记录一次solr自定义函数编写及使用的过程

import org.apache.commons.lang.StringUtils;
import org.apache.lucene.queries.function.ValueSource;
import org.apache.solr.schema.SchemaField;
import org.apache.solr.search.FunctionQParser;
import org.apache.solr.search.SyntaxError;
import org.apache.solr.search.ValueSourceParser;
public class SubStrValueSourceParser extends ValueSourceParser {
    public SubStrValueSourceParser() {
        super();
    }
    @Override
    public ValueSource parse(FunctionQParser fp) throws SyntaxError {
        String fieldStr = fp.parseArg();//第一个参数
        String bgnLocation = fp.parseArg();//第二个参数数组下标
        ValueSource location = getValueSource(fp, fieldStr);//取得函数调用时指定字段值
//将参数及需要的文档的值传给自定义的ValueSource方法，打分规则在自定义的ValueSource中定制
        SubStrValueSource stringFieldSource = new SubStrValueSource(location, bgnLocation);
        return stringFieldSource;
    }
//该方法是根据字段名，从FunctionQParser得到文档该字段的相关信息
    public ValueSource getValueSource(FunctionQParser fp, String arg) {
        if (arg == null)
            return null;
        SchemaField f = fp.getReq().getSchema().getField(arg);
        return f.getType().getValueSource(f, fp);
    }
}

import org.apache.commons.lang.StringUtils;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.queries.function.FunctionValues;
import org.apache.lucene.queries.function.ValueSource;
import org.apache.lucene.queries.function.docvalues.DoubleDocValues;
import org.apache.lucene.queries.function.docvalues.FloatDocValues;
import org.apache.lucene.queries.function.docvalues.IntDocValues;
import org.apache.lucene.queries.function.docvalues.StrDocValues;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;
import java.io.IOException;
import java.util.List;
import java.util.Map;
public class SubStrValueSource extends ValueSource {
    private ValueSource attr13;//需要进行格式转换的字段
    private String location;
    //通过构造方法获取字段
    public SubStrValueSource(ValueSource attr13, String location) {
        this.attr13 = attr13;
        this.location = location;
    }
    @Override
    public FunctionValues getValues(Map map, LeafReaderContext leafReaderContext) throws IOException {
        final FunctionValues fieldValues = attr13.getValues(map,
                leafReaderContext);//获取attr13的值
        return new DoubleDocValues(this) {
            @Override
            public double doubleVal(int i) throws IOException {
                String fieldStr = null;
                Double retValue = 0.00;
                //若要被转化的值为空或者为空字符串则返回0
                if (fieldValues.strVal(i) == null || "".equals(fieldValues.strVal(i))) {
                } else {
                    fieldStr = fieldValues.strVal(i);
                    String[] vList = fieldStr.split(",");
                    //若实际数组长度小于下标则不处理直接返回0，若大于或等于下标则截取对应位置数据
                    if (vList.length < Integer.parseInt(location) + 1) {
                    } else {
                        String content = vList[Integer.parseInt(location)];
                        retValue = Double.parseDouble(content);
                    }
                }
                return retValue;
            }
        };
    }
    @Override
    public boolean equals(Object o) {
        return true;
    }
    @Override
    public int hashCode() {
        return 0;
    }
    @Override
    public String description() {
        return name();
    }
    public String name() {
        return "subStr";
    }
}