Java Servlet和Raspberry Pi IO
[英]Java Servlets and Raspberry Pi IO
问题描述
I'm trying to learn how to write simple servlets to use with a Raspberry Pi. 
我正在尝试学习如何编写与Raspberry Pi一起使用的简单servlet。 I want to control the board I/O via web.I'm using the Pi4J library which is a wrapper for the WiringPi C library.It works when I use it to blink a led locally so I assume that I'm doing something wrong coding my servlet. 我想通过Web控制板卡的I / O，我使用的是Pi4J库，它是WiringPi C库的包装器，当我使用它来本地闪烁LED时它可以工作，所以我认为我做错了编码我的servlet。
This is the code I wrote: 这是我写的代码：
package com.luca.servlet;
import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalOutput;
import com.pi4j.io.gpio.RaspiPin;
import com.pi4j.io.gpio.PinState;
public class MyServlet extends javax.servlet.http.HttpServlet {
private GpioController gpio=GpioFactory.getInstance();
private GpioPinDigitalOutput redLed=gpio.provisionDigitalOutputPin(RaspiPin.GPIO_23,PinState.LOW);
private GpioPinDigitalOutput greenLed=gpio.provisionDigitalOutputPin(RaspiPin.GPIO_22,PinState.LOW);
private GpioPinDigitalOutput blueLed=gpio.provisionDigitalOutputPin(RaspiPin.GPIO_21,PinState.LOW);
private GpioPinDigitalOutput[] pins=new GpioPinDigitalOutput[]{redLed,greenLed,blueLed};
@Override
public void doGet(javax.servlet.http.HttpServletRequest request,javax.servlet.http.HttpServletResponse response) throws java.io.IOException {
java.io.PrintWriter print=response.getWriter();
print.write("<body>"+
"<p> Choose a color! </p>"+
"<form action=\"first\" method=\"POST\">"+
"<input type=\"submit\" name=\"button\" value=\"red\"/>"+
"</form>"+
"<form action=\"first\" method=\"POST\">"+
"<input type=\"submit\" name=\"button\" value=\"green\"/>"+
"</form>"+
"<form action=\"first\" method=\"POST\">"+
"<input type=\"submit\" name=\"button\" value=\"blue\"/>"+
"</form>"+
"</body>");
}
public void doPost(javax.servlet.http.HttpServletRequest request,javax.servlet.http.HttpServletResponse response) throws java.io.IOException {
java.io.PrintWriter pw=response.getWriter();
String act=request.getParameter("button");
switch(act) {
case "red":
togglePin();
redLed.high();
pw.write("<p>the led is red!</p>");
break;
case "green":
togglePin();
greenLed.high();
pw.write("<p>the led is green</p>");
break;
case "blue":
togglePin();
blueLed.high();
pw.write("<p>the led is blue!</p>");
break;
}
}
private void togglePin() {
for (GpioPinDigitalOutput pin : pins)
if (pin.isHigh()) pin.toggle();
}
it compiles fine and I manually deploy it inside tomcat,with the deployment descriptor and all. 它编译良好，我将其与部署描述符及所有内容手动部署在tomcat中。 But when I connect it says to me that the resource is unavailable. 但是当我连接时，它告诉我该资源不可用。 If I remove the GPIO related code it works fine. 如果我删除与GPIO相关的代码，则可以正常工作。
Can someone please help me out? 有人可以帮我吗？ Google searching doesn't seem to help Google搜索似乎没有帮助
2 个解决方案
解决方案1
0 2015-12-08 15:28:05
You need to set an Url Pattern in order to access to your servlet methods like POST and GET . 您需要设置一个Url Pattern才能访问POST和GET之类的servlet方法。
For example use: 例如使用：
@WebServlet("/raspberryServelt")
public class MyServlet extends javax.servlet.http.HttpServlet {
...
And then access to the servlet methods doing a POST or GET request... 然后访问执行POST或GET请求的servlet方法...
For example doing a get to: 例如，进行以下操作：
localhost:8080/yourWebAppName/raspberryServelt
Will work... 将工作...
解决方案2
0 2017-04-01 21:10:48
您必须将pi4j库放在项目WEB-INF / lib中
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