1.查看小程序api生成二维码，小程序码（有a,b,c等多种方式）

2.通过百度查找java小程序码搜索

3.搭建测试环境测试demo案例

注意事项:上述涉及到的appid和秘钥是小程序的非公众号的

接口B：适用于需要的码数量极多，或仅临时使用的业务场景

接口地址：

https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=ACCESS_TOKEN

获取 access_token 详见文档

POST 参数说明

注意：通过该接口生成的小程序码，永久有效，数量暂无限制。用户扫描该码进入小程序后，开发者需在对应页面获取的码中 scene 字段的值，再做处理逻辑。使用如下代码可以获取到二维码中的 scene 字段的值。调试阶段可以使用开发工具的普通编译下拉（添加编译模式）自定义参数 scene=xxxx 进行模拟，开发工具模拟时的 scene 的参数值需要进行 urlencode

// 这是首页的 js
Page({
  onLoad: function(options) {
    // options 中的 scene 需要使用 decodeURIComponent 才能获取到生成二维码时传入的 scene
    var scene = decodeURIComponent(options.scene)
  }
})

java源码（main方法生成小程序码）

package com.zw.xcx;

import org.springframework.http.HttpEntity;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.client.RestTemplate;

import java.util.HashMap;
import java.util.Map;
import net.sf.json.JSONObject;
import redis.clients.jedis.Jedis;

import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class TestPost {

public static void main(String[] args) throws Exception {
// TODO 自动生成的方法存根

GetUrl();
Jedis jedis = new Jedis("localhost");
String access_token = jedis.get("access_token");
System.out.println("access_token is:"+access_token);
getminiqrQr("0736",access_token);
}

public static void GetUrl() throws ClientProtocolException,
IOException {
HttpGet httpGet = new HttpGet(
"https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid="
+ Xcx.APPID + "&secret="
+ Xcx.SECRET );
HttpClient httpClient = HttpClients.createDefault();
HttpResponse res = httpClient.execute(httpGet);
org.apache.http.HttpEntity entity = res.getEntity();
String result = EntityUtils.toString(entity, "UTF-8");
JSONObject jsons = JSONObject.fromObject(result);
String expires_in = jsons.getString("expires_in");

//缓存
if(Integer.parseInt(expires_in)==7200){
//ok
String access_token = jsons.getString("access_token");
Jedis cache = new Jedis("127.0.0.1", 6379);
System.out.println("access_token:"+access_token);
Pipeline pipeline = cache.pipelined();
pipeline.set("access_token", access_token);
pipeline.expire("access_token", 7200);
pipeline.sync();
}else{
System.out.println("出错获取token失败！");
}

}

public static String GetPostUrl(String access_token,String id) throws Exception {
System.out.println(access_token);
System.out.println(id);
String url ="https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token=";
Map<String, Object> map = new HashMap<String, Object>();
map.put("scene", "0736");//你二维码中跳向的地址
map.put("page", "pages/index/index");//你二维码中跳向的地址
map.put("width", "430");//图片大小
JSONObject json = JSONObject.fromObject(map);
System.out.println(json);
return null;
}


public static Map getminiqrQr(String sceneStr, String accessToken) {
RestTemplate rest = new RestTemplate();
InputStream inputStream = null;
OutputStream outputStream = null;
try {
String url = "https://api.weixin.qq.com/wxa/getwxacodeunlimit?access_token="+accessToken;
Map<String,Object> param = new HashMap<>();
param.put("scene", sceneStr);
param.put("page", "pages/index/index");
param.put("width", 430);
param.put("auto_color", false);
Map<String,Object> line_color = new HashMap<>();
line_color.put("r", 0);
line_color.put("g", 0);
line_color.put("b", 0);
param.put("line_color", line_color);
MultiValueMap<String, String> headers = new LinkedMultiValueMap<>();
HttpEntity requestEntity = new HttpEntity(param, headers);
ResponseEntity<byte[]> entity = rest.exchange(url, HttpMethod.POST, requestEntity, byte[].class, new Object[0]);
byte[] result = entity.getBody();
inputStream = new ByteArrayInputStream(result);

File file = new File("D://erweima/"+sceneStr+".png");
if (!file.exists()){
file.createNewFile();
}
outputStream = new FileOutputStream(file);
int len = 0;
byte[] buf = new byte[1024];
while ((len = inputStream.read(buf, 0, 1024)) != -1) {
outputStream.write(buf, 0, len);
}
outputStream.flush();
} catch (Exception e) {
} finally {
if(inputStream != null){
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(outputStream != null){
try {
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
}

替换小程序码中间图片

package com.zw.xcx;

import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;

import javax.imageio.ImageIO;

public class TestImageChange {

public static void main(String[] args)
{
try
{
BufferedImage appletImg = ImageIO.read(new FileInputStream("D://erweima/applet.png"));
Graphics2D g2d = appletImg.createGraphics();

// 设置抗锯齿的属性
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);

BufferedImage centerImg = ImageIO.read(new File("D://erweima/center.png"));
g2d.drawImage(centerImg.getScaledInstance(centerImg.getWidth(), centerImg.getHeight(), Image.SCALE_SMOOTH), (appletImg.getWidth() - centerImg.getWidth()) / 2, (appletImg.getHeight() - centerImg.getHeight()) / 2, null);

// 关闭资源
g2d.dispose();
ImageIO.write(appletImg, "png", new File("D://erweima/newApplet.png"));
}
catch (Exception e)
{
e.printStackTrace();
}
}


}