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Java > Open Source Codes > org > apache > commons > el > ConditionalExpression


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55
56 package org.apache.commons.el;
57
58 import java.util.List JavaDoc;
59 import java.util.Map JavaDoc;
60 import javax.servlet.jsp.el.ELException JavaDoc;
61 import javax.servlet.jsp.el.VariableResolver JavaDoc;
62 import javax.servlet.jsp.el.FunctionMapper JavaDoc;
63
64 /**
65  *
66  * <p>Represents a conditional expression. I've decided not to produce an
67  * abstract base "TernaryOperatorExpression" class since (a) future ternary
68  * operators are unlikely and (b) it's not clear that there would be a
69  * meaningful way to abstract them. (For instance, would they all be right-
70  * associative? Would they all have two fixed operator symbols?)
71  *
72  * @author Shawn Bayern
73  **/
74
75 public class ConditionalExpression
76   extends Expression
77 {
78   //-------------------------------------
79 // Properties
80 //-------------------------------------
81 // property condition
82
83   Expression mCondition;
84   public Expression getCondition ()
85   { return mCondition; }
86   public void setCondition (Expression pCondition)
87   { mCondition = pCondition; }
88
89   //-------------------------------------
90 // property trueBranch
91
92   Expression mTrueBranch;
93   public Expression getTrueBranch ()
94   { return mTrueBranch; }
95   public void setTrueBranch (Expression pTrueBranch)
96   { mTrueBranch = pTrueBranch; }
97
98   //-------------------------------------
99 // property falseBranch
100
101   Expression mFalseBranch;
102   public Expression getFalseBranch ()
103   { return mFalseBranch; }
104   public void setFalseBranch (Expression pFalseBranch)
105   { mFalseBranch = pFalseBranch; }
106
107   //-------------------------------------
108 /**
109    *
110    * Constructor
111    **/
112   public ConditionalExpression (Expression pCondition,
113                 Expression pTrueBranch,
114                 Expression pFalseBranch)
115   {
116     mCondition = pCondition;
117     mTrueBranch = pTrueBranch;
118     mFalseBranch = pFalseBranch;
119   }
120
121   //-------------------------------------
122 // Expression methods
123 //-------------------------------------
124 /**
125    *
126    * Returns the expression in the expression language syntax
127    **/
128   public String JavaDoc getExpressionString ()
129   {
130     return
131       "( " + mCondition.getExpressionString() + " ? " +
132       mTrueBranch.getExpressionString() + " : " +
133       mFalseBranch.getExpressionString() + " )";
134   }
135
136   //-------------------------------------
137 /**
138    *
139    * Evaluates the conditional expression and returns the literal result
140    **/
141   public Object JavaDoc evaluate (VariableResolver JavaDoc vr,
142               FunctionMapper JavaDoc f,
143               Logger l)
144     throws ELException JavaDoc
145   {
146     // first, evaluate the condition (and coerce the result to a boolean value)
147 boolean condition =
148       Coercions.coerceToBoolean(
149         mCondition.evaluate(vr, f, l), l).booleanValue();
150
151     // then, use this boolean to branch appropriately
152 if (condition)
153       return mTrueBranch.evaluate(vr, f, l);
154     else
155       return mFalseBranch.evaluate(vr, f, l);
156   }
157
158   //-------------------------------------
159 }
160
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