/** * Returns an array containing all installed providers that satisfy the specified* selection * criteria, or null if no such providers have been installed. The returned providers are ordered * according to their <a href= "#insertProviderAt(java.security.Provider, int)">preference * order</a>. * * <p>The selection criteria are represented by a map. Each map entry represents a selection * criterion. A provider is selected iff it satisfies all selection criteria. The key for any * entry in such a map must be in one of the following two formats: * * <ul> * <li><i><crypto_service>.<algorithm_or_type></i> * <p>The cryptographic service name must not contain any dots. * <p>The value associated with the key must be an empty string. * <p>A provider satisfies this selection criterion iff the provider implements the * specified algorithm or type for the specified cryptographic service. * <li><i><crypto_service>.<algorithm_or_type> <attribute_name></i> * <p>The cryptographic service name must not contain any dots. There must be one or more * space charaters between the <i><algorithm_or_type></i> and the * <i><attribute_name></i>. * <p>The value associated with the key must be a non-empty string. A provider satisfies * this selection criterion iff the provider implements the specified algorithm or type for * the specified cryptographic service and its implementation meets the constraint expressed * by the specified attribute name/value pair. * </ul> * * <p>See Appendix A in the <a href= "../../../guide/security/CryptoSpec.html#AppA"> Java * Cryptogaphy Architecture API Specification & Reference </a> for information about standard * cryptographic service names, standard algorithm names and standard attribute names. * * @param filter the criteria for selecting providers. The filter is case-insensitive. * @return all the installed providers that satisfy the selection criteria, or null if no such * providers have been installed. * @throws InvalidParameterException if the filter is not in the required format * @throws NullPointerException if filter is null * @see #getProviders(java.lang.String) */ public static Provider[] getProviders(Map<String, String> filter) { // Get all installed providers first. // Then only return those providers who satisfy the selection criteria. Provider[] allProviders = Security.getProviders(); Set keySet = filter.keySet(); LinkedHashSet candidates = new LinkedHashSet(5); // Returns all installed providers // if the selection criteria is null. if ((keySet == null) || (allProviders == null)) { return allProviders; } boolean firstSearch = true; // For each selection criterion, remove providers // which don't satisfy the criterion from the candidate set. for (Iterator ite = keySet.iterator(); ite.hasNext(); ) { String key = (String) ite.next(); String value = (String) filter.get(key); LinkedHashSet newCandidates = getAllQualifyingCandidates(key, value, allProviders); if (firstSearch) { candidates = newCandidates; firstSearch = false; } if ((newCandidates != null) && !newCandidates.isEmpty()) { // For each provider in the candidates set, if it // isn't in the newCandidate set, we should remove // it from the candidate set. for (Iterator cansIte = candidates.iterator(); cansIte.hasNext(); ) { Provider prov = (Provider) cansIte.next(); if (!newCandidates.contains(prov)) { cansIte.remove(); } } } else { candidates = null; break; } } if ((candidates == null) || (candidates.isEmpty())) return null; Object[] candidatesArray = candidates.toArray(); Provider[] result = new Provider[candidatesArray.length]; for (int i = 0; i < result.length; i++) { result[i] = (Provider) candidatesArray[i]; } return result; }