Scala正則和抽取器：解析方法參數(shù)
在《正則表達(dá)式基礎(chǔ)知識》中概括了正則表達(dá)式的基礎(chǔ)知識， 本文講解如何使用正則表達(dá)式解析方法參數(shù)，從而可以根據(jù) DAO 自動生成 Service.
在做 Java 項(xiàng)目時，常常要根據(jù) DAO 生成 Service , 而 Service 有時是簡單的調(diào)用 DAO 方法。比如根據(jù) public CreativeDO findByCreativeId(Long creativeId) 生成如下代碼：
public CreativeDO findByCreativeId(Long creativeId) {
return creativeDAO.findByCreativeId(creativeId);
}實(shí)際上就是將分號替換成帶左右大括號的部分， 而 return 語句里可變的部分是方法名稱 (findByCreativeId)、方法列表 (creativeId) ， 因此，需要從方法簽名中提取出方法名稱和參數(shù)列表。正則表達(dá)式尤其適合做這件事。
編寫正則表達(dá)式的技巧：
1. 從簡單的表達(dá)式寫起， 反復(fù)試驗(yàn)，逐步逼近；
2. 分而治之：將要匹配的字符串分解成有意義的小組，分別寫出匹配小組的子正則表達(dá)式，然后組合成完整的正則表達(dá)式；
3. 為了兼容處理輸入含前導(dǎo)后綴空格的情況，通常在正則表達(dá)式前后添加 \s*Regex\s* 。
從最簡單的開始
編寫正則表達(dá)式，從最簡單的開始。先處理只有一個參數(shù)的方法簽名，可以拆解為方法名稱及方法參數(shù)列表兩個部分：
val methodNameRegexStr = "\\s*(?:\\w+\\s+)?\\w+<?\\w+>?\\s+(\\w+)"
val singleParamRegexStr = "[^,]*\\w+<?\\w+>?\\s+(\\w+)\\s*"
val simpleMethodSignRexStr = methodNameRegexStr + "\\(" + singleParamRegexStr + "\\)\\s*;\\s*"這里小小地使用到了"分而治之"的技巧。其中：
1. 帶訪問修飾符或不帶訪問修飾符：CreativeDO findByCreativeId(Long creativeId) 或 public CreativeDO findByCreativeId(Long creativeId) ; 這里使用了 (?:\\w+\\s+)? 來匹配帶 public 或不帶 public 的情況， ? 表示可有可無；(?:regex) 表示匹配 regex 的字符串但是并不捕獲該分組，這是由于只要使用了小括號的正則都會被捕獲，可以在后續(xù)引用匹配結(jié)果，但是這里 public 并不是我們感興趣的目標(biāo)，忽略掉；
2. 參數(shù)可能是集合類型： \\w+? ， 比如 List
3. 方法名稱使用了 (\\w+) 來捕獲；
4. 方法參數(shù)中使用 \\w+?
來匹配參數(shù)類型， 比如 Long 或 List
5. 合并起來就是 simpleMethodSignRexStr 用來匹配單參數(shù)的方法簽名。
使用： 在字符串上調(diào)用方法 r 即可獲取對應(yīng)的正則表達(dá)式用來匹配； 使用 regex(values) = text 可以從 text 中抽取匹配 regex 中的分組的值 values 。
val methodSign = " int insert(@Param(\"kdtId\") BuyerAddressDO buyerAddressDO); "
val simpleMethodSignRex = simpleMethodSignRexStr.r
val simpleMethodSignRex(methodName, arg) = methodSign
println(methodName + " " + arg)處理雙參數(shù)
有了匹配單參數(shù)方法簽名的正則表達(dá)式， 又有匹配單參數(shù)的正則表達(dá)式， 編寫處理雙參數(shù)的方法簽名就簡單多了：
val twoParamMethodSignRegStr = methodNameRegexStr + "\\(" + singleParamRegexStr + "," + singleParamRegexStr + "\\);\\s*"這里感受到了正則表達(dá)式復(fù)用的滋味了吧！^_^
使用：
val twoParamMethodSign = "OrderExpressDO getById(@Param(\"id\") int id, @Param(\"kdtId\") int kdtId); "
val twoParamMethodSignRex = twoParamMethodSignRegStr.r
val twoParamMethodSignRex(methodName2, arg1, arg2) = twoParamMethodSign
println(List(methodName2, arg1 + ", " + arg2))處理任意多個參數(shù)
通常擴(kuò)展下雙參數(shù)情況就可以了?！?/p>
//val generalParamMethodSignRegStr = methodNameRegexStr + "\\((" + singleParamRegexStr + "(?:," + singleParamRegexStr + ")*)\\);\\s*"不過，事實(shí)卻沒有那么美好。即使這樣能夠匹配整個方法簽名，卻只能捕獲第一個參數(shù)和最后一個參數(shù)，中間的參數(shù)會被忽略。怎么辦了？查看 Scala 正則表達(dá)式的部分尋找答案，發(fā)現(xiàn)抽取器似乎能夠解決整個問題。
抽取器
抽取器并不是什么特別的事物，只是 Scala 增加的一個語法糖，用于從對象值中抽取出感興趣的值或值集合；就好比 Java 里實(shí)現(xiàn)了迭代器方法的對象都可以使用 foreach 遍歷一樣。實(shí)際上， val twoParamMethodSignRex(methodName2, arg1, arg2) = twoParamMethodSign 已經(jīng)使用到了抽取器的語法，這里正則表達(dá)式實(shí)現(xiàn)了抽取器的功能。只要對象實(shí)現(xiàn)了 unapply 或 unapplySeq 就可以使用抽取器語法。對于解析方法簽名這個例子，可以先將參數(shù)列表使用正則表達(dá)式抽取出來，然后用逗號分隔，最后使用單參數(shù)正則表達(dá)式(又一次復(fù)用！) 抽取，實(shí)現(xiàn)如下：
val generalParamMethodSignRegStr = methodNameRegexStr + "\\((.*)\\);\\s*"
object Method {
def unapplySeq(methodSign:String): Option[(String, Seq[String])] = {
try {
val generalParamMethodSignReg = generalParamMethodSignRegStr.r
val generalParamMethodSignReg(methodName, args) = methodSign
val params = args.split(',').toList
val argNames = params.map(extractArgName(_))
println("parsed: " + Some(methodName, argNames))
Some(methodName, argNames)
} catch {
case _ => Some("", List())
}
}
def extractArgName(singleParam: String): String = {
val singleParamRegex = singleParamRegexStr.r
val singleParamRegex(argName) = singleParam
return argName
}
}然后可以這樣使用：
generalParamMethodSign match {
case Method(methodName, firstArg, restArgs @ _*) =>
println("Case Match Way: " + methodName + "(" + firstArg + ", " + restArgs.mkString(", ") + ")")
case _ => println("Not matched")
}
val Method(methodName5, firstArg, restArgs @ _*) = generalParamMethodSign
println("Extractor Way: " + methodName5 + "(" + firstArg + ", " + restArgs.mkString(", ") + ")")其中：firstArg 是抽取列表的第一個元素， restArgs 是抽取列表的剩余元素。如果寫成 val Method(methodName, args) = generalParamMethodSign 是不行的，估計是因?yàn)榱斜硎峭ㄟ^鏈表的形式實(shí)現(xiàn)的：列表總是第一個元素鏈接到剩余元素的列表。
完整代碼：
package scalastudy.basic
import java.io.PrintWriter
import scalastudy.utils.DefaultFileUtil._
import scalastudy.utils.PathConstants
/**
* Created by shuqin on 16/4/22.
*/
object AutoGenerateJavaCodes extends App {
val methodNameRegexStr = "\\s*(?:\\w+\\s+)?\\w+<?\\w+>?\\s+(\\w+)"
val singleParamRegexStr = "[^,]*\\w+<?\\w+>?\\s+(\\w+)\\s*"
val simpleMethodSignRexStr = methodNameRegexStr + "\\(" + singleParamRegexStr + "\\)\\s*;\\s*"
val twoParamMethodSignRegStr = methodNameRegexStr + "\\(" + singleParamRegexStr + "," + singleParamRegexStr + "\\);\\s*"
//val generalParamMethodSignRegStr = methodNameRegexStr + "\\((" + singleParamRegexStr + "(?:," + singleParamRegexStr + ")*)\\);\\s*"
val generalParamMethodSignRegStr = methodNameRegexStr + "\\((.*)\\);\\s*"
val apiPackageName = "cc.lovesqcc"
launch()
object Method {
def unapplySeq(methodSign:String): Option[(String, Seq[String])] = {
try {
val generalParamMethodSignReg = generalParamMethodSignRegStr.r
val generalParamMethodSignReg(methodName, args) = methodSign
val params = args.split(',').toList
val argNames = params.map(extractArgName(_))
println("parsed: " + Some(methodName, argNames))
Some(methodName, argNames)
} catch {
case _ => Some("", List())
}
}
def extractArgName(singleParam: String): String = {
val singleParamRegex = singleParamRegexStr.r
val singleParamRegex(argName) = singleParam
return argName
}
}
def generateJavaFile(filepath: String): List[Any] = {
val basePath = "/tmp/"
val biz = List("order", "payment")
var writePath = basePath
var bizType = ""
biz.foreach { e =>
if (filepath.contains(e)) {
writePath = writePath + "/" + e + "/"
bizType = e
}
}
val daoFileName = extraFilename(filepath)
val daoClassName = daoFileName.substring(0, daoFileName.indexOf('.'))
val writeFilename = writePath + daoFileName.replaceAll("DAO", "ServiceImpl")
val serviceClassName = daoClassName.replace("DAO", "ServiceImpl")
val daoRefName = firstLower(daoClassName)
val lines = readFileLines(filepath)
var fileContents = ""
var daoFlag = false
lines.foreach { line =>
if (daoFlag) {
fileContents += "\n\t@Resource\n"
fileContents += "\tprivate " + daoClassName + " " + daoRefName + ";\n\n"
daoFlag = false
}
else if (line.contains("interface")) {
fileContents += "@Service\npublic class " + serviceClassName + " implements " + daoClassName.replace("DAO", "Service") + " { \n"
daoFlag = true
}
else if (line.contains(";")) {
if (!line.contains("import") && !line.contains("package")) {
val parsed = parseMethod(line)
val replaceStr = " {\n\t\treturn " + daoRefName + "." + parsed(0) + "(" + parsed(1) + ");\n\t}\n"
var assertQualifier = ""
if (!line.contains("public")) {
assertQualifier = "public "
}
fileContents += "\t" + assertQualifier + " " + line.trim.replace(";", replaceStr)
}
else if (line.contains("package")) {
fileContents += line.replace("dao", "service") + "\n\n"
var bizTypeStr = "."
if (bizType.length > 0) {
bizTypeStr = "." + bizType + "."
}
fileContents += "import " + apiPackageName + bizTypeStr + "service." + daoClassName.replace("DAO", "Service") + ";\n"
fileContents += "import javax.annotation.Resource;\n"
fileContents += "import org.springframework.stereotype.Service;\n"
}
else {
fileContents += line + "\n"
}
}
else {
fileContents += line + "\n"
}
}
mkdir(writePath)
val writeFile = new PrintWriter(writeFilename)
writeFile.println(fileContents)
writeFile.close
return List[Any]();
}
def daoRefName(daoClassName: String): String = {
return firstLower(daoClassName)
}
def firstLower(str: String): String = {
return str.charAt(0).toLower + str.substring(1)
}
def parseMethod(methodSign: String): List[String] = {
val simpleMethodSignRex = simpleMethodSignRexStr.r
try {
val Method(methodName, firstArg, restArgs @ _*) = methodSign
if (restArgs.size == 0) {
return List(methodName, firstArg)
}
else {
return List(methodName, firstArg + ", " + restArgs.mkString(", "))
}
} catch {
case _ => return List("", "")
}
}
def debug(): Unit = {
// simple catch regex groups
val methodSign = " int insert(@Param(\"kdtId\") BuyerAddressDO buyerAddressDO); "
val simpleMethodSignRex = simpleMethodSignRexStr.r
val simpleMethodSignRex(methodName, arg) = methodSign
println(methodName + " " + arg)
val twoParamMethodSign = "OrderExpressDO getById(@Param(\"id\") int id, @Param(\"kdtId\") int kdtId); "
val twoParamMethodSignRex = twoParamMethodSignRegStr.r
val twoParamMethodSignRex(methodName2, arg1, arg2) = twoParamMethodSign
println(List(methodName2, arg1 + ", " + arg2))
val text = "Good query(@Param(\"goodId\") goodId, int kdtId)"
val regex = "\\s*(?:\\w+\\s+)?\\w+<?\\w+>?\\s+(\\w+)\\((.*)\\)".r
val regex(methodName3, wholearg1) = text
println(methodName3 + " " + wholearg1);
val generalParamMethodSign = " OrderDO queryOrder(@Param(\"orderNos\") List<String> orderNos, @Param(\"page\") Integer page, @Param(\"pageSize\") Integer pageSize, boolean flag); "
val regex2 = generalParamMethodSignRegStr.r
val regex2(methodName4, wholearg2) = generalParamMethodSign
println(methodName4 + " : " + wholearg2);
generalParamMethodSign match {
case Method(methodName, firstArg, restArgs @ _*) =>
println("Case Match Way: " + methodName + "(" + firstArg + ", " + restArgs.mkString(", ") + ")")
case _ => println("Not matched")
}
val Method(methodName5, firstArg, restArgs @ _*) = generalParamMethodSign
println("Extractor Way: " + methodName5 + "(" + firstArg + ", " + restArgs.mkString(", ") + ")")
}
def testParseMethod(): Unit = {
val testMethods = Map(
" List<OrderDO> queryOrder(int kdtId); " -> List("queryOrder", "kdtId"),
" List<OrderDO> queryOrder( int kdtId ); " -> List("queryOrder", "kdtId"),
" OrderDO queryOrder(@Param(\"kdtId\") int kdtId); " -> List("queryOrder", "kdtId"),
" List<OrderDO> queryOrder(List<String> orderNos); " -> List("queryOrder", "orderNos"),
" List<OrderDO> queryOrder(@Param(\"orderNos\") List<String> orderNos); " -> List("queryOrder", "orderNos"),
" OrderDO queryOrder(String orderNo, Integer kdtId); " -> List("queryOrder", "orderNo, kdtId"),
" OrderDO queryOrder(String orderNo, @Param(\"kdtId\") Integer kdtId); " -> List("queryOrder", "orderNo, kdtId"),
" OrderDO queryOrder(@Param(\"orderNo\") String orderNo, Integer kdtId); " -> List("queryOrder", "orderNo, kdtId"),
" OrderDO queryOrder(@Param(\"orderNo\") String orderNo, @Param(\"kdtId\") Integer kdtId); " -> List("queryOrder", "orderNo, kdtId"),
" OrderDO queryOrder(List<String> orderNos, Integer kdtId); \n" -> List("queryOrder", "orderNos, kdtId"),
" OrderDO queryOrder(@Param(\"orderNos\") List<String> orderNos, Integer kdtId); " -> List("queryOrder", "orderNos, kdtId"),
" OrderDO queryOrder(List<String> orderNos, @Param(\"kdtId\") Integer kdtId); " -> List("queryOrder", "orderNos, kdtId"),
" OrderDO queryOrder(@Param(\"orderNos\") List<String> orderNos, @Param(\"kdtId\") Integer kdtId); " -> List("queryOrder", "orderNos, kdtId"),
" OrderDO queryOrder(@Param(\"orderNos\") List<String> orderNos, @Param(\"page\") Integer page, @Param(\"pageSize\") Integer pageSize); " -> List("queryOrder", "orderNos, page, pageSize"))
testMethods.foreach { testMethod =>
println("test method: " + testMethod._1)
val parsed = parseMethod(testMethod._1)
println(parsed)
assert(parseMethod(testMethod._1) == testMethod._2)
}
println("test ParseMethod passed.")
}
def launch(): Unit = {
debug
testParseMethod
val dirpath = "/tmp/";
handleFiles(fetchAllFiles)((file: String) => file.endsWith("DAO.java"))(List(generateJavaFile(_)))((liststr: List[Any]) => "")(dirpath);
}
}出處：cnblogs.com/lovesqcc/p/5450238.html
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