自己動(dòng)手實(shí)現(xiàn)mybatis動(dòng)態(tài)sql的方法

更新時(shí)間：2017年12月11日 09:19:31 作者：最后Q淚滴

下面小編就為大家分享一篇自己動(dòng)手實(shí)現(xiàn)mybatis動(dòng)態(tài)sql的方法，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。一起跟隨小編過來看看吧

發(fā)現(xiàn)要堅(jiān)持寫博客真的是一件很困難的事情，各種原因都會(huì)導(dǎo)致顧不上博客。本來打算寫自己動(dòng)手實(shí)現(xiàn)orm，看看時(shí)間，還是先實(shí)現(xiàn)一個(gè)動(dòng)態(tài)sql，下次有時(shí)間再補(bǔ)上orm完整的實(shí)現(xiàn)吧。

用過mybatis的人，估計(jì)對(duì)動(dòng)態(tài)sql都不陌生，如果沒有用過，就當(dāng)看看熱鬧吧。我第一次接觸mysql是在大四的時(shí)候，當(dāng)時(shí)就覺得動(dòng)態(tài)sql這東西很牛，很靈活，一直想搞明白怎么實(shí)現(xiàn)的，盡管當(dāng)時(shí)已經(jīng)能夠?qū)慽oc，mvc和簡單的orm框架(仿mybaits但是沒有動(dòng)態(tài)sql部分)，但是仍然找不到mybatis核心的動(dòng)態(tài)sql到底在哪實(shí)現(xiàn)的，怎么實(shí)現(xiàn)的，可能是那些代碼太繞根本沒法看懂，直到目前，我都沒有勇氣去看mybatis的動(dòng)態(tài)sql部分，大概是天生對(duì)算法有莫名其妙的敬畏吧。

幾年前因?yàn)橄胱鲆粋€(gè)配置平臺(tái)，想用解析型語言替代java的實(shí)現(xiàn)，可以讓配置人員在頁面上方便的編寫少量代碼實(shí)現(xiàn)復(fù)雜的業(yè)務(wù)邏輯（包括數(shù)據(jù)庫操作）。當(dāng)時(shí)java已經(jīng)有js解析引擎，但是大多數(shù)人都說效率太低，不知道我發(fā)什么瘋就想到自己實(shí)現(xiàn)一個(gè)解析語言。不過實(shí)現(xiàn)自己的語言也是我一直的夢想，解析語言相對(duì)編譯型語言入手簡單，于是我就果斷動(dòng)手了，寫完才知道，其實(shí)自己的實(shí)現(xiàn)估計(jì)還沒有當(dāng)時(shí)的js引擎效率高，那時(shí)的我真的是很年輕很簡單。今天談到的動(dòng)態(tài)sql實(shí)現(xiàn)其實(shí)就是受到那時(shí)候解析語言的啟發(fā)。

廢話不多說直接開始聊動(dòng)態(tài)sql，請看下面例子，先聲明這里的例子并不是一個(gè)正確的sql的寫法，只是想寫一個(gè)盡量復(fù)雜的嵌套結(jié)構(gòu)，如果把這種復(fù)雜的情況實(shí)現(xiàn)了，那么簡單一點(diǎn)的就更加不在話下了。

delete from pl_pagewidget
<if test="widgetcodes != null">
 where pagewidgetcode in
 <foreach collection="widgetcodes" item="item" index="index" open="(" separator="," close=")">
 <if test="index == 0">
 #{item}
 </if>
 <foreach collection="bs" item="b" index="index1" open="(" separator="," close=")">
  #
 </foreach>
 </foreach>
</if>
<if test="a != null">
 and a = #{a}
</if>

要實(shí)現(xiàn)解析出上面例子的sql，首先一個(gè)難點(diǎn)類似是test屬性里的條件怎么判斷真假，不過這個(gè)難點(diǎn)在struts2中學(xué)到的ognl表達(dá)式面前就比較小兒科了。不知道有么有朋友遇到過一個(gè)比較奇葩的現(xiàn)象，就是有時(shí)候明明在mybatis動(dòng)態(tài)sql中寫如下表達(dá)式，但是當(dāng)n=0的時(shí)候居然是滿足條件的也就是test里的值是false，0居然不能滿足這個(gè)表達(dá)式的條件，這里就是ognl庫的原因了。沒辦法它就是這么玩的，當(dāng)成特殊情況記住就可以了

test="n != null and n !=''"

ognl表達(dá)式使用很方便如下

import java.util.HashMap;
import java.util.Map;
import ognl.Ognl;
public class OgnlTest {
 //輸出結(jié)果:false
 public static void main(String[] args) throws Exception {
 String con1 = "n != null and n != ''";
 Map<String,Object> root = new HashMap<>();
 root.put("n", 0);
 System.out.println(Ognl.getValue(con1,root));
 }
}

要實(shí)現(xiàn)解析上面例子的sql，第二個(gè)難點(diǎn)就是雖然這個(gè)sql披上一層xml的皮就是一個(gè)標(biāo)準(zhǔn)的sql，如下

<sql>
 delete from pl_pagewidget
 <if test="widgetcodes != null">
 where pagewidgetcode in
 <foreach collection="widgetcodes" item="item" index="index" open="(" separator="," close=")">
 <if test="index == 0">
 #{item}
 </if>
 <foreach collection="bs" item="b" index="index1" open="(" separator="," close=")">
  #
 </foreach>
 </foreach>
 </if>
 <if test="a != null">
 and a = #{a}
 </if>
</sql>

但是要解析上面的xml和我們平時(shí)不一樣，這個(gè)xml是標(biāo)簽和文本混合的，正常我們開發(fā)中應(yīng)該很少會(huì)用到解析這種xml。不過我們常用的解析xml的工具dom4j其實(shí)可以很好的解析這種sql，只不過很少可能用到。Element類的content()方法就可以返回一個(gè)Node的集合，再通過遍歷這個(gè)集合，判斷每個(gè)Node的類型就可以了。解決了這兩個(gè)重點(diǎn)，只需要加上一點(diǎn)技巧就可以解析這種動(dòng)態(tài)sql了。

我用到的技巧是根據(jù)java語法格式得到的啟發(fā)。比如java中有局部變量和全局變量，不考慮引用傳遞這種情況，如果全局變量int i = 1；方法里面?zhèn)魅脒@個(gè)全局變量，然后在方法里面修改，在方法里面看到的是改變后的值，但是在方法外面看到的仍然是1。這個(gè)現(xiàn)象其實(shí)學(xué)過java應(yīng)該都知道。還有就是當(dāng)方法調(diào)用的時(shí)候，方法里面可以看到全局變量，也可以看到局部變量，方法調(diào)用結(jié)束后局部變量會(huì)被清空釋放(看垃圾搜集器高興)。介紹了這些直接上代碼了

import java.io.StringReader;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.commons.collections.MapUtils;
import org.apache.commons.lang.StringUtils;
import org.dom4j.Document;
import org.dom4j.Element;
import org.dom4j.Node;
import org.dom4j.Text;
import org.dom4j.io.SAXReader;
import com.rd.sql.Attrs;
import com.rd.sql.BaseNode;
import com.rd.sql.NodeFactory;
public class SqlParser {
 private Map<String,Object> currParams = new HashMap<String,Object>();
 
 /**
 delete from pl_pagewidget
 <if test="widgetcodes != null">
  where pagewidgetcode in
  <foreach collection="widgetcodes" item="item" index="index" open="(" separator="," close=")">
  <if test="index == 0">
  #{item}
  </if>
  <foreach collection="bs" item="b" index="index1" open="(" separator="," close=")">
  #
  </foreach>
  </foreach>
 </if>
 <if test="a != null">
  and a = #{a}
 </if>
 */
 public static void main(String[] args) throws Exception {
 Map<String, Object> map = new HashMap<String, Object>();
 map.put("widgetcodes", Arrays.asList("1", "2"));
 map.put("bs", Arrays.asList("3", "4"));
 map.put("a", 1);
 SqlParser parser = new SqlParser();
 System.out
  .println(parser.parser("delete from pl_pagewidget\n"
    + "\t<if test=\"widgetcodes != null\">\n"
    + "\t\twhere pagewidgetcode in\n"
    + "\t\t<foreach collection=\"widgetcodes\" item=\"item\" index=\"index\" open=\"(\" separator=\",\" close=\")\">\n"
    + "\t\t <if test=\"index == 0\">\n"
    + "\t\t #{item}\n"
    + "\t\t </if>\n"
    + "\t\t <foreach collection=\"bs\" item=\"b\" index=\"index1\" open=\"(\" separator=\",\" close=\")\">\n"
    + "\t\t\t#\n" + "\t\t </foreach>\n"
    + "\t\t</foreach>\n" + "\t</if>\n"
    + "\t<if test=\"a != null\">\n"
    + "\t\tand a = #{a}\n" + "\t</if>\n", map));
 System.out.println(parser.getParams());
 }
 public String parser(String xml, Map<String, Object> params)
  throws Exception {
 // xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"+xml;
 //給輸入的動(dòng)態(tài)sql套一層xml標(biāo)簽
 xml = "<sql>"+xml+"</sql>";
 SAXReader reader = new SAXReader(false);
 Document document = reader.read(new StringReader(xml));
 Element element = document.getRootElement();
 Map<String, Object> currParams = new HashMap<String, Object>();
 StringBuilder sb = new StringBuilder();
 //開始解析
 parserElement(element, currParams, params, sb);
 return sb.toString();
 }
 /**
 * 使用遞歸解析動(dòng)態(tài)sql
 * @param ele1 待解析的xml標(biāo)簽
 * @param currParams
 * @param globalParams
 * @param sb
 * @throws Exception
 */
 private void parserElement(Element ele1, Map<String, Object> currParams,
  Map<String, Object> globalParams, StringBuilder sb)
  throws Exception {
 // 解析一個(gè)節(jié)點(diǎn)，比如解析到了一個(gè)if節(jié)點(diǎn)，假如test判斷為true這里就返回true
 TempVal val = parserOneElement(currParams, globalParams, ele1, sb);
 //得到解析的這個(gè)節(jié)點(diǎn)的抽象節(jié)點(diǎn)對(duì)象
 BaseNode node = val.getNode();
 /**
  * 實(shí)際上這句之上的語句只是解析了xml的標(biāo)簽，并沒有解析標(biāo)簽里的內(nèi)容，這里
  * 表示要解析內(nèi)容之前，如果有前置操作做一點(diǎn)前置操作
  */
 node.pre(currParams, globalParams, ele1, sb);
 //判斷是否還需要解析節(jié)點(diǎn)里的內(nèi)容，例如if節(jié)點(diǎn)test結(jié)果為true
 boolean flag = val.isContinue();
 // 得到該節(jié)點(diǎn)下的所有子節(jié)點(diǎn)的集合，包含普通文本
 List<Node> nodes = ele1.content();
 if (flag && !nodes.isEmpty()) {
  /**
  * 這里表示要進(jìn)一步解析節(jié)點(diǎn)里的內(nèi)容了，可以把節(jié)點(diǎn)類比成一個(gè)方法的外殼
  * 里面的內(nèi)容類比成方法里的具體語句，開始解析節(jié)點(diǎn)的內(nèi)容之前
  * 先創(chuàng)建本節(jié)點(diǎn)下的局部參數(shù)的容器，最方便當(dāng)然是map
  */
  Map<String, Object> params = new HashMap<String, Object>();
  /**
  * 把外面?zhèn)鬟M(jìn)來的局部參數(shù)，直接放入容器，由于本例中參數(shù)都是常用數(shù)據(jù)類型
  * 不會(huì)存在引用類型所以，這里相當(dāng)于是一個(gè)copy，為了不影響外面?zhèn)魅氲膶?duì)象
  * 可以類比方法調(diào)用傳入?yún)?shù)的情況
  */
  params.putAll(currParams);
  //循環(huán)所有子節(jié)點(diǎn)
  for (int i = 0; i < nodes.size();) {
  Node n = nodes.get(i);
  //如果節(jié)點(diǎn)是普通文本
  if (n instanceof Text) {
   String text = ((Text) n).getStringValue();
   if (StringUtils.isNotEmpty(text.trim())) {
   //處理一下文本，如處理#{xx},直接替換${yy}為真實(shí)傳入的值
   sb.append(handText(text, params,globalParams));
   }
   i++;
  } else if (n instanceof Element) {
   Element e1 = (Element) n;
   // 遞歸解析xml子元素
   parserElement(e1, params, globalParams, sb);
   // 如果循環(huán)標(biāo)志不為true則解析下一個(gè)標(biāo)簽
   // 這里表示需要重復(fù)解析這個(gè)循環(huán)標(biāo)簽，則i不變,反之繼續(xù)處理下一個(gè)元素
   boolean while_flag = MapUtils.getBoolean(params,
    Attrs.WHILE_FLAG, false);
   if (!while_flag
    || !NodeFactory.isWhile(n.getName())
    || e1.attributeValue(Attrs.INDEX) == null
    || !e1.attributeValue(Attrs.INDEX).equals(
     params.get(Attrs.WHILE_INDEX))) {
   i++;
   }
  }
  }
  //節(jié)點(diǎn)處理之后做一些啥事
  node.after(currParams, globalParams, ele1, sb);
  // 回收當(dāng)前作用域參數(shù)
  params.clear();
  params = null;
 }
 }
 /**
 * 處理文本替換掉#{item}這種參數(shù)
 * @param str
 * @param params
 * @return
 * @throws Exception
 */
 private String handText(String str, Map<String, Object> params,Map<String, Object> globalParams)
  throws Exception {
 //獲取foreach這種標(biāo)簽中用于記錄循環(huán)的變量
 String indexStr = MapUtils.getString(params, Attrs.WHILE_INDEX);
 Integer index = null;
 if(StringUtils.isNotEmpty(indexStr)) {
  index = MapUtils.getInteger(params, indexStr);
 }
 //匹配#{a}這種參數(shù)
 String reg1 = "(#\\{)(\\w+)(\\})";
 //匹配${a}這種參數(shù)
 String reg2 = "(\\$\\{)(\\w+)(\\})";
 Pattern p1 = Pattern.compile(reg1);
 Matcher m1 = p1.matcher(str);
 Pattern p2 = Pattern.compile(reg2);
 Matcher m2 = p2.matcher(str);
 String whileList = MapUtils.getString(params, Attrs.WHILE_LIST);
 Map<String,Object> allParams = getAllParams(params, globalParams);
 while(m1.find()) {
  String tmpKey = m1.group(2);
  String key = whileList == null?tmpKey:(whileList+"_"+tmpKey);
  key = index == null?key:(key+index);
  String reKey = "#{"+key+"}";
  //如果在foreach類似的循環(huán)里，可能需要將參數(shù)#{xx}替換成#{xx_0},#{xx_1}
  str = str.replace(m1.group(0), reKey);
  currParams.put(key, allParams.get(tmpKey));
 }
 while(m2.find()) {
  String tmpKey = m2.group(2);
  Object value = allParams.get(tmpKey);
  if(value != null) {
  str = str.replace(m2.group(0), getValue(value));
  }
 }
 return str;
 }
 private String getValue(Object value) {
 String result = "";
 if(value instanceof Date) {
  SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
  result = sdf.format((Date)value);
 } else {
  result = String.valueOf(value);
 }
 return result;
 }
 private Map<String, Object> getAllParams(Map<String, Object> currParams,
  Map<String, Object> globalParams) {
 Map<String,Object> allParams = new HashMap<String,Object>();
 allParams.putAll(globalParams);
 allParams.putAll(currParams);
 return allParams;
 }
 
 // 解析一個(gè)xml元素
 private TempVal parserOneElement(Map<String, Object> currParams,
  Map<String, Object> globalParams, Element ele, StringBuilder sb)
  throws Exception {
 //獲取xml標(biāo)簽名
 String eleName = ele.getName();
 //解析一個(gè)節(jié)點(diǎn)后是否繼續(xù)，如遇到if這種節(jié)點(diǎn)，就需要判斷test里是否為空
 boolean isContinue = false;
 //聲明一個(gè)抽象節(jié)點(diǎn)
 BaseNode node = null;
 if (StringUtils.isNotEmpty(eleName)) {
  //使用節(jié)點(diǎn)工廠根據(jù)節(jié)點(diǎn)名得到一個(gè)節(jié)點(diǎn)對(duì)象比如是if節(jié)點(diǎn)還是foreach節(jié)點(diǎn)
  node = NodeFactory.create(eleName);
  //解析一下這個(gè)節(jié)點(diǎn)，返回是否還需要解析節(jié)點(diǎn)里的內(nèi)容
  isContinue = node.parse(currParams, globalParams, ele, sb);
 }
 return new TempVal(isContinue, ele, node);
 }
 public Map<String, Object> getParams() {
 return currParams;
 }
 /**
 * 封裝一個(gè)xml元素被解析后的結(jié)果
 * @author rongdi
 */
 final static class TempVal {
 private boolean isContinue;
 private Element ele;
 private BaseNode node;
 public TempVal(boolean isContinue, Element ele, BaseNode node) {
  this.isContinue = isContinue;
  this.ele = ele;
  this.node = node;
 }
 public boolean isContinue() {
  return isContinue;
 }
 public void setContinue(boolean isContinue) {
  this.isContinue = isContinue;
 }
 public Element getEle() {
  return ele;
 }
 public void setEle(Element ele) {
  this.ele = ele;
 }
 public BaseNode getNode() {
  return node;
 }
 public void setNode(BaseNode node) {
  this.node = node;
 }
 }
}

import org.dom4j.Element;
import java.util.HashMap;
import java.util.Map;
/**
 * 抽象節(jié)點(diǎn)
 * @author rongdi
 */
public abstract class BaseNode {
 public abstract boolean parse(Map<String, Object> currParams, Map<String, Object> globalParams, Element ele,StringBuilder sb) throws Exception;
 public void pre(Map<String, Object> currParams,Map<String, Object> globalParams,Element ele,StringBuilder sb) throws Exception {
 }
 public void after(Map<String, Object> currParams,Map<String, Object> globalParams,Element ele,StringBuilder sb) throws Exception {
 }
 protected Map<String, Object> getAllParams(Map<String, Object> currParams,
      Map<String, Object> globalParams) {
 Map<String,Object> allParams = new HashMap<String,Object>();
 allParams.putAll(globalParams);
 allParams.putAll(currParams);
 return allParams;
 }
}

import java.util.Map;
import ognl.Ognl;
import org.apache.commons.lang.StringUtils;
import org.dom4j.Element;
/**
 * if節(jié)點(diǎn)
 * @author rongdi
 */
public class IfNode extends BaseNode{
 @Override
 public boolean parse(Map<String, Object> currParams, Map<String, Object> globalParams, Element ele,StringBuilder sb) throws Exception {
 //得到if節(jié)點(diǎn)的test屬性
 String testStr = ele.attributeValue("test");
 boolean test = false;
 try {
  if(StringUtils.isNotEmpty(testStr)) {
  //合并全局變量和局部變量
  Map<String, Object> allParams = getAllParams(currParams,globalParams);
  //使用ognl判斷true或者false
  test = (Boolean) Ognl.getValue(testStr,allParams);
  }
 } catch (Exception e) {
  e.printStackTrace();
  throw new Exception("判斷操作參數(shù)"+testStr+"不合法");
 }
 if(ele.content() != null && ele.content().size()==0) {
  test = true;
 }
 return test;
 }
}

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import ognl.Ognl;
import org.apache.commons.collections.MapUtils;
import org.apache.commons.lang.StringUtils;
import org.dom4j.Element;
/**
 foreach節(jié)點(diǎn)屬性如下
 collection 需要遍歷的集合
 item 遍歷集合后每個(gè)元素存放的變量
 index 遍歷集合的索引數(shù)如0,1,2...
 separator 遍歷后以指定分隔符拼接
 open 遍歷后拼接開始的符號(hào)如 (
 close 遍歷后拼接結(jié)束的符號(hào)如 )
 */
public class ForeachNode extends BaseNode {
 @Override
 public boolean parse(Map<String, Object> currParams, Map<String, Object> globalParams, Element ele, StringBuilder sb) throws Exception {
 String conditionStr = null;
 String collectionStr = ele.attributeValue("collection");
 String itemStr = ele.attributeValue("item");
 String index = ele.attributeValue("index");
 String separatorStr = ele.attributeValue("separator");
 String openStr = ele.attributeValue("open");
 String closeStr = ele.attributeValue("close");
 if(StringUtils.isEmpty(index)) {
  index = "index";
 }
 if(StringUtils.isEmpty(separatorStr)) {
  separatorStr = ",";
 }
 if(StringUtils.isNotEmpty(openStr)) {
  currParams.put(Attrs.WHILE_OPEN,openStr);
 }
 if(StringUtils.isNotEmpty(closeStr)) {
  currParams.put(Attrs.WHILE_CLOSE,closeStr);
 }
 if(StringUtils.isNotEmpty(collectionStr)) {
  currParams.put(Attrs.WHILE_LIST,collectionStr);
 }
 currParams.put(Attrs.WHILE_SEPARATOR,separatorStr);
 if(index != null) {
  /**
  * 如果局部變量中存在當(dāng)前循環(huán)變量的值，就表示已經(jīng)不是第一次進(jìn)入循環(huán)標(biāo)簽了，移除掉開始標(biāo)記
  * 并將局部變量值加1
  */
  if(currParams.get(index) != null) {
  currParams.remove(Attrs.WHILE_START);
  currParams.put(index+"_", (Integer)currParams.get(index+"_") + 1);
  } else { //第一次進(jìn)入循環(huán)標(biāo)簽內(nèi)
  currParams.put(Attrs.WHILE_START,true);
  currParams.put(index+"_", 0);
  }
  currParams.put(index, (Integer)currParams.get(index+"_"));
 }
 boolean condition = true;
 Map<String, Object> allParams = getAllParams(currParams,globalParams);
 Object collection = null;
 if(StringUtils.isNotEmpty(collectionStr)) {
  //得到待循環(huán)的集合
  collection = Ognl.getValue(collectionStr,allParams);
  //如果集合屬性不為空，但是條件為null則默認(rèn)加上一個(gè)邊界條件
  if(StringUtils.isEmpty(conditionStr)) {
  //這里只是用集合演示一下，也可以再加上數(shù)組，只不過改成.length而已
  if(collection instanceof List) {
   conditionStr = index+"_<"+collectionStr+".size()";
  } else if(collection instanceof Map){
   Map map = (Map)collection;
   Set set = map.entrySet();
   List list = new ArrayList(set);
   allParams.put("_list_", list);
   conditionStr = index+"_<_list_"+".size()";
  }
  }
 }
 currParams.remove(Attrs.WHILE_END);
 if(StringUtils.isNotEmpty(conditionStr)) {
  //計(jì)算條件的值
  condition = (Boolean)Ognl.getValue(conditionStr,allParams);
  Map<String,Object> tempMap = new HashMap<>();
  tempMap.putAll(allParams);
  tempMap.put(index+"_",(Integer)currParams.get(index+"_") + 1);
  currParams.put(Attrs.WHILE_END,!(Boolean)Ognl.getValue(conditionStr,tempMap));
 }
 boolean flag = true;
 currParams.put(Attrs.WHILE_INDEX, index);
 currParams.put(Attrs.WHILE_FLAG, true);
 if(condition) {
  try {
  if(StringUtils.isNotEmpty(itemStr) && StringUtils.isNotEmpty(collectionStr)) {
   Object value = null;
   int idx = Integer.parseInt(currParams.get(index+"_").toString());
   if(collection instanceof List) {
   value = ((List)collection).get(idx);
   currParams.put(itemStr, value);
   } else if(collection instanceof Map){
   Map map = (Map)collection;
   Set<Map.Entry<String,Object>> set = map.entrySet();
   List<Map.Entry<String,Object>> list = new ArrayList(set);
   currParams.put(itemStr, list.get(idx).getValue());
   currParams.put(index, list.get(idx).getKey());
   }
  }
  } catch (Exception e) {
  throw new Exception("從集合或者映射取值"+currParams.get(index)+"錯(cuò)誤"+e.getMessage());
  }
 } else {
  flag = false;
  destroyVars(currParams, index, itemStr);
 }
 return flag;
 }
 /**
 * 如果是第一次進(jìn)入循環(huán)標(biāo)簽，則拼上open的內(nèi)容
 */
 @Override
 public void pre(Map<String, Object> currParams, Map<String, Object> globalParams, Element ele, StringBuilder sb) throws Exception {
 super.pre(currParams, globalParams, ele, sb);
 boolean start = MapUtils.getBoolean(currParams,Attrs.WHILE_START,false);
 if(start) {
  String open = MapUtils.getString(currParams,Attrs.WHILE_OPEN);
  sb.append(open);
 }
 }
 /**
 * 如果是最后進(jìn)入循環(huán)標(biāo)簽，則最后拼上close的內(nèi)容
 */
 @Override
 public void after(Map<String, Object> currParams, Map<String, Object> globalParams, Element ele, StringBuilder sb) throws Exception {
 super.after(currParams, globalParams, ele, sb);
 boolean end = MapUtils.getBoolean(currParams,Attrs.WHILE_END,false);
 String separator = MapUtils.getString(currParams,Attrs.WHILE_SEPARATOR);
 if(!end && StringUtils.isNotEmpty(separator)) {
  sb.append(separator);
 }
 if(end) {
  String close = MapUtils.getString(currParams,Attrs.WHILE_CLOSE);
  if(sb.toString().endsWith(separator)) {
  sb.deleteCharAt(sb.length() - 1);
  }
  sb.append(close);
 }
 }
 //釋放臨時(shí)變量
 private void destroyVars(Map<String, Object> currParams, String index,String varStr) {
 currParams.remove(Attrs.WHILE_INDEX);
 currParams.remove(Attrs.WHILE_FLAG);
 currParams.remove(Attrs.WHILE_SEPARATOR);
 currParams.remove(Attrs.WHILE_START);
 currParams.remove(Attrs.WHILE_END);
 currParams.remove(Attrs.WHILE_LIST);
　　　　}
}
 
import org.dom4j.Element;
import java.util.Map;
public class SqlNode extends BaseNode{
 @Override
 public boolean parse(Map<String, Object> currParams, Map<String, Object> globalParams, Element ele,StringBuilder sb) throws Exception {
 return true;
 }
}

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
 * 節(jié)點(diǎn)工廠
 */
public class NodeFactory {
 
 private static Map<String,BaseNode> nodeMap = new ConcurrentHashMap<String,BaseNode>();
 private final static List<String> whileList = Arrays.asList("foreach");
 static {
 nodeMap.put("if", new IfNode());
 nodeMap.put("sql", new SqlNode());
 nodeMap.put("foreach", new ForeachNode());
 }
 public static boolean isWhile(String elementName) {
 return whileList.contains(elementName);
 }
 public static void addNode(String nodeName,BaseNode node) {
 
 nodeMap.put(nodeName, node);
 
 }
 
 public static BaseNode create(String nodeName) {
 
 return nodeMap.get(nodeName);
 
 }
 
}

/**
 * 各種標(biāo)記
 * @author rongdi
 */
public class Attrs {
 
 public final static String TRANSACTIONAL = "transactional";
 public final static String WHILE_START = "while-start";
 public final static String WHILE_END = "while-end";
 public final static String WHILE_OPEN = "while-open";
 public final static String WHILE_CLOSE = "while-close";
 public final static String WHILE_SEPARATOR = "while-separator";
 public final static String WHILE_INDEX = "while-index";
 
 public final static String WHILE_FLAG = "while-flag";
 
 public final static String WHILE_LIST = "while-list";
 
 public final static String WHEN_FLAG = "when-flag";
 
 public static final String PROCESS_VAR = "process-var";
 
 public final static String RESULT_FLAG = "result-flag";
 
 public final static String RETURN_FLAG = "return-flag";
 
 public final static String CONSOLE_VAR= "console-var";
 
 public final static String DO = "do";
 
 public final static String INDEX = "index";
 
 public final static String CONDITION = "condition";
 
 public final static String NAME= "name";
 
 public final static String VALUE= "value";
 public static final String TYPE = "type";
 public static final String FORMAT = "format";
 
 public static final String IF = "if";
 
 public static final String ELSE = "else";
 
 public final static String FILE= "file";
 
 public static final String DATE = "date";
 
 public static final String NOW = "now";
 
 public static final String DECIMAL = "decimal";
 
 public static final String ID = "id";
 
 public static final String PARAMS = "params";
 public static final String TARGET = "target";
 public static final String SINGLE = "single";
 
 public static final String PAGING = "paging";
 public static final String DESC = "desc";
 public static final String BREAK = "break";
 
 public static final String CONTINUE = "continue";
 
 public static final String COLLECTION = "collection";
 public static final String VAR = "var";
 
 public static final String EXECUTOR = "executor-1";
 
 public static final String ROLLBACK_FLAG = "rollback-flag";
 
 public static final String SERVICE = "service";
 
 public static final String REF = "ref";
 public static final String BIZS = "bizs";
 public static final String TITLES = "titles";
 
 public static final String COLUMNS = "columns";
 
 public static final String CURRUSER = "currUser";
 
 public static final String CURRPERM = "currPerm";
 
 public static final String TASK_EXECUTOR = "taskExecutor";
 public static final String DELIMITER = "delimiter";
 public static final String OPERNAME = "operName";
 
}
 
 currParams.remove(varStr);
 currParams.remove(index);
 currParams.remove(index+"_");
 }
}

附上pom文件

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
 <modelVersion>4.0.0</modelVersion>
 <groupId>com.rd</groupId>
 <artifactId>parser</artifactId>
 <packaging>jar</packaging>
 <version>1.0-SNAPSHOT</version>
 <name>myparser</name>
 <url>http://maven.apache.org</url>
 <dependencies>
 <dependency>
  <groupId>dom4j</groupId>
  <artifactId>dom4j</artifactId>
  <version>1.6.1</version>
 </dependency>
 <dependency>
  <groupId>opensymphony</groupId>
  <artifactId>ognl</artifactId>
  <version>2.6.11</version>
 </dependency>
 <dependency>
  <groupId>commons-collections</groupId>
  <artifactId>commons-collections</artifactId>
  <version>3.2.1</version>
 </dependency>
 <dependency>
  <groupId>commons-lang</groupId>
  <artifactId>commons-lang</artifactId>
  <version>2.6</version>
 </dependency>
 <dependency>
  <groupId>junit</groupId>
  <artifactId>junit</artifactId>
  <version>3.8.1</version>
  <scope>test</scope>
 </dependency>
 </dependencies>
 <build>
 <resources>
  <resource>
  <directory>src/main/java</directory>
  <includes>
   <include>**/*.xml</include>
  </includes>
  </resource>
  <resource>
  <directory>src/main/resources</directory>
  <includes>
   <include>**/*</include>
  </includes>
  </resource>
 </resources>
 <testResources>
  <testResource>
  <directory>${project.basedir}/src/test/java</directory>
  </testResource>
  <testResource>
  <directory>${project.basedir}/src/test/resources</directory>
  </testResource>
 </testResources>
 <plugins>
  <plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>3.1</version>
  <configuration>
   <source>1.8</source>
   <target>1.8</target>
   <encoding>UTF-8</encoding>
  </configuration>
  </plugin>
 </plugins>
 </build>
</project>

以上這篇自己動(dòng)手實(shí)現(xiàn)mybatis動(dòng)態(tài)sql的方法就是小編分享給大家的全部內(nèi)容了，希望能給大家一個(gè)參考，也希望大家多多支持腳本之家。

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