如何构建一个矢量瓦片服务

// Pixel size (to calculate scales). The default is 0.28mm/pixel, corresponding to 90.71428571428572 DPI.
public static GridSet buildGriDSet(SRS srs, double pixelSize) {
    return GridSetFactory.createGridSet(String.valueOf(srs.getNumber()), srs, BoundingBox.WORLD3857, false, 30, null,
            pixelSize, 256, 256, false);
}
// 需要将其转换为米
buildGriDSet(SRS.getEPSG900913(), 0.00028D);

public static GridSet createGridSet(String name, SRS srs, BoundingBox extent, boolean alignTopLeft, int levels, Double metersPerUnit, double pixelSize, int tileWidth, int tileHeight, boolean yCoordinateFirst) {
    double extentWidth = extent.getWidth();
    double extentHeight = extent.getHeight();
    double resX = extentWidth / (double)tileWidth;
    double resY = extentHeight / (double)tileHeight;
    int tilesWide;
    int tilesHigh;
    // 计算调整的基数, 以小边为主
    if (resX <= resY) {
        tilesWide = 1;
        tilesHigh = (int)Math.round(resY / resX);
        resY /= (double)tilesHigh;
    } else {
        tilesHigh = 1;
        tilesWide = (int)Math.round(resX / resY);
        resX /= (double)tilesWide;
    }

    // 计算地图分辨率, 即单位像素内表示的地图单位(米或度)
    double res = Math.max(resX, resY);
    // 获取裁减后的范围
    double adjustedExtentWidth = (double)(tilesWide * tileWidth) * res;
    double adjustedExtentHeight = (double)(tilesHigh * tileHeight) * res;
    // 根据上述范围重新构建范围表达
    BoundingBox adjExtent = new BoundingBox(extent);
    adjExtent.setMaxX(adjExtent.getMinX() + adjustedExtentWidth);
    // 这里想要表达的就是原点在于左上角还是左下角（确定起算位置）, 因为这样会影响y方向上的范围计算。就是进行y方向上范围计算
    if (alignTopLeft) {
        adjExtent.setMinY(adjExtent.getMaxY() - adjustedExtentHeight);
    } else {
        adjExtent.setMaxY(adjExtent.getMinY() + adjustedExtentHeight);
    }

    // 根据给定的层级参数, 构建各层级下分辨率值
    double[] resolutions = new double[levels];
    // 设置0级的分辨率
    resolutions[0] = res;

    for(int i = 1; i < levels; ++i) {
        // 采用常规均匀四分（四叉树）方式进行构建
        resolutions[i] = resolutions[i - 1] / 2.0D;
    }

    return createGridSet(name, srs, adjExtent, alignTopLeft, resolutions, (double[])null, metersPerUnit, pixelSize, (String[])null, tileWidth, tileHeight, yCoordinateFirst);
}

public static GridSet createGridSet(String name, SRS srs, BoundingBox extent, boolean alignTopLeft, double[] resolutions, double[] scaleDenoms, Double metersPerUnit, double pixelSize, String[] scaleNames, int tileWidth, int tileHeight, boolean yCoordinateFirst) {
    Assert.notNull(name, "name is null");
    Assert.notNull(srs, "srs is null");
    Assert.notNull(extent, "extent is null");
    Assert.isTrue(!extent.isNull() && extent.isSane(), "Extent is invalid: " + extent);
    Assert.isTrue(resolutions != null || scaleDenoms != null, "The gridset definition must have either resolutions or scale denominators");
    Assert.isTrue(resolutions == null || scaleDenoms == null, "Only one of resolutions or scaleDenoms should be provided, not both");

    int i;
    for(i = 1; resolutions != null && i < resolutions.length; ++i) {
        if (resolutions[i] >= resolutions[i - 1]) {
            throw new IllegalArgumentException("Each resolution should be lower than it's prior one. Res[" + i + "] == " + resolutions[i] + ", Res[" + (i - 1) + "] == " + resolutions[i - 1] + ".");
        }
    }

    for(i = 1; scaleDenoms != null && i < scaleDenoms.length; ++i) {
        if (scaleDenoms[i] >= scaleDenoms[i - 1]) {
            throw new IllegalArgumentException("Each scale denominator should be lower than it's prior one. Scale[" + i + "] == " + scaleDenoms[i] + ", Scale[" + (i - 1) + "] == " + scaleDenoms[i - 1] + ".");
        }
    }

    GridSet gridSet = baseGridSet(name, srs, tileWidth, tileHeight);
    // true：保留分辨率并计算 scaleDenominators
    // false：分辨率是根据 sacale 分母计算的
    gridSet.setResolutionsPreserved(resolutions != null);
    gridSet.setPixelSize(pixelSize);
    gridSet.setOriginalExtent(extent);
    // tileOrigin()的y坐标是在顶部（true）还是在底部（false），相应的标记原点位置
    gridSet.yBaseToggle = alignTopLeft;
    // 轴顺序, 默认经度优先
    gridSet.setyCoordinateFirst(yCoordinateFirst);
    // 设置单位, 每个单位内表示多少米
    // 经纬度直投的情况需要特殊处理
    if (metersPerUnit == null) {
        if (srs.equals(SRS.getEPSG4326())) {
            gridSet.setMetersPerUnit(111319.49079327358D);
        } else if (srs.equals(SRS.getEPSG3857())) {
            gridSet.setMetersPerUnit(1.0D);
        } else {
            if (resolutions == null) {
                log.config("GridSet " + name + " was defined without metersPerUnit, assuming 1m/unit. All scales will be off if this is incorrect.");
            } else {
                log.config("GridSet " + name + " was defined without metersPerUnit. Assuming 1m per SRS unit for WMTS scale output.");
                gridSet.setScaleWarning(true);
            }

            gridSet.setMetersPerUnit(1.0D);
        }
    } else {
        gridSet.setMetersPerUnit(metersPerUnit);
    }

    if (resolutions == null) {
        gridSet.setGridLevels(new Grid[scaleDenoms.length]);
    } else {
        gridSet.setGridLevels(new Grid[resolutions.length]);
    }

    for(i = 0; i < gridSet.getNumLevels(); ++i) {
        Grid curGrid = new Grid();
        if (scaleDenoms != null) {
            curGrid.setScaleDenominator(scaleDenoms[i]);
            curGrid.setResolution(pixelSize * (scaleDenoms[i] / gridSet.getMetersPerUnit()));
        } else {
            curGrid.setResolution(resolutions[i]);
            // 计算比例尺 (单位像素下表示的实际空间距离 * 每个单位情况表示多少米) / (像素大小，或称像元大小)
            // 约去像元, 即获取到比例尺分母
            curGrid.setScaleDenominator(resolutions[i] * gridSet.getMetersPerUnit() / 2.8E-4D);
        }

        double mapUnitWidth = (double)tileWidth * curGrid.getResolution();
        double mapUnitHeight = (double)tileHeight * curGrid.getResolution();
        long tilesWide = (long)Math.ceil((extent.getWidth() - mapUnitWidth * 0.01D) / mapUnitWidth);
        long tilesHigh = (long)Math.ceil((extent.getHeight() - mapUnitHeight * 0.01D) / mapUnitHeight);
        curGrid.setNumTilesWide(tilesWide);
        curGrid.setNumTilesHigh(tilesHigh);
        if (scaleNames != null && scaleNames[i] != null) {
            curGrid.setName(scaleNames[i]);
        } else {
            curGrid.setName(gridSet.getName() + ":" + i);
        }

        gridSet.setGrid(i, curGrid);
    }

    return gridSet;
}