Stream result type是Struts2中比较有用的一个feature。特别是在动态生成图片和文档的情况下；例如动态验证码，各种报表图片生成等。鉴于网上使用struts2生成动态验证码，struts2+jfreechart的例子中很少使用到该feature，这里以生成动态验证码为例解释stream result的使用：
Action类，action主要要提供一个获取InputStrem的方法Java代码
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;
}
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Java代码
<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>
<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>
可以看出使用Stream result type非常简单。在该例子中使用了一个小技巧将OutputStream转化为InputStremJava代码
ByteArrayOutputStream output = new ByteArrayOutputStream();
//省略填充output的代码
...
InputStrem
in = new ByteArrayInputStream(output.toByteArray());
