freemarker中实现自定义标签

import


 java.io.IOException;
 
import


 java.io.Writer;
 
import


 java.util.Iterator;
 
import


 java.util.Map;

 
import


 freemarker
.core.Environment;
import


 freemarker
.template.SimpleNumber;
import


 freemarker
.template.TemplateBooleanModel;
import


 freemarker
.template.TemplateDirectiveBody;
import


 freemarker
.template.TemplateDirectiveModel
;
import


 freemarker
.template.TemplateException;
import


 freemarker
.template.TemplateModel;
import


 freemarker
.template.TemplateModelException;
import


 freemarker
.template.TemplateNumberModel;

/**
 * FreeMarker
 自定义标签实现重复输出内容体。
 *
 *
 * 参数:
 * count: 重复的次数，必须的且非负整数。
 * hr: 设置是否输出HTML标签 "hr" 元素. Boolean. 可选的默认为fals.
 *
 *
 * 循环变量: 只有一个，可选的. 从1开始。
 *
 *
 */
public


 
class


 RepeatDirective 
implements


 TemplateDirectiveModel
 {

    
private


 
static


 
final


 String PARAM_NAME_COUNT = 
"count"

;
    
private


 
static


 
final


 String PARAM_NAME_HR = 
"hr"

;

    
public


 
void


 execute(Environment env, Map params, TemplateModel[] loopVars,
            TemplateDirectiveBody body) 
throws


 TemplateException, IOException {

        
// ---------------------------------------------------------------------
        
// 处理参数

        
int


 countParam = 
0

;
        
boolean


 countParamSet = 
false


;
        
boolean


 hrParam = 
false


;

        Iterator paramIter = params.entrySet().iterator();
        
while


 (paramIter.hasNext()) {
            Map.Entry ent = (Map.Entry) paramIter.next();

            String paramName = (String) ent.getKey();
            TemplateModel paramValue = (TemplateModel) ent.getValue();

            
if


 (paramName.equals(PARAM_NAME_COUNT)) {
                
if


 (!(paramValue 
instanceof


 TemplateNumberModel)) {
                    
throw


 
new


 TemplateModelException(
"The \""

 + PARAM_NAME_HR
                            + 
"\" parameter "

 + 
"must be a number."

);
                }
                countParam = ((TemplateNumberModel) paramValue).getAsNumber()
                        .intValue();
                countParamSet = 
true


;
                
if


 (countParam < 
0

) {
                    
throw


 
new


 TemplateModelException(
"The \""

 + PARAM_NAME_HR
                            + 
"\" parameter "

 + 
"can't be negative."

);
                }
            } 
else


 
if


 (paramName.equals(PARAM_NAME_HR)) {
                
if


 (!(paramValue 
instanceof


 TemplateBooleanModel)) {
                    
throw


 
new


 TemplateModelException(
"The \""

 + PARAM_NAME_HR
                            + 
"\" parameter "

 + 
"must be a boolean."

);
                }
                hrParam = ((TemplateBooleanModel) paramValue).getAsBoolean();
            } 
else


 {
                
throw


 
new


 TemplateModelException(
"Unsupported parameter: "
                        + paramName);
            }
        }
        
if


 (!countParamSet) {
            
throw


 
new


 TemplateModelException(
"The required \""
                    + PARAM_NAME_COUNT + 
"\" paramter"

 + 
"is missing."

);
        }

        
if


 (loopVars.length > 
1

) {
            
throw


 
new


 TemplateModelException(
                    
"At most one loop variable is allowed."

);
        }

        
// Yeah, it was long and boring...

        
// ---------------------------------------------------------------------
        
// 真正开始处理输出内容

        Writer out = env.getOut();
        
if


 (body != 
null


) {
            
for


 (
int


 i = 
0

; i < countParam; i++) {
                
// 输出  <hr> 如果 参数hr 设置为true
                
if


 (hrParam && i != 
0

) {
                    out.write(
"<hr>"

);
                }

                
// 设置循环变量
                
if


 (loopVars.length > 
0

) {
                    loopVars[
0

] = 
new


 SimpleNumber(i + 
1

);
                }

                
// 执行标签内容(same as <#nested> in FTL).
                body.render(env.getOut());
            }
        }
    }

}

import java.io.IOException;
import java.io.Writer;
import java.util.Iterator;
import java.util.Map;
 
import freemarker
.core.Environment;
import freemarker
.template.SimpleNumber;
import freemarker
.template.TemplateBooleanModel;
import freemarker
.template.TemplateDirectiveBody;
import freemarker
.template.TemplateDirectiveModel
;
import freemarker
.template.TemplateException;
import freemarker
.template.TemplateModel;
import freemarker
.template.TemplateModelException;
import freemarker
.template.TemplateNumberModel;
/**
 * FreeMarker
 自定义标签实现重复输出内容体。
 * 
 * 
 * 参数:
 * count: 重复的次数，必须的且非负整数。
 * hr: 设置是否输出HTML标签 "hr" 元素. Boolean. 可选的默认为fals.
 * 
 * 
 * 循环变量: 只有一个，可选的. 从1开始。
 * 
 * 
 */
public class RepeatDirective implements TemplateDirectiveModel
 {
private static final String PARAM_NAME_COUNT = "count";
private static final String PARAM_NAME_HR = "hr";
public void execute(Environment env, Map params, TemplateModel[] loopVars,
TemplateDirectiveBody body) throws TemplateException, IOException {
// ---------------------------------------------------------------------
// 处理参数
int countParam = 0;
boolean countParamSet = false;
boolean hrParam = false;
Iterator paramIter = params.entrySet().iterator();
while (paramIter.hasNext()) {
Map.Entry ent = (Map.Entry) paramIter.next();
String paramName = (String) ent.getKey();
TemplateModel paramValue = (TemplateModel) ent.getValue();
if (paramName.equals(PARAM_NAME_COUNT)) {
if (!(paramValue instanceof TemplateNumberModel)) {
throw new TemplateModelException("The \"" + PARAM_NAME_HR
+ "\" parameter " + "must be a number.");
}
countParam = ((TemplateNumberModel) paramValue).getAsNumber()
.intValue();
countParamSet = true;
if (countParam < 0) {
throw new TemplateModelException("The \"" + PARAM_NAME_HR
+ "\" parameter " + "can't be negative.");
}
} else if (paramName.equals(PARAM_NAME_HR)) {
if (!(paramValue instanceof TemplateBooleanModel)) {
throw new TemplateModelException("The \"" + PARAM_NAME_HR
+ "\" parameter " + "must be a boolean.");
}
hrParam = ((TemplateBooleanModel) paramValue).getAsBoolean();
} else {
throw new TemplateModelException("Unsupported parameter: "
+ paramName);
}
}
if (!countParamSet) {
throw new TemplateModelException("The required \""
+ PARAM_NAME_COUNT + "\" paramter" + "is missing.");
}
if (loopVars.length > 1) {
throw new TemplateModelException(
"At most one loop variable is allowed.");
}
// Yeah, it was long and boring...
// ---------------------------------------------------------------------
// 真正开始处理输出内容
Writer out = env.getOut();
if (body != null) {
for (int i = 0; i < countParam; i++) {
// 输出  <hr> 如果 参数hr 设置为true
if (hrParam && i != 0) {
out.write("<hr>");
}
// 设置循环变量
if (loopVars.length > 0) {
loopVars[0] = new SimpleNumber(i + 1);
}
// 执行标签内容(same as <#nested> in FTL). 
body.render(env.getOut());
}
}
}
}

 

import


 java.io.File;
import


 java.io.IOException;
import


 java.io.Writer;
import


 java.util.Map;

import


 freemarker
.template.Configuration;
import


 freemarker
.template.DefaultObjectWrapper;
import


 freemarker
.template.Template;
import


 freemarker
.template.TemplateException;

/**
 *
 * 模板工具类
 */
public


 
class


 FreeMarkertUtil {
    
/**
     * @param templatePath 模板文件存放目录
     * @param templateName 模板文件名称
     * @param root 数据模型根对象
     * @param templateEncoding 模板文件的编码方式
     * @param out 输出流
     */
    
public


 
static


 
void


 processTemplate(String templatePath, String templateName, String templateEncoding, Map<?,?> root, Writer out){
        
try


 {
            Configuration config=
new


 Configuration();
            File file=
new


 File(templatePath);
            
//设置要解析的模板所在的目录，并加载模板文件
            config.setDirectoryForTemplateLoading(file);
            
//设置包装器，并将对象包装为数据模型
            config.setObjectWrapper(
new


 DefaultObjectWrapper());

            
//获取模板,并设置编码方式，这个编码必须要与页面中的编码格式一致
            Template template=config.getTemplate(templateName,templateEncoding);
            
//合并数据模型与模板

            template.process(root, out);
            out.flush();
            out.close();
        } 
catch


 (IOException e) {
            e.printStackTrace();
        }
catch


 (TemplateException e) {
            e.printStackTrace();
        }

    }
}

import java.io.File;
import java.io.IOException;
import java.io.Writer;
import java.util.Map;
 
import freemarker
.template.Configuration;
import freemarker
.template.DefaultObjectWrapper;
import freemarker
.template.Template;
import freemarker
.template.TemplateException;
/**
 * 
 * 模板工具类
 */
public class FreeMarkertUtil {
/**
 * @param templatePath 模板文件存放目录 
 * @param templateName 模板文件名称 
 * @param root 数据模型根对象
 * @param templateEncoding 模板文件的编码方式
 * @param out 输出流
 */
public static void processTemplate(String templatePath, String templateName, String templateEncoding, Map<?,?> root, Writer out){
try {
Configuration config=new Configuration();
File file=new File(templatePath);
//设置要解析的模板所在的目录，并加载模板文件
config.setDirectoryForTemplateLoading(file);
//设置包装器，并将对象包装为数据模型
config.setObjectWrapper(new DefaultObjectWrapper());
//获取模板,并设置编码方式，这个编码必须要与页面中的编码格式一致
Template template=config.getTemplate(templateName,templateEncoding);
//合并数据模型与模板
    template.process(root, out);
    out.flush();
    out.close();
} catch (IOException e) {
e.printStackTrace();
}catch (TemplateException e) {
e.printStackTrace();
}
} 
}

 

 

import


 java.io.OutputStreamWriter;
import


 java.util.HashMap;
import


 java.util.Map;

/**
 *
 * 客户端测试模板输入类
 */
public


 
class


 RepeatTest {
    
public


 
static


 
void


 main(String[] args) {
        Map<String,Object> root=
new


 HashMap<String, Object>();

        root.put(
"repeat"

, 
new


 RepeatDirective());

        FreeMarkertUtil.processTemplate(
"src/templates"

,
"repeat.ftl"

, 
"UTF-8"

, root, 
new


 OutputStreamWriter(System.out));

    }
}

import java.io.OutputStreamWriter;
import java.util.HashMap;
import java.util.Map;
 
/**
 * 
 * 客户端测试模板输入类
 */
public class RepeatTest {
public static void main(String[] args) {
Map<String,Object> root=new HashMap<String, Object>();
root.put("repeat", new RepeatDirective());
FreeMarkertUtil.processTemplate("src/templates","repeat.ftl", "UTF-8", root, new OutputStreamWriter(System.out));
}
}

 

 模板文件repeat.ftl如下：

 

<#assign x = 
1

>

一个参数：
<
@repeat

 count=
4

>
  Test ${x}
  <#assign x = x + 
1

>
</
@repeat

>

二个参数：
<
@repeat

 count=
3

 hr=
true


>
  Test
</
@repeat

>

循环变量：
<
@repeat

 count=
3

; cnt>
  ${cnt}. Test
</
@repeat

>

<#assign x = 1>
 
一个参数：
<@repeat count=4>
  Test ${x}
  <#assign x = x + 1>
</@repeat>
二个参数：
<@repeat count=3 hr=true>
  Test
</@repeat>
循环变量：
<@repeat count=3; cnt>
  ${cnt}. Test
</@repeat>  

 

 输出结果：

Java代码

一个参数：
  Test 
1
  Test 
2
  Test 
3
  Test 
4

二个参数：
  Test
<hr>  Test
<hr>  Test

循环变量：
  
1

. Test
  
2

. Test
  
3

. Test