text-extend.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE Map>
<Map background-color="white">

    <Parameters>
        <Parameter name="sizes">512, 512</Parameter>
        <Parameter name="bbox">0, 0, 50, 50</Parameter>
    </Parameters>

    <Style name="style">
        <Rule>
            <LineSymbolizer
                stroke-width="5"
                stroke="red"
                />
            <TextSymbolizer
                size="20"
                face-name="DejaVu Sans Book"
                placement="line"
                allow-overlap="true"
                extend="1000"
                max-char-angle-delta="0"
                >
                "label on extended geometry"
            </TextSymbolizer>
            <TextSymbolizer
                size="20"
                face-name="DejaVu Sans Book"
                placement="line"
                allow-overlap="true"
                extend="1000"
                max-char-angle-delta="0"
                dy="-20"
                smooth="0.1"
                >
                "label on extended geometry"
            </TextSymbolizer>
            <TextSymbolizer
                size="20"
                face-name="DejaVu Sans Book"
                placement="line"
                allow-overlap="true"
                extend="1000"
                max-char-angle-delta="0"
                dy="20"
                smooth="1"
                >
                "label on extended geometry"
            </TextSymbolizer>
        </Rule>
    </Style>

    <Layer name="layer">
        <StyleName>style</StyleName>
        <Datasource>
            <Parameter name="type">csv</Parameter>
            <Parameter name="inline">
                wkt
                "LINESTRING(28.9599609375 33.490100708569614,33.7060546875 30.81168525298968,37.4853515625 33.85581940594627)"
                "LINESTRING(23.4228515625 14.75788519200686,27.3779296875 18.29612241175095,30.9814453125 14.162143165417262,35.1123046875 18.29612241175095)"
                "LINESTRING(7.7783203125 33.78280015303917,8.3056640625 26.415486559029276)"
            </Parameter>
        </Datasource>
    </Layer>

</Map>