Add SimpleTokenWriteContext

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/core/util/SimpleTokenWriteContext.java

@@ -0,0 +1,198 @@
+package com.fasterxml.jackson.core.util;
+
+import com.fasterxml.jackson.core.*;
+import com.fasterxml.jackson.core.json.DupDetector;
+
+/**
+ * Basic implementation of {@code TokenStreamContext} useful for most
+ * format backends (with notable exception of JSON that needs bit more
+ * advanced state).
+ *
+ * @since 3.0
+ */
+public final class SimpleTokenWriteContext extends TokenStreamContext
+{
+    /**
+     * Parent context for this context; null for root context.
+     */
+    protected final SimpleTokenWriteContext _parent;
+
+    // // // Optional duplicate detection
+
+    protected DupDetector _dups;
+
+    /*
+    /**********************************************************
+    /* Simple instance reuse slots; speed up things a bit (10-15%)
+    /* for docs with lots of small arrays/objects
+    /**********************************************************
+     */
+
+    protected SimpleTokenWriteContext _childToRecycle;
+
+    /*
+    /**********************************************************
+    /* Location/state information (minus source reference)
+    /**********************************************************
+     */
+
+    /**
+     * Name of the field of which value is to be written; only
+     * used for OBJECT contexts
+     */
+    protected String _currentName;
+
+    protected Object _currentValue;
+
+    /**
+     * Marker used to indicate that we just wrote a field name
+     * and now expect a value to write
+     */
+    protected boolean _gotFieldId;
+
+    /*
+    /**********************************************************************
+    /* Life-cycle
+    /**********************************************************************
+     */
+
+    protected SimpleTokenWriteContext(int type, SimpleTokenWriteContext parent, DupDetector dups,
+            Object currentValue) {
+        super();
+        _type = type;
+        _parent = parent;
+        _dups = dups;
+        _index = -1;
+        _currentValue = currentValue;
+    }
+
+    private SimpleTokenWriteContext reset(int type, Object currentValue) {
+        _type = type;
+        _index = -1;
+        // as long as _gotFieldId false, current name/id can be left as-is
+        _gotFieldId = false;
+        _currentValue = currentValue;
+        if (_dups != null) { _dups.reset(); }
+        return this;
+    }
+
+    public SimpleTokenWriteContext withDupDetector(DupDetector dups) {
+        _dups = dups;
+        return this;
+    }
+
+    @Override
+    public Object getCurrentValue() {
+        return _currentValue;
+    }
+
+    @Override
+    public void setCurrentValue(Object v) {
+        _currentValue = v;
+    }
+
+    /*
+    /**********************************************************************
+    /* Factory methods
+    /**********************************************************************
+     */
+
+    public static SimpleTokenWriteContext createRootContext(DupDetector dd) {
+        return new SimpleTokenWriteContext(TYPE_ROOT, null, dd, null);
+    }
+
+    public SimpleTokenWriteContext createChildArrayContext(Object currentValue) {
+        SimpleTokenWriteContext ctxt = _childToRecycle;
+        if (ctxt == null) {
+            _childToRecycle = ctxt = new SimpleTokenWriteContext(TYPE_ARRAY, this,
+                    (_dups == null) ? null : _dups.child(), currentValue);
+            return ctxt;
+        }
+        return ctxt.reset(TYPE_ARRAY, currentValue);
+    }
+
+    public SimpleTokenWriteContext createChildObjectContext(Object currentValue) {
+        SimpleTokenWriteContext ctxt = _childToRecycle;
+        if (ctxt == null) {
+            _childToRecycle = ctxt = new SimpleTokenWriteContext(TYPE_OBJECT, this,
+                    (_dups == null) ? null : _dups.child(), currentValue);
+            return ctxt;
+        }
+        return ctxt.reset(TYPE_OBJECT, currentValue);
+    }
+
+    /*
+    /**********************************************************************
+    /* Accessors
+    /**********************************************************************
+     */
+    
+    @Override public final SimpleTokenWriteContext getParent() { return _parent; }
+    @Override public final String currentName() {
+        if (_gotFieldId) {
+            return _currentName;
+        }
+        return null;
+    }
+
+    @Override public boolean hasCurrentName() { return _gotFieldId; }
+
+    /**
+     * Method that can be used to both clear the accumulated references
+     * (specifically value set with {@link #setCurrentValue(Object)})
+     * that should not be retained, and returns parent (as would
+     * {@link #getParent()} do). Typically called when closing the active
+     * context when encountering {@link JsonToken#END_ARRAY} or
+     * {@link JsonToken#END_OBJECT}.
+     */
+    public SimpleTokenWriteContext clearAndGetParent() {
+        _currentValue = null;
+        // could also clear the current name, but seems cheap enough to leave?
+        return _parent;
+    }
+
+    public DupDetector getDupDetector() {
+        return _dups;
+    }
+
+    /*
+    /**********************************************************************
+    /* State changing
+    /**********************************************************************
+     */
+    
+    /**
+     * Method that writer is to call before it writes a field name.
+     *
+     * @return Ok if name writing should proceed
+     */
+    public boolean writeFieldName(String name) throws JsonProcessingException {
+        if ((_type != TYPE_OBJECT) || _gotFieldId) {
+            return false;
+        }
+        _gotFieldId = true;
+        _currentName = name;
+        if (_dups != null) { _checkDup(_dups, name); }
+        return true;
+    }
+
+    private final void _checkDup(DupDetector dd, String name) throws JsonProcessingException {
+        if (dd.isDup(name)) {
+            Object src = dd.getSource();
+            throw new JsonGenerationException("Duplicate field '"+name+"'",
+                    ((src instanceof JsonGenerator) ? ((JsonGenerator) src) : null));
+        }
+    }
+    
+    public boolean writeValue() {
+        // Only limitation is with OBJECTs:
+        if (_type == TYPE_OBJECT) {
+            if (!_gotFieldId) {
+                return false;
+            }
+            _gotFieldId = false;
+        }
+        ++_index;
+        return true;
+    }
+}