spring YamlProcessor 源码
spring YamlProcessor 代码
文件路径：/spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java
/*
* Copyright 2002-2022 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.beans.factory.config;
import java.io.IOException;
import java.io.Reader;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;
import java.util.stream.Collectors;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.yaml.snakeyaml.DumperOptions;
import org.yaml.snakeyaml.LoaderOptions;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.constructor.Constructor;
import org.yaml.snakeyaml.reader.UnicodeReader;
import org.yaml.snakeyaml.representer.Representer;
import org.springframework.core.CollectionFactory;
import org.springframework.core.io.Resource;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
/**
* Base class for YAML factories.
*
* <p>Requires SnakeYAML 1.18 or higher, as of Spring Framework 5.0.6.
*
* @author Dave Syer
* @author Juergen Hoeller
* @author Sam Brannen
* @author Brian Clozel
* @since 4.1
*/
public abstract class YamlProcessor {
private final Log logger = LogFactory.getLog(getClass());
private ResolutionMethod resolutionMethod = ResolutionMethod.OVERRIDE;
private Resource[] resources = new Resource[0];
private List<DocumentMatcher> documentMatchers = Collections.emptyList();
private boolean matchDefault = true;
private Set<String> supportedTypes = Collections.emptySet();
/**
* A map of document matchers allowing callers to selectively use only
* some of the documents in a YAML resource. In YAML documents are
* separated by {@code ---} lines, and each document is converted
* to properties before the match is made. E.g.
* <pre class="code">
* environment: dev
* url: https://dev.bar.com
* name: Developer Setup
* ---
* environment: prod
* url:https://foo.bar.com
* name: My Cool App
* </pre>
* when mapped with
* <pre class="code">
* setDocumentMatchers(properties ->
* ("prod".equals(properties.getProperty("environment")) ? MatchStatus.FOUND : MatchStatus.NOT_FOUND));
* </pre>
* would end up as
* <pre class="code">
* environment=prod
* url=https://foo.bar.com
* name=My Cool App
* </pre>
*/
public void setDocumentMatchers(DocumentMatcher... matchers) {
this.documentMatchers = List.of(matchers);
}
/**
* Flag indicating that a document for which all the
* {@link #setDocumentMatchers(DocumentMatcher...) document matchers} abstain will
* nevertheless match. Default is {@code true}.
*/
public void setMatchDefault(boolean matchDefault) {
this.matchDefault = matchDefault;
}
/**
* Method to use for resolving resources. Each resource will be converted to a Map,
* so this property is used to decide which map entries to keep in the final output
* from this factory. Default is {@link ResolutionMethod#OVERRIDE}.
*/
public void setResolutionMethod(ResolutionMethod resolutionMethod) {
Assert.notNull(resolutionMethod, "ResolutionMethod must not be null");
this.resolutionMethod = resolutionMethod;
}
/**
* Set locations of YAML {@link Resource resources} to be loaded.
* @see ResolutionMethod
*/
public void setResources(Resource... resources) {
this.resources = resources;
}
/**
* Set the supported types that can be loaded from YAML documents.
* <p>If no supported types are configured, only Java standard classes
* (as defined in {@link org.yaml.snakeyaml.constructor.SafeConstructor})
* encountered in YAML documents will be supported.
* If an unsupported type is encountered, an {@link IllegalStateException}
* will be thrown when the corresponding YAML node is processed.
* @param supportedTypes the supported types, or an empty array to clear the
* supported types
* @since 5.1.16
* @see #createYaml()
*/
public void setSupportedTypes(Class<?>... supportedTypes) {
if (ObjectUtils.isEmpty(supportedTypes)) {
this.supportedTypes = Collections.emptySet();
}
else {
Assert.noNullElements(supportedTypes, "'supportedTypes' must not contain null elements");
this.supportedTypes = Arrays.stream(supportedTypes).map(Class::getName)
.collect(Collectors.toUnmodifiableSet());
}
}
/**
* Provide an opportunity for subclasses to process the Yaml parsed from the supplied
* resources. Each resource is parsed in turn and the documents inside checked against
* the {@link #setDocumentMatchers(DocumentMatcher...) matchers}. If a document
* matches it is passed into the callback, along with its representation as Properties.
* Depending on the {@link #setResolutionMethod(ResolutionMethod)} not all the
* documents will be parsed.
* @param callback a callback to delegate to once matching documents are found
* @see #createYaml()
*/
protected void process(MatchCallback callback) {
Yaml yaml = createYaml();
for (Resource resource : this.resources) {
boolean found = process(callback, yaml, resource);
if (this.resolutionMethod == ResolutionMethod.FIRST_FOUND && found) {
return;
}
}
}
/**
* Create the {@link Yaml} instance to use.
* <p>The default implementation sets the "allowDuplicateKeys" flag to {@code false},
* enabling built-in duplicate key handling in SnakeYAML 1.18+.
* <p>As of Spring Framework 5.1.16, if custom {@linkplain #setSupportedTypes
* supported types} have been configured, the default implementation creates
* a {@code Yaml} instance that filters out unsupported types encountered in
* YAML documents. If an unsupported type is encountered, an
* {@link IllegalStateException} will be thrown when the node is processed.
* @see LoaderOptions#setAllowDuplicateKeys(boolean)
*/
protected Yaml createYaml() {
LoaderOptions loaderOptions = new LoaderOptions();
loaderOptions.setAllowDuplicateKeys(false);
return new Yaml(new FilteringConstructor(loaderOptions), new Representer(),
new DumperOptions(), loaderOptions);
}
private boolean process(MatchCallback callback, Yaml yaml, Resource resource) {
int count = 0;
try {
if (logger.isDebugEnabled()) {
logger.debug("Loading from YAML: " + resource);
}
try (Reader reader = new UnicodeReader(resource.getInputStream())) {
for (Object object : yaml.loadAll(reader)) {
if (object != null && process(asMap(object), callback)) {
count++;
if (this.resolutionMethod == ResolutionMethod.FIRST_FOUND) {
break;
}
}
}
if (logger.isDebugEnabled()) {
logger.debug("Loaded " + count + " document" + (count > 1 ? "s" : "") +
" from YAML resource: " + resource);
}
}
}
catch (IOException ex) {
handleProcessError(resource, ex);
}
return (count > 0);
}
private void handleProcessError(Resource resource, IOException ex) {
if (this.resolutionMethod != ResolutionMethod.FIRST_FOUND &&
this.resolutionMethod != ResolutionMethod.OVERRIDE_AND_IGNORE) {
throw new IllegalStateException(ex);
}
if (logger.isWarnEnabled()) {
logger.warn("Could not load map from " + resource + ": " + ex.getMessage());
}
}
@SuppressWarnings("unchecked")
private Map<String, Object> asMap(Object object) {
// YAML can have numbers as keys
Map<String, Object> result = new LinkedHashMap<>();
if (!(object instanceof Map)) {
// A document can be a text literal
result.put("document", object);
return result;
}
Map<Object, Object> map = (Map<Object, Object>) object;
map.forEach((key, value) -> {
if (value instanceof Map) {
value = asMap(value);
}
if (key instanceof CharSequence) {
result.put(key.toString(), value);
}
else {
// It has to be a map key in this case
result.put("[" + key.toString() + "]", value);
}
});
return result;
}
private boolean process(Map<String, Object> map, MatchCallback callback) {
Properties properties = CollectionFactory.createStringAdaptingProperties();
properties.putAll(getFlattenedMap(map));
if (this.documentMatchers.isEmpty()) {
if (logger.isDebugEnabled()) {
logger.debug("Merging document (no matchers set): " + map);
}
callback.process(properties, map);
return true;
}
MatchStatus result = MatchStatus.ABSTAIN;
for (DocumentMatcher matcher : this.documentMatchers) {
MatchStatus match = matcher.matches(properties);
result = MatchStatus.getMostSpecific(match, result);
if (match == MatchStatus.FOUND) {
if (logger.isDebugEnabled()) {
logger.debug("Matched document with document matcher: " + properties);
}
callback.process(properties, map);
return true;
}
}
if (result == MatchStatus.ABSTAIN && this.matchDefault) {
if (logger.isDebugEnabled()) {
logger.debug("Matched document with default matcher: " + map);
}
callback.process(properties, map);
return true;
}
if (logger.isDebugEnabled()) {
logger.debug("Unmatched document: " + map);
}
return false;
}
/**
* Return a flattened version of the given map, recursively following any nested Map
* or Collection values. Entries from the resulting map retain the same order as the
* source. When called with the Map from a {@link MatchCallback} the result will
* contain the same values as the {@link MatchCallback} Properties.
* @param source the source map
* @return a flattened map
* @since 4.1.3
*/
protected final Map<String, Object> getFlattenedMap(Map<String, Object> source) {
Map<String, Object> result = new LinkedHashMap<>();
buildFlattenedMap(result, source, null);
return result;
}
private void buildFlattenedMap(Map<String, Object> result, Map<String, Object> source, @Nullable String path) {
source.forEach((key, value) -> {
if (StringUtils.hasText(path)) {
if (key.startsWith("[")) {
key = path + key;
}
else {
key = path + '.' + key;
}
}
if (value instanceof String) {
result.put(key, value);
}
else if (value instanceof Map) {
// Need a compound key
@SuppressWarnings("unchecked")
Map<String, Object> map = (Map<String, Object>) value;
buildFlattenedMap(result, map, key);
}
else if (value instanceof Collection) {
// Need a compound key
@SuppressWarnings("unchecked")
Collection<Object> collection = (Collection<Object>) value;
if (collection.isEmpty()) {
result.put(key, "");
}
else {
int count = 0;
for (Object object : collection) {
buildFlattenedMap(result, Collections.singletonMap(
"[" + (count++) + "]", object), key);
}
}
}
else {
result.put(key, (value != null ? value : ""));
}
});
}
/**
* Callback interface used to process the YAML parsing results.
*/
@FunctionalInterface
public interface MatchCallback {
/**
* Process the given representation of the parsing results.
* @param properties the properties to process (as a flattened
* representation with indexed keys in case of a collection or map)
* @param map the result map (preserving the original value structure
* in the YAML document)
*/
void process(Properties properties, Map<String, Object> map);
}
/**
* Strategy interface used to test if properties match.
*/
@FunctionalInterface
public interface DocumentMatcher {
/**
* Test if the given properties match.
* @param properties the properties to test
* @return the status of the match
*/
MatchStatus matches(Properties properties);
}
/**
* Status returned from {@link DocumentMatcher#matches(java.util.Properties)}.
*/
public enum MatchStatus {
/**
* A match was found.
*/
FOUND,
/**
* No match was found.
*/
NOT_FOUND,
/**
* The matcher should not be considered.
*/
ABSTAIN;
/**
* Compare two {@link MatchStatus} items, returning the most specific status.
*/
public static MatchStatus getMostSpecific(MatchStatus a, MatchStatus b) {
return (a.ordinal() < b.ordinal() ? a : b);
}
}
/**
* Method to use for resolving resources.
*/
public enum ResolutionMethod {
/**
* Replace values from earlier in the list.
*/
OVERRIDE,
/**
* Replace values from earlier in the list, ignoring any failures.
*/
OVERRIDE_AND_IGNORE,
/**
* Take the first resource in the list that exists and use just that.
*/
FIRST_FOUND
}
/**
* {@link Constructor} that supports filtering of unsupported types.
* <p>If an unsupported type is encountered in a YAML document, an
* {@link IllegalStateException} will be thrown from {@link #getClassForName}.
*/
private class FilteringConstructor extends Constructor {
FilteringConstructor(LoaderOptions loaderOptions) {
super(loaderOptions);
}
@Override
protected Class<?> getClassForName(String name) throws ClassNotFoundException {
Assert.state(YamlProcessor.this.supportedTypes.contains(name),
() -> "Unsupported type encountered in YAML document: " + name);
return super.getClassForName(name);
}
}
}
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