Struts源码之OgnlValueStack

public class OgnlValueStack implements Serializable, ValueStack, ClearableValueStack, MemberAccessValueStack {

public static final String THROW_EXCEPTION_ON_FAILURE = OgnlValueStack.class.getName() + ".throwExceptionOnFailure";

private static final long serialVersionUID = 370737852934925530L;

private static final String MAP_IDENTIFIER_KEY = "com.opensymphony.xwork2.util.OgnlValueStack.MAP_IDENTIFIER_KEY";
private static final Logger LOG = LoggerFactory.getLogger(OgnlValueStack.class);

CompoundRoot root;
transient Map<String, Object> context;
Class defaultType;
Map<Object, Object> overrides;
transient OgnlUtil ognlUtil;
transient SecurityMemberAccess securityMemberAccess;

private boolean devMode;
private boolean logMissingProperties;

protected OgnlValueStack(XWorkConverter xworkConverter, CompoundRootAccessor accessor, TextProvider prov, boolean allowStaticAccess) {
setRoot(xworkConverter, accessor, new CompoundRoot(), allowStaticAccess);
push(prov);
}

protected OgnlValueStack(ValueStack vs, XWorkConverter xworkConverter, CompoundRootAccessor accessor, boolean allowStaticAccess) {
setRoot(xworkConverter, accessor, new CompoundRoot(vs.getRoot()), allowStaticAccess);
}

@Inject
public void setOgnlUtil(OgnlUtil ognlUtil) {
this.ognlUtil = ognlUtil;
}

protected void setRoot(XWorkConverter xworkConverter, CompoundRootAccessor accessor, CompoundRoot compoundRoot,
boolean allowStaticMethodAccess) {
this.root = compoundRoot;
this.securityMemberAccess = new SecurityMemberAccess(allowStaticMethodAccess);
this.context = Ognl.createDefaultContext(this.root, accessor, new OgnlTypeConverterWrapper(xworkConverter), securityMemberAccess);
context.put(VALUE_STACK, this);
Ognl.setClassResolver(context, accessor);
((OgnlContext) context).setTraceEvaluations(false);
((OgnlContext) context).setKeepLastEvaluation(false);
}

@Inject(XWorkConstants.DEV_MODE)
public void setDevMode(String mode) {
devMode = "true".equalsIgnoreCase(mode);
}

@Inject(value = "logMissingProperties", required = false)
public void setLogMissingProperties(String logMissingProperties) {
this.logMissingProperties = "true".equalsIgnoreCase(logMissingProperties);
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#getContext()
*/
public Map<String, Object> getContext() {
return context;
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#setDefaultType(java.lang.Class)
*/
public void setDefaultType(Class defaultType) {
this.defaultType = defaultType;
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#setExprOverrides(java.util.Map)
*/
public void setExprOverrides(Map<Object, Object> overrides) {
if (this.overrides == null) {
this.overrides = overrides;
} else {
this.overrides.putAll(overrides);
}
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#getExprOverrides()
*/
public Map<Object, Object> getExprOverrides() {
return this.overrides;
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#getRoot()
*/
public CompoundRoot getRoot() {
return root;
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#setParameter(String, Object)
*/
public void setParameter(String expr, Object value) {
setValue(expr, value, devMode, false);
}

/**

/**
* @see com.opensymphony.xwork2.util.ValueStack#setValue(java.lang.String, java.lang.Object)
*/
public void setValue(String expr, Object value) {
setValue(expr, value, devMode);
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#setValue(java.lang.String, java.lang.Object, boolean)
*/
public void setValue(String expr, Object value, boolean throwExceptionOnFailure) {
setValue(expr, value, throwExceptionOnFailure, true);
}

private void setValue(String expr, Object value, boolean throwExceptionOnFailure, boolean evalExpression) {
Map<String, Object> context = getContext();
try {
trySetValue(expr, value, throwExceptionOnFailure, context, evalExpression);
} catch (OgnlException e) {
handleOgnlException(expr, value, throwExceptionOnFailure, e);
} catch (RuntimeException re) { //XW-281
handleRuntimeException(expr, value, throwExceptionOnFailure, re);
} finally {
cleanUpContext(context);
}
}

private void trySetValue(String expr, Object value, boolean throwExceptionOnFailure, Map<String, Object> context, boolean evalExpression) throws OgnlException {
context.put(XWorkConverter.CONVERSION_PROPERTY_FULLNAME, expr);
context.put(REPORT_ERRORS_ON_NO_PROP, (throwExceptionOnFailure) ? Boolean.TRUE : Boolean.FALSE);
ognlUtil.setValue(expr, context, root, value, evalExpression);
}

private void cleanUpContext(Map<String, Object> context) {
ReflectionContextState.clear(context);
context.remove(XWorkConverter.CONVERSION_PROPERTY_FULLNAME);
context.remove(REPORT_ERRORS_ON_NO_PROP);
}

private void handleRuntimeException(String expr, Object value, boolean throwExceptionOnFailure, RuntimeException re) {
if (throwExceptionOnFailure) {
String message = ErrorMessageBuilder.create()
.errorSettingExpressionWithValue(expr, value)
.build();
throw new XWorkException(message, re);
} else {
if (LOG.isWarnEnabled()) {
LOG.warn("Error setting value", re);
}
}
}

private void handleOgnlException(String expr, Object value, boolean throwExceptionOnFailure, OgnlException e) {
String msg = "Error setting expression '" + expr + "' with value '" + value + "'";
if (LOG.isWarnEnabled()) {
LOG.warn(msg, e);
}
if (throwExceptionOnFailure) {
throw new XWorkException(msg, e);
}
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#findString(java.lang.String)
*/
public String findString(String expr) {
return (String) findValue(expr, String.class);
}

public String findString(String expr, boolean throwExceptionOnFailure) {
return (String) findValue(expr, String.class, throwExceptionOnFailure);
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#findValue(java.lang.String)
*/
public Object findValue(String expr, boolean throwExceptionOnFailure) {
try {
setupExceptionOnFailure(throwExceptionOnFailure);
return tryFindValueWhenExpressionIsNotNull(expr);
} catch (OgnlException e) {
return handleOgnlException(expr, throwExceptionOnFailure, e);
} catch (Exception e) {
return handleOtherException(expr, throwExceptionOnFailure, e);
} finally {
ReflectionContextState.clear(context);
}
}

private void setupExceptionOnFailure(boolean throwExceptionOnFailure) {
if (throwExceptionOnFailure) {
context.put(THROW_EXCEPTION_ON_FAILURE, true);
}
}

private Object tryFindValueWhenExpressionIsNotNull(String expr) throws OgnlException {
if (expr == null) {
return null;
}
return tryFindValue(expr);
}

private Object handleOtherException(String expr, boolean throwExceptionOnFailure, Exception e) {
logLookupFailure(expr, e);

if (throwExceptionOnFailure)
throw new XWorkException(e);

return findInContext(expr);
}

private Object tryFindValue(String expr) throws OgnlException {
Object value;
expr = lookupForOverrides(expr);
if (defaultType != null) {
value = findValue(expr, defaultType);
} else {
value = getValueUsingOgnl(expr);
if (value == null) {
value = findInContext(expr);
}
}
return value;
}

private String lookupForOverrides(String expr) {
if ((overrides != null) && overrides.containsKey(expr)) {
expr = (String) overrides.get(expr);
}
return expr;
}

private Object getValueUsingOgnl(String expr) throws OgnlException {
try {
return ognlUtil.getValue(expr, context, root);
} finally {
context.remove(THROW_EXCEPTION_ON_FAILURE);
}
}

public Object findValue(String expr) {
return findValue(expr, false);
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#findValue(java.lang.String, java.lang.Class)
*/
public Object findValue(String expr, Class asType, boolean throwExceptionOnFailure) {
try {
setupExceptionOnFailure(throwExceptionOnFailure);
return tryFindValueWhenExpressionIsNotNull(expr, asType);
} catch (OgnlException e) {
return handleOgnlException(expr, throwExceptionOnFailure, e);
} catch (Exception e) {
return handleOtherException(expr, throwExceptionOnFailure, e);
} finally {
ReflectionContextState.clear(context);
}
}

private Object tryFindValueWhenExpressionIsNotNull(String expr, Class asType) throws OgnlException {
if (expr == null) {
return null;
}
return tryFindValue(expr, asType);
}

private Object handleOgnlException(String expr, boolean throwExceptionOnFailure, OgnlException e) {
Object ret = findInContext(expr);
if (ret == null) {
if (shouldLogNoSuchPropertyWarning(e)) {
LOG.warn("Could not find property [" + ((NoSuchPropertyException) e).getName() + "]");
}
if (throwExceptionOnFailure) {
throw new XWorkException(e);
}
}
return ret;
}

private boolean shouldLogNoSuchPropertyWarning(OgnlException e) {
return e instanceof NoSuchPropertyException && devMode && logMissingProperties;
}

private Object tryFindValue(String expr, Class asType) throws OgnlException {
Object value = null;
try {
expr = lookupForOverrides(expr);
value = getValue(expr, asType);
if (value == null) {
value = findInContext(expr);
}
} finally {
context.remove(THROW_EXCEPTION_ON_FAILURE);
}
return value;
}

private Object getValue(String expr, Class asType) throws OgnlException {
return ognlUtil.getValue(expr, context, root, asType);
}

private Object findInContext(String name) {
return getContext().get(name);
}

public Object findValue(String expr, Class asType) {
return findValue(expr, asType, false);
}

/**
* Log a failed lookup, being more verbose when devMode=true.
*
* @param expr The failed expression
* @param e    The thrown exception.
*/
private void logLookupFailure(String expr, Exception e) {
String msg = LoggerUtils.format("Caught an exception while evaluating expression '#0' against value stack", expr);
if (devMode && LOG.isWarnEnabled()) {
LOG.warn(msg, e);
LOG.warn("NOTE: Previous warning message was issued due to devMode set to true.");
} else if (LOG.isDebugEnabled()) {
LOG.debug(msg, e);
}
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#peek()
*/
public Object peek() {
return root.peek();
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#pop()
*/
public Object pop() {
return root.pop();
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#push(java.lang.Object)
*/
public void push(Object o) {
root.push(o);
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#set(java.lang.String, java.lang.Object)
*/
public void set(String key, Object o) {
//set basically is backed by a Map pushed on the stack with a key being put on the map and the Object being the value
Map setMap = retrieveSetMap();
setMap.put(key, o);
}

private Map retrieveSetMap() {
Map setMap;
Object topObj = peek();
if (shouldUseOldMap(topObj)) {
setMap = (Map) topObj;
} else {
setMap = new HashMap();
setMap.put(MAP_IDENTIFIER_KEY, "");
push(setMap);
}
return setMap;
}

/**
* check if this is a Map put on the stack  for setting if so just use the old map (reduces waste)
*/
private boolean shouldUseOldMap(Object topObj) {
return topObj instanceof Map && ((Map) topObj).get(MAP_IDENTIFIER_KEY) != null;
}

/**
* @see com.opensymphony.xwork2.util.ValueStack#size()
*/
public int size() {
return root.size();
}

private Object readResolve() {
// TODO: this should be done better
ActionContext ac = ActionContext.getContext();
Container cont = ac.getContainer();
XWorkConverter xworkConverter = cont.getInstance(XWorkConverter.class);
CompoundRootAccessor accessor = (CompoundRootAccessor) cont.getInstance(PropertyAccessor.class, CompoundRoot.class.getName());
TextProvider prov = cont.getInstance(TextProvider.class, "system");
boolean allow = "true".equals(cont.getInstance(String.class, "allowStaticMethodAccess"));
OgnlValueStack aStack = new OgnlValueStack(xworkConverter, accessor, prov, allow);
aStack.setOgnlUtil(cont.getInstance(OgnlUtil.class));
aStack.setRoot(xworkConverter, accessor, this.root, allow);

return aStack;
}

public void clearContextValues() {
//this is an OGNL ValueStack so the context will be an OgnlContext
//it would be better to make context of type OgnlContext
((OgnlContext) context).getValues().clear();
}

public void setAcceptProperties(Set<Pattern> acceptedProperties) {
securityMemberAccess.setAcceptProperties(acceptedProperties);
}

public void setPropertiesJudge(PropertiesJudge judge) {
securityMemberAccess.setPropertiesJudge(judge);
}

public void setExcludeProperties(Set<Pattern> excludeProperties) {
securityMemberAccess.setExcludeProperties(excludeProperties);
}

}