Tomcat 8.x el 表示式的解析機制
阿新 • • 發佈：2019-02-09
解析EL表示式成物件樹
取得指定表示式的值
呼叫例子
out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${sessionScope.username}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
一些關鍵類
// javax.servlet.jsp.el.ImplicitObjectELResolver // org.apache.el.stream.StreamELResolverImpl // javax.el.StaticFieldELResolver // javax.el.MapELResolver !!! // javax.el.ResourceBundleELResolver // javax.el.ListELResolver // javax.el.ArrayELResolver // javax.el.BeanELResolver // javax.servlet.jsp.el.ScopedAttributeELResolver
主要的核心之一
javax.servlet.jsp.el.ImplicitObjectELResolver
public class ImplicitObjectELResolver extends ELResolver { private static final String[] SCOPE_NAMES = new String[] { "applicationScope", "cookie", "header", "headerValues", "initParam", "pageContext", "pageScope", "param", "paramValues", "requestScope", "sessionScope" }; private static final int APPLICATIONSCOPE = 0; private static final int COOKIE = 1; private static final int HEADER = 2; private static final int HEADERVALUES = 3; private static final int INITPARAM = 4; private static final int PAGECONTEXT = 5; private static final int PAGESCOPE = 6; private static final int PARAM = 7; private static final int PARAM_VALUES = 8; private static final int REQUEST_SCOPE = 9; private static final int SESSION_SCOPE = 10; public ImplicitObjectELResolver() { super(); } @Override public Object getValue(ELContext context, Object base, Object property) { Objects.requireNonNull(context); // context == org.apache.el.lang.EvaluationContext // 如： getValue(EvaluationContext, null, "applicationScope") // 如： getValue(org.apache.el.lang.EvaluationContext, javax.servlet.jsp.el.ImplicitObjectELResolver.ScopeMap, "username"); if (base == null && property != null) { int idx = Arrays.binarySearch(SCOPE_NAMES, property.toString()); // SCOPE_NAMES = new String[] { // "applicationScope", "cookie", "header", "headerValues", // "initParam", "pageContext", "pageScope", "param", "paramValues", // "requestScope", "sessionScope" } if (idx >= 0) { PageContext page = (PageContext) context .getContext(JspContext.class); // page === org.apache.jasper.runtime.PageContextImpl context.setPropertyResolved(base, property); switch (idx) { case APPLICATIONSCOPE: return ScopeManager.get(page).getApplicationScope(); // javax.servlet.jsp.el.ImplicitObjectELResolver.ScopeMap case COOKIE: return ScopeManager.get(page).getCookie(); case HEADER: return ScopeManager.get(page).getHeader(); case HEADERVALUES: return ScopeManager.get(page).getHeaderValues(); case INITPARAM: return ScopeManager.get(page).getInitParam(); case PAGECONTEXT: return ScopeManager.get(page).getPageContext(); case PAGESCOPE: return ScopeManager.get(page).getPageScope(); case PARAM: return ScopeManager.get(page).getParam(); case PARAM_VALUES: return ScopeManager.get(page).getParamValues(); case REQUEST_SCOPE: return ScopeManager.get(page).getRequestScope(); case SESSION_SCOPE: return ScopeManager.get(page).getSessionScope(); } } } return null; } @Override @SuppressWarnings({ "unchecked", "rawtypes" }) // TCK signature test fails with generics public Class getType(ELContext context, Object base, Object property) { Objects.requireNonNull(context); if (base == null && property != null) { int idx = Arrays.binarySearch(SCOPE_NAMES, property.toString()); if (idx >= 0) { context.setPropertyResolved(base, property); } } return null; } @Override public void setValue(ELContext context, Object base, Object property, Object value) { Objects.requireNonNull(context); if (base == null && property != null) { int idx = Arrays.binarySearch(SCOPE_NAMES, property.toString()); if (idx >= 0) { context.setPropertyResolved(base, property); throw new PropertyNotWritableException(); } } } @Override public boolean isReadOnly(ELContext context, Object base, Object property) { Objects.requireNonNull(context); if (base == null && property != null) { int idx = Arrays.binarySearch(SCOPE_NAMES, property.toString()); if (idx >= 0) { context.setPropertyResolved(base, property); return true; } } return false; } @Override public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) { List<FeatureDescriptor> feats = new ArrayList<>(SCOPE_NAMES.length); FeatureDescriptor feat; for (int i = 0; i < SCOPE_NAMES.length; i++) { feat = new FeatureDescriptor(); feat.setDisplayName(SCOPE_NAMES[i]); feat.setExpert(false); feat.setHidden(false); feat.setName(SCOPE_NAMES[i]); feat.setPreferred(true); feat.setValue(RESOLVABLE_AT_DESIGN_TIME, Boolean.TRUE); feat.setValue(TYPE, String.class); feats.add(feat); } return feats.iterator(); } @Override public Class<String> getCommonPropertyType(ELContext context, Object base) { if (base == null) { return String.class; } return null; } private static class ScopeManager { private static final String MNGR_KEY = ScopeManager.class.getName(); private final PageContext page; private Map<String,Object> applicationScope; private Map<String,Cookie> cookie; private Map<String,String> header; private Map<String,String[]> headerValues; private Map<String,String> initParam; private Map<String,Object> pageScope; private Map<String,String> param; private Map<String,String[]> paramValues; private Map<String,Object> requestScope; private Map<String,Object> sessionScope; public ScopeManager(PageContext page) { this.page = page; } public static ScopeManager get(PageContext page) { // page === org.apache.jasper.runtime.PageContextImpl ScopeManager mngr = (ScopeManager) page.getAttribute(MNGR_KEY); if (mngr == null) { mngr = new ScopeManager(page); page.setAttribute(MNGR_KEY, mngr); } return mngr; } public Map<String,Object> getApplicationScope() { if (this.applicationScope == null) { this.applicationScope = new ScopeMap<Object>() { // 建立物件 @Override protected void setAttribute(String name, Object value) { page.getServletContext().setAttribute(name, value); } @Override protected void removeAttribute(String name) { page.getServletContext().removeAttribute(name); } @Override protected Enumeration<String> getAttributeNames() { return page.getServletContext().getAttributeNames(); } @Override protected Object getAttribute(String name) { return page.getServletContext().getAttribute(name); } }; } return this.applicationScope; } public Map<String,Cookie> getCookie() { if (this.cookie == null) { this.cookie = new ScopeMap<Cookie>() { @Override protected Enumeration<String> getAttributeNames() { Cookie[] c = ((HttpServletRequest) page.getRequest()) .getCookies(); if (c != null) { Vector<String> v = new Vector<>(); for (int i = 0; i < c.length; i++) { v.add(c[i].getName()); } return v.elements(); } return null; } @Override protected Cookie getAttribute(String name) { Cookie[] c = ((HttpServletRequest) page.getRequest()) .getCookies(); if (c != null) { for (int i = 0; i < c.length; i++) { if (name.equals(c[i].getName())) { return c[i]; } } } return null; } }; } return this.cookie; } public Map<String,String> getHeader() { if (this.header == null) { this.header = new ScopeMap<String>() { @Override protected Enumeration<String> getAttributeNames() { return ((HttpServletRequest) page.getRequest()) .getHeaderNames(); } @Override protected String getAttribute(String name) { return ((HttpServletRequest) page.getRequest()) .getHeader(name); } }; } return this.header; } public Map<String,String[]> getHeaderValues() { if (this.headerValues == null) { this.headerValues = new ScopeMap<String[]>() { @Override protected Enumeration<String> getAttributeNames() { return ((HttpServletRequest) page.getRequest()) .getHeaderNames(); } @Override protected String[] getAttribute(String name) { Enumeration<String> e = ((HttpServletRequest) page.getRequest()) .getHeaders(name); if (e != null) { List<String> list = new ArrayList<>(); while (e.hasMoreElements()) { list.add(e.nextElement()); } return list.toArray(new String[list.size()]); } return null; } }; } return this.headerValues; } public Map<String,String> getInitParam() { if (this.initParam == null) { this.initParam = new ScopeMap<String>() { @Override protected Enumeration<String> getAttributeNames() { return page.getServletContext().getInitParameterNames(); } @Override protected String getAttribute(String name) { return page.getServletContext().getInitParameter(name); } }; } return this.initParam; } public PageContext getPageContext() { return this.page; } public Map<String,Object> getPageScope() { if (this.pageScope == null) { this.pageScope = new ScopeMap<Object>() { @Override protected void setAttribute(String name, Object value) { page.setAttribute(name, value); } @Override protected void removeAttribute(String name) { page.removeAttribute(name); } @Override protected Enumeration<String> getAttributeNames() { return page.getAttributeNamesInScope( PageContext.PAGE_SCOPE); } @Override protected Object getAttribute(String name) { return page.getAttribute(name); } }; } return this.pageScope; } public Map<String,String> getParam() { if (this.param == null) { this.param = new ScopeMap<String>() { @Override protected Enumeration<String> getAttributeNames() { return page.getRequest().getParameterNames(); } @Override protected String getAttribute(String name) { return page.getRequest().getParameter(name); } }; } return this.param; } public Map<String,String[]> getParamValues() { if (this.paramValues == null) { this.paramValues = new ScopeMap<String[]>() { @Override protected String[] getAttribute(String name) { return page.getRequest().getParameterValues(name); } @Override protected Enumeration<String> getAttributeNames() { return page.getRequest().getParameterNames(); } }; } return this.paramValues; } public Map<String,Object> getRequestScope() { if (this.requestScope == null) { this.requestScope = new ScopeMap<Object>() { @Override protected void setAttribute(String name, Object value) { page.getRequest().setAttribute(name, value); } @Override protected void removeAttribute(String name) { page.getRequest().removeAttribute(name); } @Override protected Enumeration<String> getAttributeNames() { return page.getRequest().getAttributeNames(); } @Override protected Object getAttribute(String name) { return page.getRequest().getAttribute(name); } }; } return this.requestScope; } public Map<String,Object> getSessionScope() { if (this.sessionScope == null) { this.sessionScope = new ScopeMap<Object>() { @Override protected void setAttribute(String name, Object value) { ((HttpServletRequest) page.getRequest()).getSession() .setAttribute(name, value); } @Override protected void removeAttribute(String name) { HttpSession session = page.getSession(); if (session != null) { session.removeAttribute(name); } } @Override protected Enumeration<String> getAttributeNames() { HttpSession session = page.getSession(); if (session != null) { return session.getAttributeNames(); } return null; } @Override protected Object getAttribute(String name) { HttpSession session = page.getSession(); if (session != null) { return session.getAttribute(name); } return null; } }; } return this.sessionScope; } } private abstract static class ScopeMap<V> extends AbstractMap<String,V> { protected abstract Enumeration<String> getAttributeNames(); protected abstract V getAttribute(String name); @SuppressWarnings("unused") protected void removeAttribute(String name) { throw new UnsupportedOperationException(); } @SuppressWarnings("unused") protected void setAttribute(String name, Object value) { throw new UnsupportedOperationException(); } @Override public final Set<Map.Entry<String,V>> entrySet() { Enumeration<String> e = getAttributeNames(); Set<Map.Entry<String, V>> set = new HashSet<>(); if (e != null) { while (e.hasMoreElements()) { set.add(new ScopeEntry(e.nextElement())); } } return set; } @Override public final int size() { int size = 0; Enumeration<String> e = getAttributeNames(); if (e != null) { while (e.hasMoreElements()) { e.nextElement(); size++; } } return size; } @Override public final boolean containsKey(Object key) { if (key == null) { return false; } Enumeration<String> e = getAttributeNames(); if (e != null) { while (e.hasMoreElements()) { if (key.equals(e.nextElement())) { return true; } } } return false; } private class ScopeEntry implements Map.Entry<String,V> { private final String key; public ScopeEntry(String key) { this.key = key; } @Override public String getKey() { return this.key; } @Override public V getValue() { return getAttribute(this.key); } @Override public V setValue(Object value) { if (value == null) { removeAttribute(this.key); } else { setAttribute(this.key, value); } return null; } @Override public boolean equals(Object obj) { return (obj != null && this.hashCode() == obj.hashCode()); } @Override public int hashCode() { return this.key.hashCode(); } } @Override public final V get(Object key) { // 取得屬性值 if (key != null) { return getAttribute((String) key); } return null; } @Override public final V put(String key, V value) { Objects.requireNonNull(key); if (value == null) { this.removeAttribute(key); } else { this.setAttribute(key, value); } return null; } @Override public final V remove(Object key) { Objects.requireNonNull(key); this.removeAttribute((String) key); return null; } } }
