【Struts2】result类型

Struts2 result类型

1.dispatcher：服务器跳转到页面，通常来处理JSP，默认类型。

2.redirect：重定向到页面。

Action：

1 public String redirect() {
2         message = "message中有值";
3         return "redirect";
4 }  

struts.xml

1 <package name="chapter3" namespace="/chapter3" extends="struts-default">
2         <action name="redirectAction" class="chapter3.action.Chapter3Action" method="redirect">
3             <result name="redirect" type="redirect">/redirect.jsp</result>
4         </action>
5 </package>  

注意的地方:外部中转不能带值过去,并且页面不能受保护

传参数:

1 <action name="redirectAction" class="chapter3.action.Chapter3Action" method="redirect">
2     <result name="redirect" type="redirect">/redirect.jsp?message=${message}</result>
3 </action>  

页面:

${param.message}<br>

3.chain：服务端跳转到Action；

action:

1 public String action2() {
2     message = "我是action2中设置的值";
3     return "action2";
4 }  

struts.xml

1 <package name="chapter32" namespace="/chapter32" extends="struts-default">
2     <action name="action2" class="chapter3.action.Chapter3Action" method="action2">
3         <result name="action2" type="chain">
4             <param name="actionName">redirectAction</param>
5             <param name="namespace">/chapter3</param>
6         </result>
7     </action>
8 </package>  

4.redirectAction：外部跳转到Action；

action:

1 public String action3() {
2     message = "我是action3中设置的值";
3     return "action3";
4 }  

struts.xml

1 <action name="action3" class="chapter3.action.Chapter3Action" method="action3">
2     <result name="action3" type="redirectAction">redirectAction</result>
3 </action>  

跨命名空间的外部跳转:

1 public String action4() {
2     message = "我是action4中设置的值";
3     return "action4";
4 }  

struts.xml

1 <action name="action4" class="chapter3.action.Chapter3Action" method="action4">
2     <result name="action4" type="redirectAction">
3         <param name="actionName">redirectAction</param>
4         <param name="namespace">/chapter3</param>
5     </result>
6 </action>  

5，json

Struts2中返回JSON的格式有两种，一种是使用Servelt输出流，另一种就是使用struts2对JSON的扩展。这里笔者介绍第一种，

编写Action代码：

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();
}

配置Action:

从以下的配置中可以明显的看到配置与普通的action配置没有任何区别，只是没有返回的视图而已。

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

返回值：

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

6，stream

就是把数据以字节流的方式输出，

1：图片验证码：

Action类，action主要要提供一个获取InputStrem的方法：

public class CheckCodeAction extends ActionSupport implements SessionAware {
private Logger log = LoggerFactory.getLogger(this.getClass());
private InputStream imageStream;
private Map session;

public String getCheckCodeImage(String str, int show, ByteArrayOutputStream output) {
Random random = new Random();
BufferedImage image = new BufferedImage(80, 30, BufferedImage.TYPE_3BYTE_BGR);
Font font = new Font("Arial", Font.PLAIN, 24);
int distance = 18;
Graphics d = image.getGraphics();
d.setColor(Color.WHITE);
d.fillRect(0, 0, image.getWidth(), image.getHeight());
d.setColor(new Color(random.nextInt(100) + 100, random.nextInt(100) + 100, random.nextInt(100) + 100));
for (int i = 0; i < 10; i++) {
d.drawLine(random.nextInt(image.getWidth()), random.nextInt(image.getHeight()), random.nextInt(image.getWidth()),
random.nextInt(image.getHeight()));
}
d.setColor(Color.BLACK);
d.setFont(font);
String checkCode = "";
char tmp;
int x = -distance;
for (int i = 0; i < show; i++) {
tmp = str.charAt(random.nextInt(str.length() - 1));
checkCode = checkCode + tmp;
x = x + distance;
d.setColor(new Color(random.nextInt(100) + 50, random.nextInt(100) + 50, random.nextInt(100) + 50));
d.drawString(tmp + "", x, random.nextInt(image.getHeight() - (font.getSize())) + (font.getSize()));
}
d.dispose();
try {
ImageIO.write(image, "jpg", output);
} catch (IOException e) {
log.warn("生成验证码错误.", e);
}
return checkCode;
}

public String execute() throws Exception {
ByteArrayOutputStream output = new ByteArrayOutputStream();
String checkCode = getCheckCodeImage("ABCDEFGHJKLMNPQRSTUVWXYZ123456789", 4, output);
this.session.put(Constants.CHECK_CODE_KEY, checkCode);
//这里将output stream转化为 inputstream
this.imageStream = new ByteArrayInputStream(output.toByteArray());
output.close();
return SUCCESS;
}

public InputStream getImageStream() {
return imageStream;
}

public void setSession(Map session) {
this.session = session;
}

struts配置文件：

<action name="checkCode" class="CheckCodeAction">
<result name="success" type="stream">
<param name="contentType">image/jpeg</param>
<!-- 指定提供InputStream的filed name -->
<param name="inputName">imageStream</param>
<param name="bufferSize">1024</param>
</result>
<interceptor-ref name="defaultStack"/>
</action>

原文链接：http://www.cnblogs.com/elleniou/archive/2012/10/17/2728237.html