Java tutorial
package ser423.client; import java.io.*; import java.util.*; import java.net.URL; import org.json.JSONObject; import org.json.JSONArray; /** * Copyright (c) 2014 Tim Lindquist, * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * <p/> * Purpose: This class is part of an example developed for the mobile * computing class at ASU Poly. The application provides a calculator service. * The client and service are both written in Java and they * communicate using JSON-RPC. * <p/> * The Caclulator interface provides the method definitions used by the client * and implemented by the calculator service. * * @author Tim Lindquist * @version 2/1/2015 **/ public class CalcJavaClient extends Object { public String serviceURL; public JsonRpcRequestViaHttp server; public static int id = 0; public CalcJavaClient(String serviceURL) { this.serviceURL = serviceURL; try { this.server = new JsonRpcRequestViaHttp(new URL(serviceURL)); } catch (Exception ex) { System.out.println("Malformed URL " + ex.getMessage()); } } private String packageCalcCall(String oper, double left, double right) { JSONObject jsonObj = new JSONObject(); /* * the following code to create the array should, but does not work correctly * for doubles that are whole numbers. * That is, for + 2.0 3.0 it produces the json array [2,3] * To make the server see double/float values, roll my own to get [2.00,3.00] * This has the disadvantage that it removes any more than two places of accuracy, * but hey, its an class example. JSONArray anArr = new JSONArray(); anArr.put(left); anArr.put(right); jsonObj.put("params",anArr); */ jsonObj.put("jsonrpc", "2.0"); jsonObj.put("method", oper); jsonObj.put("id", ++id); String almost = jsonObj.toString(); String toInsert = ",\"params\":[" + String.format("%.2f", left) + "," + String.format("%.2f", right) + "]"; String begin = almost.substring(0, almost.length() - 1); String end = almost.substring(almost.length() - 1); String ret = begin + toInsert + end; return ret; } /** * Add two numbers * @return The sum */ public double add(double left, double right) { double result = 0; try { String jsonStr = this.packageCalcCall("add", left, right); //System.out.println("sending: "+jsonStr); String resString = server.call(jsonStr); //System.out.println("got back: "+resString); JSONObject res = new JSONObject(resString); result = res.optDouble("result"); } catch (Exception ex) { System.out.println("exception in rpc call to plus: " + ex.getMessage()); } return result; } /** * Subtract two numbers * @return The difference */ public double subtract(double left, double right) { double result = 0; try { String jsonStr = this.packageCalcCall("subtract", left, right); String resString = server.call(jsonStr); JSONObject res = new JSONObject(resString); result = res.optDouble("result"); } catch (Exception ex) { System.out.println("exception in rpc call to plus: " + ex.getMessage()); } return result; } /** * Multiply two numbers * @return The product */ public double multiply(double left, double right) { double result = 0; try { String jsonStr = this.packageCalcCall("multiply", left, right); String resString = server.call(jsonStr); JSONObject res = new JSONObject(resString); result = res.optDouble("result"); } catch (Exception ex) { System.out.println("exception in rpc call to plus: " + ex.getMessage()); } return result; } /** * Divide two numbers * @return left / right */ public double divide(double left, double right) { double result = 0; try { String jsonStr = this.packageCalcCall("divide", left, right); String resString = server.call(jsonStr); JSONObject res = new JSONObject(resString); result = res.optDouble("result"); } catch (Exception ex) { System.out.println("exception in rpc call to plus: " + ex.getMessage()); } return result; } /** * Get the service information. * @return The service information */ public String serviceInfo() { return "Service information"; } public static void main(String args[]) { try { String url = "http://127.0.0.1:8080/"; if (args.length > 0) { url = args[0]; } CalcJavaClient cjc = new CalcJavaClient(url); BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in)); System.out.print("Enter end or {+|-|*|/} double double eg + 3 5 >"); String inStr = stdin.readLine(); StringTokenizer st = new StringTokenizer(inStr); String opn = st.nextToken(); while (!opn.equalsIgnoreCase("end")) { if (opn.equalsIgnoreCase("+")) { double result = cjc.add(Double.parseDouble(st.nextToken()), Double.parseDouble(st.nextToken())); System.out.println("response: " + result); } else if (opn.equalsIgnoreCase("-")) { double result = cjc.subtract(Double.parseDouble(st.nextToken()), Double.parseDouble(st.nextToken())); System.out.println("response: " + result); } else if (opn.equalsIgnoreCase("*")) { double result = cjc.multiply(Double.parseDouble(st.nextToken()), Double.parseDouble(st.nextToken())); System.out.println("response: " + result); } else if (opn.equalsIgnoreCase("/")) { double result = cjc.divide(Double.parseDouble(st.nextToken()), Double.parseDouble(st.nextToken())); System.out.println("response: " + result); } System.out.print("Enter end or {+|-|*|/} double double eg + 3 5 >"); inStr = stdin.readLine(); st = new StringTokenizer(inStr); opn = st.nextToken(); } } catch (Exception e) { System.out.println("Oops, you didn't enter the right stuff"); } } }