项目实训10——有join条件的select

1.前端完善

前端增加join关系输入框，并且只有在选择select的时候才显示到页面上。效果如下：

新增变量代表是否选择select

data（）{isSelect：false
}

单选组添加isSelect响应改变方法@change=“changeType”

<el-radio-group v-model="ruleForm.type" @change="changeType"><el-radio label="insert">el-radio><el-radio label="select">el-radio>
el-radio-group>

changeType(val){if(val === 'select'){this.isSelect = true;}else {this.isSelect = false;}
}

join关系输入框通过v-if显示或隐藏

<el-form-item label="join关系" v-if="this.isSelect === true"><el-input style="width: 800px" size="large" v-model="ruleForm.relation" >el-input>
el-form-item>

2.JSON格式添加字段

添加flag字段表示是否有join条件，添加join字段保存join条件。示例如下：

{"dbname":"student","chartsname":["tijian","HHA"],"metas":{"tijian":{"id":"int","sid":"int","des":"string"},
"HHA":{"SS":"TINYINT"}},"type":"select","key":"这里需填写密钥","flag":true,"join":"hh=hh"}

3.后端处理

public List<List<Object>> selectDataJ(String text){UserJson userJson = JSONObject.parseObject(text,UserJson.class);List<List<Object>> result = new ArrayList<>();List<Object> lm = new ArrayList<>();//生成excel的列名String str = "";//select ?String cnames = "";//from ?String condition = userJson.getJoin();//where？for (List<PDetail> pDetails : this.chartnames2) {for (PDetail pDetail : pDetails) {lm.add(pDetail.getChartname() + "." + pDetail.getMeta());str += pDetail.getChartname() + "." + pDetail.getMeta() + ",";}}result.add(lm);for (String s : this.chartnames1) {cnames += s +",";}str = str.substring(0,str.length()-1);cnames = cnames.substring(0,cnames.length()-1);Connection conn = null;PreparedStatement psmt = null;ResultSet rs = null;String jdbcUrl = "jdbc:mysql://localhost:3306/"+this.dbname+"?useSSL=false&serverTimezone=UTC";try {Class.forName("com.mysql.cj.jdbc.Driver");//————————————————————————————————————————————————————————————————//创建连接conn = DriverManager.getConnection(jdbcUrl,"root","jiamohan@599");//——————————————————————————String sql = "SELECT " + str + " FROM " + cnames + " WHERE " + condition;System.out.println(sql);psmt = conn.prepareStatement(sql);rs = psmt.executeQuery();while (rs.next()){List<Object> data = new ArrayList<>();for (Object o : lm) {data.add(rs.getString(o.toString()));}result.add(data);}}catch (Exception e){e.printStackTrace();}finally {try {rs.close();psmt.close();conn.close();} catch (SQLException e){e.printStackTrace();}}return result;}

4.效果展示

本文来自互联网用户投稿，文章观点仅代表作者本人，不代表本站立场，不承担相关法律责任。如若转载，请注明出处。 如若内容造成侵权/违法违规/事实不符，请点击【内容举报】进行投诉反馈！