean bean = new ServletRegistrationBean(new StatViewServlet(), "/druid/*");
        Map<String,String> initParams = new HashMap<>();

        initParams.put("loginUsername"."admin");
        initParams.put("loginPassword"."123456");
        initParams.put("allow"."");// All access is allowed by default
        initParams.put("deny"."192.168.15.21");

        bean.setInitParameters(initParams);
        return bean;
    }


    //2. Configure a filter for web monitoring
    @Bean
    public FilterRegistrationBean webStatFilter(a){
        FilterRegistrationBean bean = new FilterRegistrationBean();
        bean.setFilter(new WebStatFilter());

        Map<String,String> initParams = new HashMap<>();
        initParams.put("exclusions"."*.js,*.css,/druid/*");

        bean.setInitParameters(initParams);

        bean.setUrlPatterns(Arrays.asList("/ *"));

        returnbean; }}Copy the code

First create a Mapper package under SRC, then create the mapper interface for the corresponding entity under the package, as shown below

// Specify that this is a mapper that operates on a database
@Mapper
public interface DepartmentMapper {

    @Select("select * from department where id=#{id}")
    public Department getDeptById(Integer id);

    @Delete("delete from department where id=#{id}")
    public int deleteDeptById(Integer id);

    @Options(useGeneratedKeys = true,keyProperty = "id")
    @Insert("insert into department(departmentName) values(#{departmentName})")
    public int insertDept(Department department);

    @Update("update department set departmentName=#{departmentName} where id=#{id}")
    public int updateDept(Department department);
}
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SpringBoot has a custom configuration rule for MyBatis. Add a ConfigurationCustomizer to the container, and use MapperScan to batch scan all Mapper interfaces.

@org.springframework.context.annotation.Configuration
public class MyBatisConfig {

    @Bean
    public ConfigurationCustomizer configurationCustomizer(a){
        return new ConfigurationCustomizer(){

            @Override
            public void customize(Configuration configuration) {
                configuration.setMapUnderscoreToCamelCase(true); }}; }}Copy the code

@MapperScan(value = "com.atguigu.springboot.mapper")
@SpringBootApplication
public class SpringBoot06DataMybatisApplication {

	public static void main(String[] args) { SpringApplication.run(SpringBoot06DataMybatisApplication.class, args); }}Copy the code

SpringData provides us with a unified API for manipulating the data access layer; This is primarily done by the Spring Data Commons project. Spring Data Commons allows us to use both relational and non-relational Data access technologies based on a unified Spring standard that includes CRUD (Create, get, update, delete), query, sort, and paging operations.



SpringDataJPA has a Repository interface such as Repository<T, ID extends Serializable> RevisionRepository<T, ID extends Serializable, N extends Number & Comparable> Basic CRUD operations, PagingAndSortingRepository ID extends the Serializable > < T, ID extends the Serializable > : basic CRUD and paging

Here we roughly introduced SpringBoot data access methods, take you to understand some basic operations, more specific also need to learn about the relevant data access methods, the next blog post we will explain the startup principle of SpringBoot.