Master Spring Boot 3: 5 Real-World Cases & Code Samples

Spring Boot 3 practical case collection (123 examples) provides ready‑to‑use code for common backend tasks.

JSON Parsing Tools

When parsing JSON strings you can use Jackson (direct injection or manual creation) or Gson. Spring Boot also offers a factory that automatically selects the appropriate parser.

<code>// Injection
@Resource
private ObjectMapper objectMapper;

// Manual creation
ObjectMapper mapper = new ObjectMapper();

// Gson example
Gson gson = new GsonBuilder().create();

// Factory usage
String json = """
{
  "name": "pack",
  "sex": "男",
  "age": 22,
  "idNo": "640522199303092164"
}
""";
JsonParser jsonParser = JsonParserFactory.getJsonParser();
Map<String, Object> ret = jsonParser.parseMap(json);
System.err.println(ret);
</code>

Output result:

<code>{name=pack, sex=男, age=22, idNo=640522199303092164}</code>

Factory internal implementation:

Executing Database Scripts

Define a bean to run SQL scripts automatically at startup.

<code>@Configuration
public class DatabaseScriptExecution {
    @Bean
    DataSourceScriptDatabaseInitializer databaseInitializer(DataSource dataSource) {
        DatabaseInitializationSettings settings = new DatabaseInitializationSettings();
        settings.setEncoding(StandardCharsets.UTF_8);
        settings.setSchemaLocations(List.of("classpath:db/db.sql", "optional:classpath:db/data.sql"));
        return new DataSourceScriptDatabaseInitializer(dataSource, settings);
    }
}
</code>

Spring Boot can also execute scripts via configuration:

<code>spring:
  sql:
    init:
      mode: always
      username: root
      password: xxxooo
      encoding: UTF-8
      schema-locations:
        - optional:classpath:db/schema.sql
      data-locations:
        - optional:classpath:db/data.sql
</code>

Custom DataSource Configuration

Use DataSourceBuilder to create a custom DataSource bean.

<code>@Configuration
public class DataSourceConfig {
    @Bean
    DataSource createDataSource() {
        return DataSourceBuilder.create()
            .type(HikariDataSource.class)
            .driverClassName("com.mysql.cj.jdbc.Driver")
            .url("jdbc:mysql://localhost:3306/ds2")
            .username("root")
            .password("xxxooo")
            .build();
    }
}
</code>

Supported connection‑pool implementations: Hikari, Tomcat JDBC Pool, Apache DBCP2, Oracle UCP, C3P0.

Properties & YAML Parsing

Load a properties file:

<code>PropertiesPropertySourceLoader loader = new PropertiesPropertySourceLoader();
ClassPathResource resource = new ClassPathResource("user.properties");
List<PropertySource<?>> sources = loader.load("user", resource);
sources.forEach(source -> System.err.println(source.getName() + "@" + source.getSource()));
</code>

Result:

<code>user@{pack.name=pack, pack.version=1.0.0, pack.title=xxxooo}</code>

Load a YAML file similarly or define a bean:

<code>@Bean
YamlPropertiesFactoryBean yamlFactoryBean() {
    YamlPropertiesFactoryBean factory = new YamlPropertiesFactoryBean();
    factory.setResources(new ClassPathResource("user.yaml"));
    return factory;
}
</code>

Data Binding

Bind configuration properties to an object using Binder :

<code>StandardEnvironment env = new StandardEnvironment();
env.getPropertySources().addFirst(new SimpleCommandLinePropertySource("--pack.title=xxxooo", "--pack.version=1.0.0"));
Binder binder = Binder.get(env);
BindResult<App> result = binder.bind("pack", App.class);
System.err.println(result.get());
record App(String title, String version) {}
</code>

Bind request parameters:

<code>DataBinder binder = new DataBinder(new App());
PropertyValues values = new ServletRequestParameterPropertyValues(request);
binder.bind(values);
Object target = binder.getTarget();
</code>

Validate bound data:

<code>DataBinder binder = new DataBinder(new App());
binder.setValidator(validator);
binder.validate();
binder.getBindingResult().getFieldErrors().forEach(error ->
    System.err.println(error.getField() + " @ " + error.getDefaultMessage()));
public class App {
    @NotEmpty(message = "标题不能空")
    private String title;
    private String version;
}
</code>