[正则表达式]-----正向预搜索与反向预搜索 - 正则表达式

原创作者: site120 阅读:4537次评论:0条更新时间:2011-05-26

xml 代码

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!--
Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
<class name="cn.site120.TestRegex" table="XXX_123456_ver" dynamic-update="true" dynamic-insert="true">
<id name="id" type="java.lang.Long">
<column name="id" />
<generator class="native" />
</id>
<property name="name" type="java.lang.String">
<column name="name" length="50" />
</property>
<property name="versionNumber" type="java.lang.Integer">
<column name="versionNumber" not-null="true" />
</property>
</class>
</hibernate-mapping>

现在想用程序动态修改table="XXX_123456_ver"这里面的123456替换为其它代码,比如说022,010,等.

可以构造一个正则表达式来处理,由于这里面的123456也可能处于其它位置,比如: XXX_XXX_123456,所以可以这么来写

java 代码

String regex = "(?＜=_)([0-9]{3,4})(?=[_]?)";
File tmpdir = new File(System.getProperty("java.io.tmpdir"));
String classpath = TestNull.class.getClassLoader().getResource("").toString();
classpath = classpath.substring("file:/".length());
File configFile = new File(classpath + "config/XXX.hbm.xml");
BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(configFile)));
PrintWriter writer = new PrintWriter(tmpdir.getPath() + "/" + "XXX.hbm.xml");
StringBuffer content = new StringBuffer();
String temp = "";
while ((temp=reader.readLine()) != null)
{
content.append(temp);
content.append("\r\n");
}
StringBuffer content_new = new StringBuffer();
Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(content);
if (matcher.find())
{
matcher.appendReplacement(content_new , "123456");
}
matcher.appendTail(content_new);
//... 再将内容写到特定的目录下去. ...

这里面(?＜=_)([0-9]{3,4})(?=[_]?)中的(?＜=)为反向预搜索,表示在该缝隙的左边有一个"_"符号,且不参于匹配

(?=)表示正向预搜索,表示在该缝隙的右边可能有一个"_"符号,且不参于匹配

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