Keep tags order using SnakeYAML - json

Question

I'm trying to translate yaml files to json, but the translation re-orders the tags...
Ex, YAML source:
zzzz:
b: 456
a: dfff
aa:
s10: "dddz"
s3: eeee
bbb:
- b1
- a2
snakeYAML produces:
{
"aa": {
"s3": "eeee",
"s10":"dddz"
},
"bbb":[
"b1",
"a2"
],
"zzzz": {
"a": "dfff",
"b":456
}
}

Answer 1

Create following class in your code, this is a tweaked version from the SnakeYAML source that uses LinkedHashMap and LinkedHashSet that keep the insertion order instead of TreeMap and TreeSet which auto-sort them.
import java.beans.FeatureDescriptor;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.*;
import org.yaml.snakeyaml.error.YAMLException;
import org.yaml.snakeyaml.introspector.*;
import org.yaml.snakeyaml.util.PlatformFeatureDetector;
public class CustomPropertyUtils extends PropertyUtils {
private final Map<Class<?>, Map<String, Property>> propertiesCache = new HashMap<Class<?>, Map<String, Property>>();
private final Map<Class<?>, Set<Property>> readableProperties = new HashMap<Class<?>, Set<Property>>();
private BeanAccess beanAccess = BeanAccess.DEFAULT;
private boolean allowReadOnlyProperties = false;
private boolean skipMissingProperties = false;
private PlatformFeatureDetector platformFeatureDetector;
public CustomPropertyUtils() {
this(new PlatformFeatureDetector());
}
CustomPropertyUtils(PlatformFeatureDetector platformFeatureDetector) {
this.platformFeatureDetector = platformFeatureDetector;
/*
* Android lacks much of java.beans (including the Introspector class, used here), because java.beans classes tend to rely on java.awt, which isn't
* supported in the Android SDK. That means we have to fall back on FIELD access only when SnakeYAML is running on the Android Runtime.
*/
if (platformFeatureDetector.isRunningOnAndroid()) {
beanAccess = BeanAccess.FIELD;
}
}
protected Map<String, Property> getPropertiesMap(Class<?> type, BeanAccess bAccess) {
if (propertiesCache.containsKey(type)) {
return propertiesCache.get(type);
}
Map<String, Property> properties = new LinkedHashMap<String, Property>();
boolean inaccessableFieldsExist = false;
switch (bAccess) {
case FIELD:
for (Class<?> c = type; c != null; c = c.getSuperclass()) {
for (Field field : c.getDeclaredFields()) {
int modifiers = field.getModifiers();
if (!Modifier.isStatic(modifiers) && !Modifier.isTransient(modifiers)
&& !properties.containsKey(field.getName())) {
properties.put(field.getName(), new FieldProperty(field));
}
}
}
break;
default:
// add JavaBean properties
try {
for (PropertyDescriptor property : Introspector.getBeanInfo(type)
.getPropertyDescriptors()) {
Method readMethod = property.getReadMethod();
if ((readMethod == null || !readMethod.getName().equals("getClass"))
&& !isTransient(property)) {
properties.put(property.getName(), new MethodProperty(property));
}
}
} catch (IntrospectionException e) {
throw new YAMLException(e);
}
// add public fields
for (Class<?> c = type; c != null; c = c.getSuperclass()) {
for (Field field : c.getDeclaredFields()) {
int modifiers = field.getModifiers();
if (!Modifier.isStatic(modifiers) && !Modifier.isTransient(modifiers)) {
if (Modifier.isPublic(modifiers)) {
properties.put(field.getName(), new FieldProperty(field));
} else {
inaccessableFieldsExist = true;
}
}
}
}
break;
}
if (properties.isEmpty() && inaccessableFieldsExist) {
throw new YAMLException("No JavaBean properties found in " + type.getName());
}
System.out.println(properties);
propertiesCache.put(type, properties);
return properties;
}
private static final String TRANSIENT = "transient";
private boolean isTransient(FeatureDescriptor fd) {
return Boolean.TRUE.equals(fd.getValue(TRANSIENT));
}
public Set<Property> getProperties(Class<? extends Object> type) {
return getProperties(type, beanAccess);
}
public Set<Property> getProperties(Class<? extends Object> type, BeanAccess bAccess) {
if (readableProperties.containsKey(type)) {
return readableProperties.get(type);
}
Set<Property> properties = createPropertySet(type, bAccess);
readableProperties.put(type, properties);
return properties;
}
protected Set<Property> createPropertySet(Class<? extends Object> type, BeanAccess bAccess) {
Set<Property> properties = new LinkedHashSet<>();
Collection<Property> props = getPropertiesMap(type, bAccess).values();
for (Property property : props) {
if (property.isReadable() && (allowReadOnlyProperties || property.isWritable())) {
properties.add(property);
}
}
return properties;
}
public Property getProperty(Class<? extends Object> type, String name) {
return getProperty(type, name, beanAccess);
}
public Property getProperty(Class<? extends Object> type, String name, BeanAccess bAccess) {
Map<String, Property> properties = getPropertiesMap(type, bAccess);
Property property = properties.get(name);
if (property == null && skipMissingProperties) {
property = new MissingProperty(name);
}
if (property == null) {
throw new YAMLException(
"Unable to find property '" + name + "' on class: " + type.getName());
}
return property;
}
public void setBeanAccess(BeanAccess beanAccess) {
if (platformFeatureDetector.isRunningOnAndroid() && beanAccess != BeanAccess.FIELD) {
throw new IllegalArgumentException(
"JVM is Android - only BeanAccess.FIELD is available");
}
if (this.beanAccess != beanAccess) {
this.beanAccess = beanAccess;
propertiesCache.clear();
readableProperties.clear();
}
}
public void setAllowReadOnlyProperties(boolean allowReadOnlyProperties) {
if (this.allowReadOnlyProperties != allowReadOnlyProperties) {
this.allowReadOnlyProperties = allowReadOnlyProperties;
readableProperties.clear();
}
}
public boolean isAllowReadOnlyProperties() {
return allowReadOnlyProperties;
}
/**
* Skip properties that are missing during deserialization of YAML to a Java
* object. The default is false.
*
* #param skipMissingProperties
* true if missing properties should be skipped, false otherwise.
*/
public void setSkipMissingProperties(boolean skipMissingProperties) {
if (this.skipMissingProperties != skipMissingProperties) {
this.skipMissingProperties = skipMissingProperties;
readableProperties.clear();
}
}
public boolean isSkipMissingProperties() {
return skipMissingProperties;
}
}
Then, create your Yaml instance like this:
DumperOptions options = new DumperOptions();
CustomPropertyUtils customPropertyUtils = new CustomPropertyUtils();
Representer customRepresenter = new Representer();
customRepresenter.setPropertyUtils(customPropertyUtils);
Yaml yaml = new Yaml(customRepresenter, options);
Profit!

Answer 2

The keeping of property order depends on java implementation and is not guaranteed.
In order to control the yaml generation you will need to implement your CustomRepresenter overriding the getProperties , see the example below:
package io.github.rockitconsulting.test.rockitizer.configuration;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import org.yaml.snakeyaml.DumperOptions;
import org.yaml.snakeyaml.introspector.Property;
import org.yaml.snakeyaml.representer.Representer;
/**
* Custom implementation of {#link Representer} and {#link Comparator}
* to keep the needed order of javabean properties of model classes,
* thus generating the understandable yaml
*
*/
public class ConfigurationModelRepresenter extends Representer {
public ConfigurationModelRepresenter() {
super();
}
public ConfigurationModelRepresenter(DumperOptions options) {
super(options);
}
protected Set<Property> getProperties(Class<? extends Object> type) {
Set<Property> propertySet;
if (typeDefinitions.containsKey(type)) {
propertySet = typeDefinitions.get(type).getProperties();
}
propertySet = getPropertyUtils().getProperties(type);
List<Property> propsList = new ArrayList<>(propertySet);
Collections.sort(propsList, new BeanPropertyComparator());
return new LinkedHashSet<>(propsList);
}
class BeanPropertyComparator implements Comparator<Property> {
public int compare(Property p1, Property p2) {
if (p1.getType().getCanonicalName().contains("util") && !p2.getType().getCanonicalName().contains("util")) {
return 1;
} else if(p2.getName().endsWith("Name")|| p2.getName().equalsIgnoreCase("name")) {
return 1;
} else {
return -1;
} // returning 0 would merge keys
}
}
}
The below snippet shows the usage of the newly created class to generate the yaml structure:
DumperOptions options = new DumperOptions();
ConfigurationModelRepresenter customRepresenter = new ConfigurationModelRepresenter();
Yaml yaml = new Yaml(customRepresenter, options);
StringWriter writer = new StringWriter();
yaml.dump(suite, writer);
FileWriter fw = new FileWriter(rootPathTestSrc + "config_gen.yml", false);
fw.write(writer.toString());
fw.close();
This approach is much cleaner, comparing to the one suggested above.