怎麼讓圖中X軸顯示2015/2016/2017echarts 柱状配置项内容和展示

怎麼讓圖中X軸顯示2015/2016/2017?

      option = {
    legend: {},
    tooltip: {},
    xAxis: [
        {type: 'category', gridIndex: 0, boundaryGap: true, axisLabel: { rotate: 0, interval: 0 }},
        {type: 'category', gridIndex: 1, boundaryGap: true, axisLabel: { rotate: 0, interval: 0 }},
    ],
    yAxis: [{ gridIndex: 0, type: 'value', },
            { gridIndex: 1, type: 'value' }],
    grid: [
        {bottom: '55%'},
        {top: '55%'}
    ],
    dataset: {
        dimensions: ['product','2015', '2016', '2017'],
        source: [
                    { product: 'Matcha Latte', '2015': 43.3, '2016': 85.8, '2017': 93.7 },
                    { product: 'Milk Tea', '2015': 83.1, '2016': 73.4, '2017': 55.1 },
                    { product: 'Cheese Cocoa', '2015': 86.4, '2016': 65.2, '2017': 82.5 },
                    { product: 'Walnut Brownie', '2015': 72.4, '2016': 53.9, '2017': 39.1 }
                ]
    },
    series: [
        // 这几个系列会在第一个直角坐标系中，每个系列对应到 dataset 的每一行。
        {type: 'bar', seriesLayoutBy: 'row'},
        {type: 'bar', seriesLayoutBy: 'row'},
        {type: 'bar', seriesLayoutBy: 'row'},
        // 这几个系列会在第二个直角坐标系中，每个系列对应到 dataset 的每一列。
        {type: 'bar', xAxisIndex: 1, yAxisIndex: 1},
        {type: 'bar', xAxisIndex: 1, yAxisIndex: 1},
        {type: 'bar', xAxisIndex: 1, yAxisIndex: 1},
        {type: 'bar', xAxisIndex: 1, yAxisIndex: 1}
    ]
}