public void write() throws IOException{ 
 HttpServletResponse response=ServletActionContext.getResponse(); 
 /* 
 * 在调用getWriter之前未设置编码(既调用setContentType或者setCharacterEncoding方法设置编码), 
 * HttpServletResponse则会返回一个用默认的编码(既ISO-8859-1)编码的PrintWriter实例。这样就会 
 * 造成中文乱码。而且设置编码时必须在调用getWriter之前设置,不然是无效的。 
 * */ 
 response.setContentType("text/html;charset=utf-8"); 
 //response.setCharacterEncoding("UTF-8"); 
 PrintWriter out = response.getWriter(); 
 //JSON在传递过程中是普通字符串形式传递的，这里简单拼接一个做测试 
 String jsonString="{\"user\":{\"id\":\"123\",\"name\":\"张三\",\"say\":\"Hello , i am a action to print a json!\",\"password\":\"JSON\"},\"success\":true}"; 
 out.println(jsonString); 
 out.flush(); 
 out.close(); 
}

<action name="write" class="json.JsonAction" method="write" /> 

{"user":{"id":"123","name":"张三","say":"Hello , i am a action to print a json!","password":"JSON"},"success":true} 

package json; 
 
import java.util.HashMap; 
import java.util.Map; 
 
import org.apache.struts2.json.annotations.JSON; 
import com.opensymphony.xwork2.ActionSupport; 
 
/** 
 * JSON测试 
 * 
 * @author Watson Xu 
 * @date 2012-8-4 下午06:21:01 
 */ 
public class JsonAction extends ActionSupport{ 
 private static final long serialVersionUID = 1L; 
 
 private Map<String,Object> dataMap; 
 private String key = "Just see see"; 
 
 public String json() { 
 // dataMap中的数据将会被Struts2转换成JSON字符串，所以这里要先清空其中的数据 
 dataMap = new HashMap<String, Object>(); 
 User user = new User(); 
 user.setName("张三"); 
 user.setPassword("123"); 
 dataMap.put("user", user); 
 // 放入一个是否操作成功的标识 
 dataMap.put("success", true); 
 // 返回结果 
 return SUCCESS; 
 } 
 
 public Map<String, Object> getDataMap() { 
 return dataMap; 
 } 
 
 //设置key属性不作为json的内容返回 
 @JSON(serialize=false) 
 public String getKey() { 
 return key; 
 } 
 
} 

<?xml version="1.0" encoding="UTF-8" ?> 
<!DOCTYPE struts PUBLIC 
 "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" 
 "http://struts.apache.org/dtds/struts-2.0.dtd"> 
<struts> 
 <package name="json" extends="struts-default,json-default" > 
 <action name="json" class="json.JsonAction" method="json"> 
 <result type="json"> 
 <!-- 这里指定将被Struts2序列化的属性，该属性在action中必须有对应的getter方法 --> 
 <param name="root">dataMap</param> 
 </result> 
 </action> 
 </package> 
</struts> 

{"success":true,"user":{"name":"张三","password":"123"}} 

<dependencies> 
 <!-- struts2核心依赖 --> 
 <dependency> 
 <groupId>org.apache.struts</groupId> 
 <artifactId>struts2-core</artifactId> 
 <version>2.3.4</version> 
 <type>jar</type> 
 <scope>compile</scope> 
 </dependency> 
 <!-- struts2零配置依赖 --> 
 <dependency> 
 <groupId>org.apache.struts</groupId> 
 <artifactId>struts2-convention-plugin</artifactId> 
 <version>2.3.4</version> 
 <type>jar</type> 
 <scope>compile</scope> 
 </dependency> 
 <!-- struts2的json依赖 --> 
 <dependency> 
 <groupId>org.apache.struts</groupId> 
 <artifactId>struts2-json-plugin</artifactId> 
 <version>2.3.4</version> 
 <type>jar</type> 
 <scope>compile</scope> 
 </dependency> 
</dependencies>

<?xml version="1.0" encoding="UTF-8"?> 
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"> 
 
 <filter> 
 <filter-name>StrutsPrepareAndExecuteFilter </filter-name> 
 <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter </filter-class> 
 <init-param> 
 <param-name>config</param-name> 
 <param-value>struts-default.xml,struts-plugin.xml,struts.xml</param-value> 
 </init-param> 
 </filter> 
 <filter-mapping> 
 <filter-name>StrutsPrepareAndExecuteFilter</filter-name> 
 <url-pattern>/*</url-pattern> 
 </filter-mapping> 
</web-app> 

<?xml version="1.0" encoding="UTF-8" ?> 
<!DOCTYPE struts PUBLIC 
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" 
"http://struts.apache.org/dtds/struts-2.0.dtd"> 
 
<struts> 
 <package name="base" extends="json-default,struts-default"> 
 <!-- 这里可以设置一些全局的返回值映射关系等 --> 
 </package> 
 
 <constant name="struts.action.extension" value="" /> 
 <constant name="struts.ui.theme" value="simple" /> 
 <constant name="struts.i18n.encoding" value="utf-8" /> 
 <constant name="struts.multipart.maxSize" value="1073741824"/> 
 <constant name="struts.devMode" value="false"/> 
</struts>

package watson.action; 
 
import java.util.HashMap; 
import java.util.Map; 
 
import org.apache.struts2.convention.annotation.Action; 
import org.apache.struts2.convention.annotation.Namespace; 
import org.apache.struts2.convention.annotation.ParentPackage; 
import org.apache.struts2.convention.annotation.Result; 
import org.apache.struts2.convention.annotation.Results; 
 
@ParentPackage("base") 
@Namespace("/watson") 
@Results({ 
 @Result(name = "json",type="json", params={"root","msg"}) 
}) 
public class JsonAction { 
 
 @Action(value="json") 
 public String json() { 
 msg = new HashMap<String, Object>(); 
 msg.put("flag", "success"); 
 
 Map<String, String> user = new HashMap<String, String>(); 
 user.put("name", "张三"); 
 user.put("age", "34"); 
 msg.put("user", user); 
 return "json"; 
 } 
 
 //================================== 
 private Map<String, Object> msg; 
 
 public Map<String, Object> getMsg() { 
 return msg; 
 } 
 
} 

{"flag":"success","user":{"age":"34","name":"张三"}} 

@ParentPackage("base") 
@Namespace("/watson") 
@Results({ 
 @Result(name = "json",type="json", params={"root","msg"}) 
})

<result type="json"> 
 <!-- 这里指定将被Struts2序列化的属性，该属性在action中必须有对应的getter方法 --> 
 <!-- 默认将会序列所有有返回值的getter方法的值，而无论该方法是否有对应属性 --> 
 <param name="root">dataMap</param> 
 <!-- 指定是否序列化空的属性 --> 
 <param name="excludeNullProperties">true</param> 
 <!-- 这里指定将序列化dataMap中的那些属性 --> 
 <param name="includeProperties">userList.*</param> 
 <!-- 这里指定将要从dataMap中排除那些属性，这些排除的属性将不被序列化，一般不与上边的参数配置同时出现 --> 
 <param name="excludeProperties">SUCCESS</param> 
</result>