1、

String sql = null;
if(null == renderType || renderType.equals(ConstantRender.sql_renderType_beetl)){
   if(log.isDebugEnabled()) log.debug("beetl解析sql");
   sql = BeetlKit.render(sqlTemplete, param);
   
} else if(renderType.equals(ConstantRender.sql_renderType_freeMarker)){
   if(log.isDebugEnabled()) log.debug("FreeMarker解析sql");
   sql = ToolFreeMarker.render(sqlTemplete, param);
   
} else if(renderType.equals(ConstantRender.sql_renderType_velocity)){
   if(log.isDebugEnabled()) log.debug("Velocity解析sql");
   sql = ToolVelocity.render(sqlTemplete, param);
} 

2、beetl:

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.beetl.core;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import org.beetl.core.resource.StringTemplateResourceLoader;
import org.beetl.ext.fn.GetValueFunction;

public class BeetlKit {
    public static GroupTemplate gt = null;

    public BeetlKit() {
    }

    public static String render(String template, Map<String, Object> paras) {
        Template t = gt.getTemplate(template);
        t.binding(paras);
        return t.render();
    }

    public static void renderTo(String template, Writer writer, Map<String, Object> paras) {
        Template t = gt.getTemplate(template);
        t.binding(paras);
        t.renderTo(writer);
    }

    public static void execute(String script, Map<String, Object> paras) {
        execute(script, paras, (String[])null);
    }

    public static Map execute(String script, Map<String, Object> paras, String[] locals) {
        String start = gt.getConf().getStatementStart();
        String end = gt.getConf().getStatementEnd();
        StringBuilder sb = new StringBuilder(script.length() + start.length() + end.length());
        sb.append(start).append(script);
        if (locals != null) {
            sb.append("beetlKit(");
            String[] var6 = locals;
            int var7 = locals.length;

            for(int var8 = 0; var8 < var7; ++var8) {
                String varName = var6[var8];
                sb.append("'").append(varName).append("',").append(varName).append("!,");
            }

            sb.setLength(sb.length() - 1);
            sb.append(");");
        }

        sb.append(end);
        Template t = gt.getTemplate(sb.toString());
        t.binding(paras);
        HashMap map = new HashMap();
        t.binding("beetlKitMap", map);
        t.render();
        return map;
    }

    public static Map executeAndReturnRootScopeVars(String script) {
        String start = gt.getConf().getStatementStart();
        String end = gt.getConf().getStatementEnd();
        StringBuilder sb = new StringBuilder(script.length() + start.length() + end.length());
        sb.append(start).append(script);
        sb.append(end);
        Template t = gt.getTemplate(sb.toString());
        t.render();
        Map<String, Integer> idnexMap = t.program.metaData.getTemplateRootScopeIndexMap();
        Object[] values = t.ctx.vars;
        Map<String, Object> result = new HashMap();
        Iterator var8 = idnexMap.entrySet().iterator();

        while(var8.hasNext()) {
            Entry<String, Integer> entry = (Entry)var8.next();
            String name = (String)entry.getKey();
            int index = (Integer)entry.getValue();
            Object value = values[index];
            result.put(name, value);
        }

        return result;
    }

    public static String testTemplate(String template, String initValue) {
        Map map = executeAndReturnRootScopeVars(initValue);
        String result = render(template, map);
        return result;
    }

    public static void main(String[] args) {
        String template = "${a}";
        String initValue = "var a=1,c=2+1";
        String result = testTemplate(template, initValue);
        System.out.println(result);
    }

    static {
        StringTemplateResourceLoader resourceLoader = new StringTemplateResourceLoader();

        Configuration cfg;
        try {
            cfg = Configuration.defaultConfiguration();
        } catch (IOException var3) {
            throw new RuntimeException(var3);
        }

        gt = new GroupTemplate(resourceLoader, cfg);
        gt.registerFunction("beetlKit", new GetValueFunction());
        gt.setErrorHandler(new ConsoleErrorHandler() {
            protected void println(Writer w, String msg) {
                try {
                    w.write(msg);
                    w.write(10);
                } catch (IOException var4) {
                    var4.printStackTrace();
                }

            }

            protected void print(Writer w, String msg) {
                try {
                    w.write(msg);
                } catch (IOException var4) {
                    var4.printStackTrace();
                }

            }

            protected void printThrowable(Writer w, Throwable t) {
                t.printStackTrace(new PrintWriter(w));
            }

            protected String getResourceName(String resourceId) {
                return resourceId.length() > 10 ? resourceId.substring(0, 10).concat("...") : resourceId;
            }
        });
    }
}

3、FreeMarker： 

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.Map;

import com.jfinal.log.Log;

import freemarker.cache.TemplateLoader;
import freemarker.template.Configuration;
import freemarker.template.DefaultObjectWrapper;
import freemarker.template.Template;
import freemarker.template.TemplateException;

/**
 * FreeMarker工具類 
 */
public abstract class ToolFreeMarker {

   private static final Log log = Log.getLog(ToolFreeMarker.class);
   
   /**
    * 渲染模板
    * @param templateContent
    * @param paramMap
    * @return
    */
   public static String render(String templateContent, Map<String, Object> paramMap) {
      StringWriter writer = new StringWriter();
      try {
         Configuration cfg = new Configuration(Configuration.VERSION_2_3_22);
         cfg.setTemplateLoader(new StringTemplateLoader(templateContent));
         cfg.setDefaultEncoding("UTF-8");

         Template template = cfg.getTemplate("");

         template.process(paramMap, writer);
      } catch (IOException e) {
         e.printStackTrace();
         if(log.isErrorEnabled()) log.error(e.getMessage());
      } catch (TemplateException e) {
         e.printStackTrace();
         if(log.isErrorEnabled()) log.error(e.getMessage());
      }
      return writer.toString();
   }
   
   /**
    * 生成HTML
    * @param tlDirectory tl模板目錄
    * @param tlName   ftl模板
    * @param paramMap 引數map
    * @param htmlPath 生成HTML存放路徑
    */
   public static void makeHtml(String tlDirectory, String tlName, Map<String, Object> paramMap, String htmlPath) {
      FileOutputStream fileOutputStream = null;
      OutputStreamWriter outputStreamWriter = null;
      try {
         Configuration configuration = new Configuration(Configuration.VERSION_2_3_22);
         File file = new File(tlDirectory);// .ftl模板目錄
         configuration.setDirectoryForTemplateLoading(file);
         configuration.setObjectWrapper(new DefaultObjectWrapper(Configuration.VERSION_2_3_22));
         Template template = configuration.getTemplate(tlName, ToolString.encoding);

         File file2 = new File(htmlPath);// 生成html目錄
         fileOutputStream = new FileOutputStream(file2);
         outputStreamWriter = new OutputStreamWriter(fileOutputStream, ToolString.encoding);
         BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter);
         template.process(paramMap, bufferedWriter);
         bufferedWriter.flush();
         outputStreamWriter.close();
         fileOutputStream.close();
      } catch (IOException e) {
         e.printStackTrace();
      } catch (TemplateException e) {
         e.printStackTrace();
      } finally {
         if (null != fileOutputStream) {
            try {
               fileOutputStream.close();
            } catch (IOException e) {
               e.printStackTrace();
            }
         }
         if (null != outputStreamWriter) {
            try {
               outputStreamWriter.close();
            } catch (IOException e) {
               e.printStackTrace();
            }
         }
      }
   }

}

class StringTemplateLoader implements TemplateLoader {

   private String template;

   public StringTemplateLoader(String template) {
      this.template = template;
      if (template == null) {
         this.template = "";
      }
   }

   public void closeTemplateSource(Object templateSource) throws IOException {
      ((StringReader) templateSource).close();
   }

   public Object findTemplateSource(String name) throws IOException {
      return new StringReader(template);
   }

   public long getLastModified(Object templateSource) {
      return 0;
   }

   public Reader getReader(Object templateSource, String encoding) throws IOException {
      return (Reader) templateSource;
   }

}

4、Velocity： 

import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Map;
import java.util.Set;

import org.apache.velocity.Template;
import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.app.VelocityEngine;
import org.apache.velocity.exception.ParseErrorException;
import org.apache.velocity.exception.ResourceNotFoundException;

import com.jfinal.log.Log;

/**
 * Velocity工具類 
 */
public abstract class ToolVelocity {

   @SuppressWarnings("unused")
   private static final Log log = Log.getLog(ToolVelocity.class);

   /**
    * 渲染模板
    * @param templateContent
    * @param paramMap
    * @return
    */
   public static String render(String templateContent, Map<String, Object> paramMap) {
      // 初始化並取得Velocity引擎
      VelocityEngine ve = new VelocityEngine();
      ve.init();

      // 取得velocity的上下文context
      VelocityContext context = new VelocityContext();
      
      Set<String> keys = paramMap.keySet();
      for (String key : keys) {
         context.put(key, paramMap.get(key));// 把資料填入上下文
      }

      // 輸出流
      StringWriter writer = new StringWriter();

      // 轉換輸出
      ve.evaluate(context, writer, "", templateContent); // 關鍵方法

      return writer.toString();
   }
   
   /**
    * 生成靜態html
    * @param tlPath 模板路徑
    * @param paramMap 引數
    * @param htmlPath html檔案儲存路徑
    */
   public static void makeHtml(String tlPath, Map<String, Object> paramMap, String htmlPath) {
      PrintWriter pw = null;
      try {
            //初始化vm模板
            Template template = Velocity.getTemplate(tlPath, "UTF-8");
           
            //初始化上下文
            VelocityContext context = new VelocityContext();
            
            //新增資料到上下文中
            Set<String> keys = paramMap.keySet();
            for (String key : keys) {
               context.put(key, paramMap.get(key));
         }
            
            //生成html頁面
            pw = new PrintWriter(htmlPath);
            template.merge(context, pw);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (ResourceNotFoundException e) {
            e.printStackTrace();
        } catch (ParseErrorException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
           if(pw != null ){
                //關閉流
              pw.close();
           }
        }
   }
   
}