Vue利用js与java实现水印，并且水印内容分两层逐级显示。

1、前端js，代码如下：

let watermark = {}
let setWatermark = (str,str1) => {  
    let id = '1.23452384164.123412416'; 
    if (document.getElementById(id) !== null) {    
        document.body.removeChild(document.getElementById(id)); 
     }  
    //创建一个画布 
    let can = document.createElement('canvas'); 
    //设置画布的长宽 
    can.width = 500; can.height = 220; 
    let cans = can.getContext('2d'); 
    //旋转角度 
    cans.rotate(-15 * Math.PI / 180); 
    //字体大小 
    cans.font = '25px Vedana'; 
    //设置填充绘画的颜色、渐变或者模式 
    cans.fillStyle = 'rgba(200, 200, 200, 0.40)'; 
    //设置文本内容的当前对齐方式 
    cans.textAlign = 'left'; 
    //设置在绘制文本时使用的当前文本基线 
    cans.textBaseline = 'Middle'; 
    //在画布上绘制填色的文本（输出的文本，开始绘制文本的X坐标位置，开始绘制文本的Y坐标位置） 
    cans.fillText(str, can.width / 8, can.height / 2); 
    cans.fillText(str1, can.width / 8, can.height -70,170); 
    let div = document.createElement('div'); 
    div.id = id; 
    div.style.pointerEvents = 'none'; 
    div.style.top = '30px'; 
    div.style.left = '0px'; 
    div.style.position = 'fixed'; 
    div.style.zIndex = '100000'; 
    div.style.width = document.documentElement.clientWidth + 'px'; 
    div.style.height = document.documentElement.clientHeight + 'px'; 
    div.style.whiteSpace = "pre"; 
    div.style.background = 'url(' + can.toDataURL('image/png') + ') left top repeat'; 
    document.body.appendChild(div); 
    return id;
}
// 该方法只允许调用一次
watermark.set = (str,str1) => {  
    let id = setWatermark(str,str1); 
    setInterval(() => {    
    if (document.getElementById(id) === null) {      
    id = setWatermark(str,str1); 
    }  
}, 500); 
   window.onresize = () => {    
    setWatermark(str,str1); 
    };
}
// 在watermark.js文件中
const outWatermark = (id) => {  
    if (document.getElementById(id) !== null) {    
        const div = document.getElementById(id)    
        div.style.display = 'none' 
    }
 }
watermark.out = () => {  
    const str = '1.23452384164.123412416' 
    outWatermark(str)
}
export default watermark;

2、后端编写代码查询当前用户及其上一级

2.1 服务层
public List<Record> selectBySchoolName1(Object roleId) {    
    return dbPro.find("SELECT T2.name \n" +            
                        "FROM ( \n" +            
                        " SELECT \n" +            
                        " @r AS _id, \n" +            
                        " (SELECT @r := pid FROM groupRole WHERE id = _id) AS parent_id, \n" +            
                        " @l := @l + 1 AS lvl \n" +            
                        " FROM \n" +            
                        " (SELECT @r := "+roleId+", @l := 0) vars, \n" +            
                        " groupRole h \n" +            
                        " WHERE @r <> 0) T1 \n" +            
                        "JOIN groupRole T2 \n" +            
                        "ON T1._id = T2.id and T1.parent_id != 0\n" +            
                        "ORDER BY T1.lvl DESC ");
}2.2 控制层
@PostMapping("/selectWatermark")
public JSONObject selectWatermark(@RequestBody JSONObject jsonObject) {    
    String roleId = jsonObject.getString("roleId");//当前角色id 
    List<Record> listAll = new ArrayList<Record>(); 
    Record record = new Record(); 
    List<Record> list = shoppingMallService.selectBySchoolName1(roleId);//根据学校id查询学校 
    String watermarkSchool = " "; 
    for (int i = 0; i < list.size(); i++) {        
        watermarkSchool += list.get(i).getStr("name"); 
        record.set("schoolName", watermarkSchool); 
    }    
    listAll.add(record); 
    setAttr("list", listAll); return resultSuccess();
}

3.前端调用接口，并将查询的数据存入localStorage

vueWatermark(id){  
    this.axiosPost("shoppingMall/selectWatermark",{    roleId: id,//当前用户角色id 
    },function (res) {    
        localStorage.setItem("watermarkName", res.list[0].schoolName); 
        })
},

4.需要水印的页面调用js并传入存到localStorage中的值

Watermark.set(localStorage.getItem("watermarkName"), localStorage.getItem("loginUserName") + "\n" + localStorage.getItem("loginUserPhone"));

至此，水印功能实现完毕。