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Use String#isEmpty()

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Closes gh-1335
(cherry picked from commit 7d062df)
This commit is contained in:
stonio
2017-02-21 16:23:40 +01:00
committed by Juergen Hoeller
parent 34a0857628
commit 1db42081e5
15 changed files with 93 additions and 110 deletions
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102
spring-expression/src/main/java/org/springframework/expression/common/TemplateAwareExpressionParser.java
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@@ -1,5 +1,5 @@
/*
* Copyright 2002-2013 the original author or authors.
* Copyright 2002-2017 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
@@ -40,31 +40,28 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
* Default ParserContext instance for non-template expressions.
*/
private static final ParserContext NON_TEMPLATE_PARSER_CONTEXT = new ParserContext() {
@Override
public String getExpressionPrefix() {
return null;
}
@Override
public String getExpressionSuffix() {
return null;
}
@Override
public boolean isTemplate() {
return false;
}
};
@Override
public Expression parseExpression(String expressionString) throws ParseException {
return parseExpression(expressionString, NON_TEMPLATE_PARSER_CONTEXT);
}
@Override
public Expression parseExpression(String expressionString, ParserContext context)
throws ParseException {
public Expression parseExpression(String expressionString, ParserContext context) throws ParseException {
if (context == null) {
context = NON_TEMPLATE_PARSER_CONTEXT;
}
@@ -77,11 +74,12 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
}
}
private Expression parseTemplate(String expressionString, ParserContext context)
throws ParseException {
if (expressionString.length() == 0) {
private Expression parseTemplate(String expressionString, ParserContext context) throws ParseException {
if (expressionString.isEmpty()) {
return new LiteralExpression("");
}
Expression[] expressions = parseExpressions(expressionString, context);
if (expressions.length == 1) {
return expressions[0];
@@ -109,8 +107,7 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
* @return the parsed expressions
* @throws ParseException when the expressions cannot be parsed
*/
private Expression[] parseExpressions(String expressionString, ParserContext context)
throws ParseException {
private Expression[] parseExpressions(String expressionString, ParserContext context) throws ParseException {
List<Expression> expressions = new LinkedList<Expression>();
String prefix = context.getExpressionPrefix();
String suffix = context.getExpressionSuffix();
@@ -120,35 +117,29 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
if (prefixIndex >= startIdx) {
// an inner expression was found - this is a composite
if (prefixIndex > startIdx) {
expressions.add(createLiteralExpression(context,
expressionString.substring(startIdx, prefixIndex)));
expressions.add(new LiteralExpression(expressionString.substring(startIdx, prefixIndex)));
}
int afterPrefixIndex = prefixIndex + prefix.length();
int suffixIndex = skipToCorrectEndSuffix(prefix, suffix,
expressionString, afterPrefixIndex);
int suffixIndex = skipToCorrectEndSuffix(suffix, expressionString, afterPrefixIndex);
if (suffixIndex == -1) {
throw new ParseException(expressionString, prefixIndex,
"No ending suffix '" + suffix
+ "' for expression starting at character "
+ prefixIndex + ": "
+ expressionString.substring(prefixIndex));
"No ending suffix '" + suffix + "' for expression starting at character " +
prefixIndex + ": " + expressionString.substring(prefixIndex));
}
if (suffixIndex == afterPrefixIndex) {
throw new ParseException(expressionString, prefixIndex,
"No expression defined within delimiter '" + prefix + suffix
+ "' at character " + prefixIndex);
"No expression defined within delimiter '" + prefix + suffix +
"' at character " + prefixIndex);
}
String expr = expressionString.substring(prefixIndex + prefix.length(),
suffixIndex);
String expr = expressionString.substring(prefixIndex + prefix.length(), suffixIndex);
expr = expr.trim();
if (expr.length() == 0) {
if (expr.isEmpty()) {
throw new ParseException(expressionString, prefixIndex,
"No expression defined within delimiter '" + prefix + suffix
+ "' at character " + prefixIndex);
"No expression defined within delimiter '" + prefix + suffix +
"' at character " + prefixIndex);
}
expressions.add(doParseExpression(expr, context));
@@ -156,18 +147,13 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
}
else {
// no more ${expressions} found in string, add rest as static text
expressions.add(createLiteralExpression(context,
expressionString.substring(startIdx)));
expressions.add(new LiteralExpression(expressionString.substring(startIdx)));
startIdx = expressionString.length();
}
}
return expressions.toArray(new Expression[expressions.size()]);
}
private Expression createLiteralExpression(ParserContext context, String text) {
return new LiteralExpression(text);
}
/**
* Return true if the specified suffix can be found at the supplied position in the
* supplied expression string.
@@ -192,15 +178,15 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
/**
* Copes with nesting, for example '${...${...}}' where the correct end for the first
* ${ is the final }.
* @param prefix the prefix
* @param suffix the suffix
* @param expressionString the expression string
* @param afterPrefixIndex the most recently found prefix location for which the
* matching end suffix is being sought
* matching end suffix is being sought
* @return the position of the correct matching nextSuffix or -1 if none can be found
*/
private int skipToCorrectEndSuffix(String prefix, String suffix,
String expressionString, int afterPrefixIndex) throws ParseException {
private int skipToCorrectEndSuffix(String suffix, String expressionString, int afterPrefixIndex)
throws ParseException {
// Chew on the expression text - relying on the rules:
// brackets must be in pairs: () [] {}
// string literals are "..." or '...' and these may contain unmatched brackets
@@ -226,16 +212,15 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
case ']':
case ')':
if (stack.isEmpty()) {
throw new ParseException(expressionString, pos, "Found closing '"
+ ch + "' at position " + pos + " without an opening '"
+ Bracket.theOpenBracketFor(ch) + "'");
throw new ParseException(expressionString, pos, "Found closing '" + ch +
"' at position " + pos + " without an opening '" +
Bracket.theOpenBracketFor(ch) + "'");
}
Bracket p = stack.pop();
if (!p.compatibleWithCloseBracket(ch)) {
throw new ParseException(expressionString, pos, "Found closing '"
+ ch + "' at position " + pos
+ " but most recent opening is '" + p.bracket
+ "' at position " + p.pos);
throw new ParseException(expressionString, pos, "Found closing '" + ch +
"' at position " + pos + " but most recent opening is '" + p.bracket +
"' at position " + p.pos);
}
break;
case '\'':
@@ -244,8 +229,7 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
int endLiteral = expressionString.indexOf(ch, pos + 1);
if (endLiteral == -1) {
throw new ParseException(expressionString, pos,
"Found non terminating string literal starting at position "
+ pos);
"Found non terminating string literal starting at position " + pos);
}
pos = endLiteral;
break;
@@ -254,9 +238,8 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
}
if (!stack.isEmpty()) {
Bracket p = stack.pop();
throw new ParseException(expressionString, p.pos, "Missing closing '"
+ Bracket.theCloseBracketFor(p.bracket) + "' for '" + p.bracket
+ "' at position " + p.pos);
throw new ParseException(expressionString, p.pos, "Missing closing '" +
Bracket.theCloseBracketFor(p.bracket) + "' for '" + p.bracket + "' at position " + p.pos);
}
if (!isSuffixHere(expressionString, pos, suffix)) {
return -1;
@@ -265,6 +248,17 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
}
/**
* Actually parse the expression string and return an Expression object.
* @param expressionString the raw expression string to parse
* @param context a context for influencing this expression parsing routine (optional)
* @return an evaluator for the parsed expression
* @throws ParseException an exception occurred during parsing
*/
protected abstract Expression doParseExpression(String expressionString, ParserContext context)
throws ParseException;
/**
* This captures a type of bracket and the position in which it occurs in the
* expression. The positional information is used if an error has to be reported
@@ -313,14 +307,4 @@ public abstract class TemplateAwareExpressionParser implements ExpressionParser
}
}
/**
* Actually parse the expression string and return an Expression object.
* @param expressionString the raw expression string to parse
* @param context a context for influencing this expression parsing routine (optional)
* @return an evaluator for the parsed expression
* @throws ParseException an exception occurred during parsing
*/
protected abstract Expression doParseExpression(String expressionString,
ParserContext context) throws ParseException;
}