本文整理了Java中org.springframework.util.CollectionUtils类的一些代码示例，展示了CollectionUtils类的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。CollectionUtils类的具体详情如下：
包路径：org.springframework.util.CollectionUtils
类名称：CollectionUtils

CollectionUtils介绍

[英]Miscellaneous collection utility methods. Mainly for internal use within the framework.
[中]杂项收集实用程序方法。主要用于框架内的内部使用。

代码示例

代码示例来源：origin: spring-projects/spring-framework

private void resolveResourceLocations() {
  if (CollectionUtils.isEmpty(this.locationValues)) {
    return;
  }
  else if (!CollectionUtils.isEmpty(this.locations)) {
    throw new IllegalArgumentException("Please set either Resource-based \"locations\" or " +
        "String-based \"locationValues\", but not both.");
  }
  Assert.notNull(this.resourceLoader,
      "ResourceLoader is required when \"locationValues\" are configured.");
  for (String location : this.locationValues) {
    Resource resource = this.resourceLoader.getResource(location);
    this.locations.add(resource);
  }
}

代码示例来源：origin: spring-projects/spring-framework

@Override
  public void printValue(String label, @Nullable Object value) {
    if (value != null && value.getClass().isArray()) {
      value = CollectionUtils.arrayToList(value);
    }
    writer.println(String.format("%17s = %s", label, value));
  }
});

代码示例来源：origin: spring-projects/spring-framework

/**
 * Set the environment properties used to construct the {@code JMXConnectorServer}
 * as {@code java.util.Properties} (String key/value pairs).
 */
public void setEnvironment(@Nullable Properties environment) {
  CollectionUtils.mergePropertiesIntoMap(environment, this.environment);
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Find a single value of one of the given types in the given Collection:
 * searching the Collection for a value of the first type, then
 * searching for a value of the second type, etc.
 * @param collection the collection to search
 * @param types the types to look for, in prioritized order
 * @return a value of one of the given types found if there is a clear match,
 * or {@code null} if none or more than one such value found
 */
@Nullable
public static Object findValueOfType(Collection<?> collection, Class<?>[] types) {
  if (isEmpty(collection) || ObjectUtils.isEmpty(types)) {
    return null;
  }
  for (Class<?> type : types) {
    Object value = findValueOfType(collection, type);
    if (value != null) {
      return value;
    }
  }
  return null;
}

代码示例来源：origin: spring-projects/spring-framework

protected boolean checkDestinationPrefix(@Nullable String destination) {
  if (destination == null || CollectionUtils.isEmpty(this.destinationPrefixes)) {
    return true;
  }
  for (String prefix : this.destinationPrefixes) {
    if (destination.startsWith(prefix)) {
      return true;
    }
  }
  return false;
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Return whether this ModelAndView object is empty,
 * i.e. whether it does not hold any view and does not contain a model.
 */
public boolean isEmpty() {
  return (this.view == null && CollectionUtils.isEmpty(this.model));
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Create a container-managed extended EntityManager proxy.
 * @param emf the EntityManagerFactory to create the EntityManager with.
 * If this implements the EntityManagerFactoryInfo interface, the corresponding
 * JpaDialect and PersistenceUnitInfo will be detected accordingly.
 * @param properties the properties to be passed into the {@code createEntityManager}
 * call (may be {@code null})
 * @param synchronizedWithTransaction whether to automatically join ongoing
 * transactions (according to the JPA 2.1 SynchronizationType rules)
 * @return a container-managed EntityManager that expects container-driven lifecycle
 * management but may opt out of automatic transaction synchronization
 * @since 4.0
 * @see javax.persistence.EntityManagerFactory#createEntityManager(java.util.Map)
 */
public static EntityManager createContainerManagedEntityManager(
    EntityManagerFactory emf, @Nullable Map<?, ?> properties, boolean synchronizedWithTransaction) {
  Assert.notNull(emf, "EntityManagerFactory must not be null");
  if (emf instanceof EntityManagerFactoryInfo) {
    EntityManagerFactoryInfo emfInfo = (EntityManagerFactoryInfo) emf;
    EntityManagerFactory nativeEmf = emfInfo.getNativeEntityManagerFactory();
    EntityManager rawEntityManager = (!CollectionUtils.isEmpty(properties) ?
        nativeEmf.createEntityManager(properties) : nativeEmf.createEntityManager());
    return createProxy(rawEntityManager, emfInfo, true, synchronizedWithTransaction);
  }
  else {
    EntityManager rawEntityManager = (!CollectionUtils.isEmpty(properties) ?
        emf.createEntityManager(properties) : emf.createEntityManager());
    return createProxy(rawEntityManager, null, null, null, null, true, synchronizedWithTransaction);
  }
}

代码示例来源：origin: hs-web/hsweb-framework

@Override
public List<Term> getTerms() {
  List<Term> terms = super.getTerms();
  if (CollectionUtils.isEmpty(terms) && StringUtils.hasText(termExpression)) {
    setTerms(terms = TermExpressionParser.parse(termExpression));
  }
  return terms;
}

代码示例来源：origin: spring-projects/spring-framework

@SuppressWarnings("unchecked")
private boolean safeExtension(HttpServletRequest request, @Nullable String extension) {
  if (!StringUtils.hasText(extension)) {
    return true;
  }
  extension = extension.toLowerCase(Locale.ENGLISH);
  if (this.safeExtensions.contains(extension)) {
    return true;
  }
  String pattern = (String) request.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);
  if (pattern != null && pattern.endsWith("." + extension)) {
    return true;
  }
  if (extension.equals("html")) {
    String name = HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE;
    Set<MediaType> mediaTypes = (Set<MediaType>) request.getAttribute(name);
    if (!CollectionUtils.isEmpty(mediaTypes) && mediaTypes.contains(MediaType.TEXT_HTML)) {
      return true;
    }
  }
  return safeMediaTypesForExtension(new ServletWebRequest(request), extension);
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Writes the given values as hidden fields.
 */
private void writeHiddenFields(@Nullable Map<String, String> hiddenFields) throws JspException {
  if (!CollectionUtils.isEmpty(hiddenFields)) {
    Assert.state(this.tagWriter != null, "No TagWriter set");
    this.tagWriter.appendValue("<div>\n");
    for (String name : hiddenFields.keySet()) {
      this.tagWriter.appendValue("<input type=\"hidden\" ");
      this.tagWriter.appendValue("name=\"" + name + "\" value=\"" + hiddenFields.get(name) + "\" ");
      this.tagWriter.appendValue("/>\n");
    }
    this.tagWriter.appendValue("</div>");
  }
}

代码示例来源：origin: spring-projects/spring-framework

private List<View> getCandidateViews(String viewName, Locale locale, List<MediaType> requestedMediaTypes)
    throws Exception {
  List<View> candidateViews = new ArrayList<>();
  if (this.viewResolvers != null) {
    Assert.state(this.contentNegotiationManager != null, "No ContentNegotiationManager set");
    for (ViewResolver viewResolver : this.viewResolvers) {
      View view = viewResolver.resolveViewName(viewName, locale);
      if (view != null) {
        candidateViews.add(view);
      }
      for (MediaType requestedMediaType : requestedMediaTypes) {
        List<String> extensions = this.contentNegotiationManager.resolveFileExtensions(requestedMediaType);
        for (String extension : extensions) {
          String viewNameWithExtension = viewName + '.' + extension;
          view = viewResolver.resolveViewName(viewNameWithExtension, locale);
          if (view != null) {
            candidateViews.add(view);
          }
        }
      }
    }
  }
  if (!CollectionUtils.isEmpty(this.defaultViews)) {
    candidateViews.addAll(this.defaultViews);
  }
  return candidateViews;
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Convert each {@code HttpRange} into a {@code ResourceRegion}, selecting the
 * appropriate segment of the given {@code Resource} using HTTP Range information.
 * @param ranges the list of ranges
 * @param resource the resource to select the regions from
 * @return the list of regions for the given resource
 * @throws IllegalArgumentException if the sum of all ranges exceeds the
 * resource length.
 * @since 4.3
 */
public static List<ResourceRegion> toResourceRegions(List<HttpRange> ranges, Resource resource) {
  if (CollectionUtils.isEmpty(ranges)) {
    return Collections.emptyList();
  }
  List<ResourceRegion> regions = new ArrayList<>(ranges.size());
  for (HttpRange range : ranges) {
    regions.add(range.toResourceRegion(resource));
  }
  if (ranges.size() > 1) {
    long length = getLengthFor(resource);
    long total = regions.stream().map(ResourceRegion::getCount).reduce(0L, (count, sum) -> sum + count);
    Assert.isTrue(total < length,
        () -> "The sum of all ranges (" + total + ") " +
            "should be less than the resource length (" + length + ")");
  }
  return regions;
}

代码示例来源：origin: spring-projects/spring-framework

@Nullable
private Locale resolveSupportedLocale(@Nullable List<Locale> requestLocales) {
  if (CollectionUtils.isEmpty(requestLocales)) {
    return this.defaultLocale;  // may be null
        if (!StringUtils.hasLength(candidate.getCountry()) &&
            candidate.getLanguage().equals(locale.getLanguage())) {
          languageMatch = candidate;

代码示例来源：origin: spring-projects/spring-framework

/**
 * Create a WebSocketExtension with the given name and parameters.
 * @param name the name of the extension
 * @param parameters the parameters
 */
public WebSocketExtension(String name, @Nullable Map<String, String> parameters) {
  Assert.hasLength(name, "Extension name must not be empty");
  this.name = name;
  if (!CollectionUtils.isEmpty(parameters)) {
    Map<String, String> map = new LinkedCaseInsensitiveMap<>(parameters.size(), Locale.ENGLISH);
    map.putAll(parameters);
    this.parameters = Collections.unmodifiableMap(map);
  }
  else {
    this.parameters = Collections.emptyMap();
  }
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Return a unique result object from the given Collection.
 * <p>Returns {@code null} if 0 result objects found;
 * throws an exception if more than 1 instance found.
 * @param results the result Collection (can be {@code null})
 * @return the unique result object, or {@code null} if none
 * @throws IncorrectResultSizeDataAccessException if more than one
 * result object has been found in the given Collection
 * @see org.springframework.util.CollectionUtils#hasUniqueObject
 */
@Nullable
public static <T> T uniqueResult(@Nullable Collection<T> results) throws IncorrectResultSizeDataAccessException {
  if (CollectionUtils.isEmpty(results)) {
    return null;
  }
  if (!CollectionUtils.hasUniqueObject(results)) {
    throw new IncorrectResultSizeDataAccessException(1, results.size());
  }
  return results.iterator().next();
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Assert that a Map contains entries; that is, it must not be {@code null}
 * and must contain at least one entry.
 * <pre class="code">
 * Assert.notEmpty(map, () -&gt; "The " + mapType + " map must contain entries");
 * </pre>
 * @param map the map to check
 * @param messageSupplier a supplier for the exception message to use if the
 * assertion fails
 * @throws IllegalArgumentException if the map is {@code null} or contains no entries
 * @since 5.0
 */
public static void notEmpty(@Nullable Map<?, ?> map, Supplier<String> messageSupplier) {
  if (CollectionUtils.isEmpty(map)) {
    throw new IllegalArgumentException(nullSafeGet(messageSupplier));
  }
}

代码示例来源：origin: spring-projects/spring-framework

@Override
  public List<String> get(Object key) {
    Assert.isInstanceOf(String.class, key, "Key must be a String-based header name");
    Collection<String> values1 = servletResponse.getHeaders((String) key);
    if (headersWritten) {
      return new ArrayList<>(values1);
    }
    boolean isEmpty1 = CollectionUtils.isEmpty(values1);
    List<String> values2 = super.get(key);
    boolean isEmpty2 = CollectionUtils.isEmpty(values2);
    if (isEmpty1 && isEmpty2) {
      return null;
    }
    List<String> values = new ArrayList<>();
    if (!isEmpty1) {
      values.addAll(values1);
    }
    if (!isEmpty2) {
      values.addAll(values2);
    }
    return values;
  }
}

代码示例来源：origin: spring-projects/spring-framework

/**
   * Create new ServletConfigPropertyValues.
   * @param config the ServletConfig we'll use to take PropertyValues from
   * @param requiredProperties set of property names we need, where
   * we can't accept default values
   * @throws ServletException if any required properties are missing
   */
  public ServletConfigPropertyValues(ServletConfig config, Set<String> requiredProperties)
      throws ServletException {
    Set<String> missingProps = (!CollectionUtils.isEmpty(requiredProperties) ?
        new HashSet<>(requiredProperties) : null);
    Enumeration<String> paramNames = config.getInitParameterNames();
    while (paramNames.hasMoreElements()) {
      String property = paramNames.nextElement();
      Object value = config.getInitParameter(property);
      addPropertyValue(new PropertyValue(property, value));
      if (missingProps != null) {
        missingProps.remove(property);
      }
    }
    // Fail if we are still missing properties.
    if (!CollectionUtils.isEmpty(missingProps)) {
      throw new ServletException(
          "Initialization from ServletConfig for servlet '" + config.getServletName() +
          "' failed; the following required properties were missing: " +
          StringUtils.collectionToDelimitedString(missingProps, ", "));
    }
  }
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Set the environment properties used to construct the {@code JMXConnector}
 * as {@code java.util.Properties} (String key/value pairs).
 */
public void setEnvironment(Properties environment) {
  CollectionUtils.mergePropertiesIntoMap(environment, this.environment);
}

代码示例来源：origin: spring-projects/spring-framework

/**
 * Render the inner '{@code option}' tags using the {@link #optionSource}.
 * @see #doRenderFromCollection(java.util.Collection, TagWriter)
 */
private void renderFromArray(TagWriter tagWriter) throws JspException {
  doRenderFromCollection(CollectionUtils.arrayToList(this.optionSource), tagWriter);
}