161 Spring Boot 3 Real-World Examples to Supercharge Your Backend Development

Introduction

Spring Boot 3.4.2 based collection of 161 practical cases, continuously updated and freely available as a PDF.

Utility Classes and Code Samples

2.1 AntPathMatcher

Matches strings against Ant‑style path patterns, useful for URL routing and security configuration.

AntPathMatcher matcher = new AntPathMatcher();
boolean match1 = matcher.match("/users/*", "/users/123");
boolean match2 = matcher.match("/users/**", "/users/123/orders");
boolean match3 = matcher.match("/user?", "/user1");
Map<String, String> vars = matcher.extractUriTemplateVariables("/users/{id}", "/users/42");
System.err.printf("match1 = %s, match2 = %s, match3 = %s, vars = %s%n", match1, match2, match3, vars);

Output:

match1 = true, match2 = true, match3 = true, vars = {id=42}

2.2 PatternMatchUtils

Provides simple wildcard pattern matching methods.

boolean match1 = PatternMatchUtils.simpleMatch("user*", "username");
boolean match2 = PatternMatchUtils.simpleMatch("user?", "user1");
boolean match3 = PatternMatchUtils.simpleMatch(new String[]{"user*", "admin*"}, "adminuser");
System.err.printf("match1 = %s, match2 = %s, match3 = %s%n", match1, match2, match3);

Output:

match1 = true, match2 = false, match3 = true

2.3 PropertyPlaceholderHelper

Resolves placeholders like ${name} in strings using a given property source.

PropertyPlaceholderHelper helper = new PropertyPlaceholderHelper("${", "}");
Properties props = new Properties();
props.setProperty("name", "Spring Boot3实战案例200讲");
props.setProperty("title", "标题：${name}!");
String result = helper.replacePlaceholders("${title}", props::getProperty);
System.err.printf("result = %s%n", result);

Output:

result = 标题：Spring Boot3实战案例200讲!

2.4 MultiValueMap

Extended Map allowing multiple values per key.

MultiValueMap<String, String> map = new LinkedMultiValueMap<>();
map.add("colors", "red");
map.add("colors", "blue");
map.add("sizes", "large");
List<String> colors = map.get("colors");
System.err.printf("colors: %s%n", colors);

Output:

colors: [red, blue]

2.5 ConcurrentReferenceHashMap

Thread‑safe map based on soft references, suitable for cache scenarios.

// Create a high‑concurrency cache map
Map<String, Object> cache = new ConcurrentReferenceHashMap<>();
// Value can be reclaimed when memory is low
cache.put("key", new Object());

2.6 SystemPropertyUtils

Resolves placeholders using JVM system properties.

String javaHome = SystemPropertyUtils.resolvePlaceholders("${java.home}");
String defaultValue = SystemPropertyUtils.resolvePlaceholders("${unknown.property:default_value}");
System.err.printf("javaHome: %s, defaultValue = %s%n", javaHome, defaultValue);

Output:

javaHome: D:\jdk-21.0.1, defaultValue = default_value

2.7 ReflectionUtils

Utility for low‑level reflection tasks.

UserDTO dto = new UserDTO();
Field field = ReflectionUtils.findField(UserDTO.class, "name");
ReflectionUtils.makeAccessible(field);
ReflectionUtils.setField(field, dto, "John");
Method method = ReflectionUtils.findMethod(UserDTO.class, "setAge", int.class);
ReflectionUtils.invokeMethod(method, dto, 30);

2.8 MethodInvoker

Conveniently prepares and invokes a method with arguments.

MethodInvoker invoker = new MethodInvoker();
invoker.setTargetObject(new UserDTO());
invoker.setTargetMethod("calcAge");
invoker.setArguments(100, 0.2);
invoker.prepare();
Object result = invoker.invoke();

2.9 ResourceUtils

Loads resources from classpath or URLs.

File file = ResourceUtils.getFile("classpath:config.properties");
boolean isUrl = ResourceUtils.isUrl("http://example.com");
URL url = ResourceUtils.getURL("classpath:data.json");
System.err.printf("file = %s, isUrl = %s, url = %s%n", file, isUrl, url);

2.10 WebUtils

Utilities for web‑related tasks such as retrieving cookies or request parameters.

HttpServletRequest request = null;
Cookie cookie = WebUtils.getCookie(request, "sessionId");
String id = WebUtils.findParameterValue(request, "id");

2.11 UriUtils

Encodes and decodes URI components per RFC 3986.

String encoded = UriUtils.encodePathSegment("path with spaces", StandardCharsets.UTF_8);
String decoded = UriUtils.decode(encoded, StandardCharsets.UTF_8);
System.err.printf("encoded: %s, decoded = %s%n", encoded, decoded);

Output:

encoded: path%20with%20spaces, decoded = path with spaces

2.12 UriComponentsBuilder

Fluent builder for constructing URIs.

URI uri = UriComponentsBuilder.fromUriString("https://www.pack.com")
    .path("/products/{id}")
    .queryParam("category", "books")
    .build("123");
System.err.println(uri);

Output:

https://www.pack.com/products/123?category=books

2.13 HtmlUtils

Escapes and unescapes HTML to prevent XSS.

String escaped = HtmlUtils.htmlEscape("<script>alert('XSS')</script>");
System.err.println(escaped);
String unescaped = HtmlUtils.htmlUnescape("<b>Bold</b>");
System.err.println(unescaped);

Output: <script>alert('XSS')</script> and

<b>Bold</b>

2.14 ObjectUtils

Null‑safe utilities for objects, arrays, and collections.

boolean isEmpty1 = ObjectUtils.isEmpty(null);
boolean isEmpty2 = ObjectUtils.isEmpty(new int[0]);
Object obj1 = null;
Object obj2 = new Object();
boolean equals = ObjectUtils.nullSafeEquals(obj1, obj2);
System.err.printf("isEmpty1 = %s, isEmpty2 = %s, equals = %s%n", isEmpty1, isEmpty2, equals);

Output:

isEmpty1 = true, isEmpty2 = true, equals = false

2.15 DateFormatter

Flexible formatter for java.util.Date.

DateFormatter formatter = new DateFormatter("yyyy-MM-dd HH:mm:ss");
String result = formatter.print(new Date(), Locale.getDefault());
System.err.println(result);

Sample output:

2025-08-16 09:11:57

2.16 JsonParserFactory

Factory for obtaining a lightweight JSON parser.

JsonParser parser = JsonParserFactory.getJsonParser();
Map<String, Object> map = parser.parseMap("{\"name\":\"Spring Boot3实战案例200讲\",\"age\":33}");
List<Object> list = parser.parseList("[1, 2, 3]");
System.err.printf("map = %s, list = %s%n", map, list);

Output:

map = {name=Spring Boot3实战案例200讲, age=33}, list = [1, 2, 3]

2.17 ResolvableType

Handles complex generic types at runtime.

private List<UserDTO> list = new ArrayList<>();
public static void main(String[] args) throws Exception {
    ResolvableType listType = ResolvableType.forField(ResolvableTypeTest.class.getDeclaredField("list"));
    ResolvableType elementType = listType.getGeneric(0);
    ResolvableType mapType = ResolvableType.forClassWithGenerics(Map.class, String.class, Integer.class);
    System.err.printf("elementType = %s%nmapType = %s%n", elementType, mapType);
}

Output: elementType = com.pack.utils.ReflectionUtilsTest$UserDTO and

mapType = java.util.Map<java.lang.String, java.lang.Integer>

2.18 CacheControl

Builder for HTTP Cache‑Control header values.

CacheControl cacheControl = CacheControl.maxAge(1, TimeUnit.HOURS)
    .noTransform()
    .mustRevalidate();
String headerValue = cacheControl.getHeaderValue();
System.err.println(headerValue);

Output:

max-age=3600, must-revalidate, no-transform

2.19 DefaultConversionService

Default Spring conversion service for type conversion.

DefaultConversionService conversionService = new DefaultConversionService();
Integer intValue = conversionService.convert("42", Integer.class);
Boolean boolValue = conversionService.convert("true", Boolean.class);
System.err.printf("intValue = %s, boolValue = %s%n", intValue, boolValue);

Output:

intValue = 42, boolValue = true

2.20 MediaTypeFactory

Detects MIME type from a filename.

Optional<MediaType> mediaType = MediaTypeFactory.getMediaType("document.pdf");
mediaType.ifPresent(System.out::println);

Output:

application/pdf

2.21 MimeTypeUtils

Provides common MIME type constants and utilities.

MimeType a = MimeTypeUtils.APPLICATION_JSON;
MimeType b = MimeType.valueOf("application/*");
boolean ret = a.isCompatibleWith(b);
System.err.println(ret);

Output:

true

2.22 PropertySource

Handles property values from custom sources.

StandardEnvironment environment = new StandardEnvironment();
Map<String, Object> props = new HashMap<>();
props.put("pack.app.title", "Spring Boot3实战案例200讲");
PropertySource<?> source = new MapPropertySource("my-properties", props);
environment.getPropertySources().addFirst(source);

2.23 LocaleContextHolder

Stores the current thread's Locale for i18n.

Locale currentLocale = LocaleContextHolder.getLocale();
LocaleContextHolder.setLocale(Locale.CHINA);
System.err.println(currentLocale);

Output: zh_CN All 161 cases are available for free download as a PDF, with permanent updates for subscribers.