Java tutorial
package com.fasterxml.jackson.dataformat.xml.ser; import java.io.IOException; import javax.xml.namespace.QName; import com.fasterxml.jackson.core.*; import com.fasterxml.jackson.annotation.JsonTypeInfo; import com.fasterxml.jackson.databind.*; import com.fasterxml.jackson.databind.jsontype.TypeSerializer; import com.fasterxml.jackson.databind.ser.BeanPropertyFilter; import com.fasterxml.jackson.databind.ser.BeanPropertyWriter; import com.fasterxml.jackson.databind.ser.BeanSerializer; import com.fasterxml.jackson.databind.ser.impl.ObjectIdWriter; import com.fasterxml.jackson.databind.ser.std.BeanSerializerBase; import com.fasterxml.jackson.databind.util.NameTransformer; import com.fasterxml.jackson.dataformat.xml.util.XmlInfo; /** * Specific sub-class of {@link BeanSerializer} needed to take care * of some xml-specific aspects, such as distinction between attributes * and elements. */ public class XmlBeanSerializer extends BeanSerializer { /** * Marker used for storing associated internal data with {@link BeanPropertyWriter} * instances; to mark instances that are to be written out as attributes. * Created as separate non-interned String to ensure there are no collisions. */ public final static String KEY_XML_INFO = new String("xmlInfo"); /** * Number of attributes to write; these will have been ordered to be the first * properties to write. */ protected final int _attributeCount; /** * Index of "text value" property we have, if any; can have at most * one such property. */ protected final int _textPropertyIndex; /** * Array that contains namespace URIs associated with properties, if any; * null if no namespace definitions have been assigned */ protected final QName[] _xmlNames; public XmlBeanSerializer(BeanSerializerBase src) { super(src); /* Then make sure attributes are sorted before elements, keep track * of how many there are altogether */ int attrCount = 0; for (BeanPropertyWriter bpw : _props) { if (_isAttribute(bpw)) { // Yup: let's build re-ordered list then attrCount = _orderAttributesFirst(_props, _filteredProps); break; } } _attributeCount = attrCount; // And then collect namespace information _xmlNames = new QName[_props.length]; int textIndex = -1; for (int i = 0, len = _props.length; i < len; ++i) { BeanPropertyWriter bpw = _props[i]; XmlInfo info = (XmlInfo) bpw.getInternalSetting(KEY_XML_INFO); String ns = null; if (info != null) { ns = info.getNamespace(); if (textIndex < 0 && info.isText()) { textIndex = i; } } _xmlNames[i] = new QName((ns == null) ? "" : ns, bpw.getName()); } _textPropertyIndex = textIndex; } protected XmlBeanSerializer(XmlBeanSerializer src, ObjectIdWriter objectIdWriter) { super(src, objectIdWriter); _attributeCount = src._attributeCount; _textPropertyIndex = src._textPropertyIndex; _xmlNames = src._xmlNames; } /* /********************************************************** /* Life-cycle: factory methods, fluent factories /********************************************************** */ @Override public JsonSerializer<Object> unwrappingSerializer(NameTransformer unwrapper) { // 19-Feb-2012, tatu: Should support unwrapping for XML too... but not yet done // return new UnwrappingBeanSerializer(this, unwrapper); throw new UnsupportedOperationException("Unwrapping serialization not yet supported for XML"); } @Override public BeanSerializer withObjectIdWriter(ObjectIdWriter objectIdWriter) { return new XmlBeanSerializer(this, objectIdWriter); } /* /********************************************************** /* Overridden serialization methods /********************************************************** */ /** * Main serialization method needs to be overridden to allow XML-specific * extra handling, such as indication of whether to write attributes or * elements. */ @Override protected void serializeFields(Object bean, JsonGenerator jgen0, SerializerProvider provider) throws IOException, JsonGenerationException { // 19-Aug-2013, tatu: During 'convertValue()', need to skip if (!(jgen0 instanceof ToXmlGenerator)) { super.serializeFields(bean, jgen0, provider); return; } final ToXmlGenerator xgen = (ToXmlGenerator) jgen0; final BeanPropertyWriter[] props; // !!! TODO: change to use non-deprecated version in 2.3 if (_filteredProps != null && provider.getActiveView() != null) { props = _filteredProps; } else { props = _props; } final int attrCount = _attributeCount; if (attrCount > 0) { xgen.setNextIsAttribute(true); } final int textIndex = _textPropertyIndex; final QName[] xmlNames = _xmlNames; int i = 0; try { for (final int len = props.length; i < len; ++i) { if (i == attrCount) { xgen.setNextIsAttribute(false); } // also: if this is property to write as text ("unwrap"), need to: if (i == textIndex) { xgen.setNextIsUnwrapped(true); } xgen.setNextName(xmlNames[i]); BeanPropertyWriter prop = props[i]; if (prop != null) { // can have nulls in filtered list prop.serializeAsField(bean, xgen, provider); } } if (_anyGetterWriter != null) { _anyGetterWriter.getAndSerialize(bean, xgen, provider); } } catch (Exception e) { String name = (i == props.length) ? "[anySetter]" : props[i].getName(); wrapAndThrow(provider, e, bean, name); } catch (StackOverflowError e) { // Bit tricky, can't do more calls as stack is full; so: JsonMappingException mapE = new JsonMappingException("Infinite recursion (StackOverflowError)"); String name = (i == props.length) ? "[anySetter]" : props[i].getName(); mapE.prependPath(new JsonMappingException.Reference(bean, name)); throw mapE; } } @Override protected void serializeFieldsFiltered(Object bean, JsonGenerator jgen0, SerializerProvider provider) throws IOException, JsonGenerationException { // 19-Aug-2013, tatu: During 'convertValue()', need to skip if (!(jgen0 instanceof ToXmlGenerator)) { super.serializeFieldsFiltered(bean, jgen0, provider); return; } final ToXmlGenerator xgen = (ToXmlGenerator) jgen0; final BeanPropertyWriter[] props; // !!! TODO: change to use non-deprecated version in 2.3 if (_filteredProps != null && provider.getActiveView() != null) { props = _filteredProps; } else { props = _props; } final BeanPropertyFilter filter = findFilter(provider); // better also allow missing filter actually.. if (filter == null) { serializeFields(bean, jgen0, provider); return; } final int attrCount = _attributeCount; if (attrCount > 0) { xgen.setNextIsAttribute(true); } final int textIndex = _textPropertyIndex; final QName[] xmlNames = _xmlNames; int i = 0; try { for (final int len = props.length; i < len; ++i) { if (i == attrCount) { xgen.setNextIsAttribute(false); } // also: if this is property to write as text ("unwrap"), need to: if (i == textIndex) { xgen.setNextIsUnwrapped(true); } xgen.setNextName(xmlNames[i]); BeanPropertyWriter prop = props[i]; if (prop != null) { // can have nulls in filtered list filter.serializeAsField(bean, xgen, provider, prop); } } if (_anyGetterWriter != null) { _anyGetterWriter.getAndSerialize(bean, xgen, provider); } } catch (Exception e) { String name = (i == props.length) ? "[anySetter]" : props[i].getName(); wrapAndThrow(provider, e, bean, name); } catch (StackOverflowError e) { JsonMappingException mapE = new JsonMappingException("Infinite recursion (StackOverflowError)", e); String name = (i == props.length) ? "[anySetter]" : props[i].getName(); mapE.prependPath(new JsonMappingException.Reference(bean, name)); throw mapE; } } @Override public void serializeWithType(Object bean, JsonGenerator jgen, SerializerProvider provider, TypeSerializer typeSer) throws IOException, JsonGenerationException { /* Ok: let's serialize type id as attribute, but if (and only if!) * we are using AS_PROPERTY */ if (typeSer.getTypeInclusion() == JsonTypeInfo.As.PROPERTY) { ToXmlGenerator xgen = (ToXmlGenerator) jgen; xgen.setNextIsAttribute(true); super.serializeWithType(bean, jgen, provider, typeSer); if (_attributeCount == 0) { // if no attributes, need to reset xgen.setNextIsAttribute(false); } } else { super.serializeWithType(bean, jgen, provider, typeSer); } } /* /********************************************************** /* Helper methods /********************************************************** */ protected static boolean _isAttribute(BeanPropertyWriter bpw) { XmlInfo info = (XmlInfo) bpw.getInternalSetting(KEY_XML_INFO); return (info != null) && info.isAttribute(); } /** * Method for re-sorting lists of bean properties such that attributes are strictly * written before elements. */ protected static int _orderAttributesFirst(BeanPropertyWriter[] properties, BeanPropertyWriter[] filteredProperties) { int attrCount = 0; for (int i = 0, len = properties.length; i < len; ++i) { BeanPropertyWriter bpw = properties[i]; if (!_isAttribute(bpw)) { continue; } // Swap if attribute and there are preceding elements: if (attrCount < i) { properties[i] = properties[attrCount]; properties[attrCount] = bpw; if (filteredProperties != null) { BeanPropertyWriter fbpw = filteredProperties[i]; filteredProperties[i] = filteredProperties[attrCount]; filteredProperties[attrCount] = fbpw; } } ++attrCount; } return attrCount; } }