和我一起打造个简单搜索之SpringDataElasticSearch关键词高亮

前面几篇文章详细讲解了 ElasticSearch 的搭建以及使用 SpringDataElasticSearch 来完成搜索查询，但是搜索一般都会有搜索关键字高亮的功能，今天我们把它给加上。

系列文章

环境依赖

本文以及后续 es 系列文章都基于 5.5.3 这个版本的 elasticsearch ，这个版本比较稳定，可以用于生产环境。

SpringDataElasticSearch 的基本使用可以看我的上一篇文章和我一起打造个简单搜索之SpringDataElasticSearch入门，本文就不再赘述。

高亮关键字实现

前文查询是通过写一个接口来继承 ElasticsearchRepository 来实现的，但是如果要实现高亮，我们就不能这样做了，我们需要使用到 ElasticsearchTemplate来完成。

查看这个类的源码

public class ElasticsearchTemplate implements ElasticsearchOperations, ApplicationContextAware {
    ...
}

可以看到，ElasticsearchTemplate 实现了接口 ApplicationContextAware，所以这个类是被 Spring 管理的，可以在类里面直接注入使用。

代码如下:

@Slf4j
@Component
public class HighlightBookRepositoryTest extends EsSearchApplicationTests {

    @Autowired
    private ElasticsearchTemplate elasticsearchTemplate;
    @Resource
    private ExtResultMapper extResultMapper;

    @Test
    public void testHighlightQuery() {
        BookQuery query = new BookQuery();
        query.setQueryString("穿越");

        // 复合查询
        BoolQueryBuilder boolQuery = QueryBuilders.boolQuery();

        // 以下为查询条件, 使用 must query 进行查询组合
        MultiMatchQueryBuilder matchQuery = QueryBuilders.multiMatchQuery(query.getQueryString(), "name", "intro", "author");
        boolQuery.must(matchQuery);

        PageRequest pageRequest = PageRequest.of(query.getPage() - 1, query.getSize());

        NativeSearchQuery searchQuery = new NativeSearchQueryBuilder()
                .withQuery(boolQuery)
                .withHighlightFields(
                        new HighlightBuilder.Field("name").preTags("<span style=\"color:red\">").postTags("</span>"),
                        new HighlightBuilder.Field("author").preTags("<span style=\"color:red\">").postTags("</span>"))
                .withPageable(pageRequest)
                .build();
        Page<Book> books = elasticsearchTemplate.queryForPage(searchQuery, Book.class, extResultMapper);

        books.forEach(e -> log.info("{}", e));
        // <span style="color:red">穿越</span>小道人
    }
}

注意这里的

 Page<Book> books = elasticsearchTemplate.queryForPage(searchQuery, Book.class, extResultMapper);

这里返回的是分页对象。
查询方式和上文的差不多，只不过是是 Repository 变成了 ElasticsearchTemplate，操作方式也大同小异。

这里用到了 ExtResultMapper，请接着看下文。

自定义ResultMapper

ResultMapper 是用于将 ES 文档转换成 Java 对象的映射类，因为 SpringDataElasticSearch 默认的的映射类 DefaultResultMapper 不支持高亮，因此，我们需要自己定义一个 ResultMapper。

复制 DefaultResultMapper 类，重命名为 ExtResultMapper，对构造方法名称修改为正确的值。

新增一个方法，用于将高亮的内容赋值给需要转换的 Java 对象内。

在 mapResults 方法内调用这个方法。

注意：这个类可以直接拷贝到你的项目中直接使用！
我写这么多，只是想说明为什么这个类是这样的。

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import org.apache.commons.beanutils.PropertyUtils;
import org.elasticsearch.action.get.GetResponse;
import org.elasticsearch.action.get.MultiGetItemResponse;
import org.elasticsearch.action.get.MultiGetResponse;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.common.text.Text;
import org.elasticsearch.search.SearchHit;
import org.elasticsearch.search.SearchHitField;
import org.elasticsearch.search.fetch.subphase.highlight.HighlightField;
import org.springframework.data.domain.Pageable;
import org.springframework.data.elasticsearch.ElasticsearchException;
import org.springframework.data.elasticsearch.annotations.Document;
import org.springframework.data.elasticsearch.annotations.ScriptedField;
import org.springframework.data.elasticsearch.core.AbstractResultMapper;
import org.springframework.data.elasticsearch.core.DefaultEntityMapper;
import org.springframework.data.elasticsearch.core.EntityMapper;
import org.springframework.data.elasticsearch.core.aggregation.AggregatedPage;
import org.springframework.data.elasticsearch.core.aggregation.impl.AggregatedPageImpl;
import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentEntity;
import org.springframework.data.elasticsearch.core.mapping.ElasticsearchPersistentProperty;
import org.springframework.data.mapping.context.MappingContext;
import org.springframework.stereotype.Component;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.nio.charset.Charset;
import java.util.*;

/**
 * 类名称：ExtResultMapper
 * 类描述：自定义结果映射类
 * 创建人：WeJan
 * 创建时间：2018-09-13 20:47
 */
@Component
public class ExtResultMapper extends AbstractResultMapper {

    private MappingContext<? extends ElasticsearchPersistentEntity<?>, ElasticsearchPersistentProperty> mappingContext;

    public ExtResultMapper() {
        super(new DefaultEntityMapper());
    }

    public ExtResultMapper(MappingContext<? extends ElasticsearchPersistentEntity<?>, ElasticsearchPersistentProperty> mappingContext) {
        super(new DefaultEntityMapper());
        this.mappingContext = mappingContext;
    }

    public ExtResultMapper(EntityMapper entityMapper) {
        super(entityMapper);
    }

    public ExtResultMapper(
            MappingContext<? extends ElasticsearchPersistentEntity<?>, ElasticsearchPersistentProperty> mappingContext,
            EntityMapper entityMapper) {
        super(entityMapper);
        this.mappingContext = mappingContext;
    }

    @Override
    public <T> AggregatedPage<T> mapResults(SearchResponse response, Class<T> clazz, Pageable pageable) {
        long totalHits = response.getHits().totalHits();
        List<T> results = new ArrayList<>();
        for (SearchHit hit : response.getHits()) {
            if (hit != null) {
                T result = null;
                if (StringUtils.hasText(hit.sourceAsString())) {
                    result = mapEntity(hit.sourceAsString(), clazz);
                } else {
                    result = mapEntity(hit.getFields().values(), clazz);
                }
                setPersistentEntityId(result, hit.getId(), clazz);
                setPersistentEntityVersion(result, hit.getVersion(), clazz);
                populateScriptFields(result, hit);
               
               // 高亮查询
                populateHighLightedFields(result, hit.getHighlightFields());
                results.add(result);
            }
        }

        return new AggregatedPageImpl<T>(results, pageable, totalHits, response.getAggregations(), response.getScrollId());
    }

    private <T>  void populateHighLightedFields(T result, Map<String, HighlightField> highlightFields) {
        for (HighlightField field : highlightFields.values()) {
            try {
                PropertyUtils.setProperty(result, field.getName(), concat(field.fragments()));
            } catch (InvocationTargetException | IllegalAccessException | NoSuchMethodException e) {
                throw new ElasticsearchException("failed to set highlighted value for field: " + field.getName()
                        + " with value: " + Arrays.toString(field.getFragments()), e);
            }
        }
    }

    private String concat(Text[] texts) {
        StringBuffer sb = new StringBuffer();
        for (Text text : texts) {
            sb.append(text.toString());
        }
        return sb.toString();
    }

    private <T> void populateScriptFields(T result, SearchHit hit) {
        if (hit.getFields() != null && !hit.getFields().isEmpty() && result != null) {
            for (java.lang.reflect.Field field : result.getClass().getDeclaredFields()) {
                ScriptedField scriptedField = field.getAnnotation(ScriptedField.class);
                if (scriptedField != null) {
                    String name = scriptedField.name().isEmpty() ? field.getName() : scriptedField.name();
                    SearchHitField searchHitField = hit.getFields().get(name);
                    if (searchHitField != null) {
                        field.setAccessible(true);
                        try {
                            field.set(result, searchHitField.getValue());
                        } catch (IllegalArgumentException e) {
                            throw new ElasticsearchException("failed to set scripted field: " + name + " with value: "
                                    + searchHitField.getValue(), e);
                        } catch (IllegalAccessException e) {
                            throw new ElasticsearchException("failed to access scripted field: " + name, e);
                        }
                    }
                }
            }
        }
    }

    private <T> T mapEntity(Collection<SearchHitField> values, Class<T> clazz) {
        return mapEntity(buildJSONFromFields(values), clazz);
    }

    private String buildJSONFromFields(Collection<SearchHitField> values) {
        JsonFactory nodeFactory = new JsonFactory();
        try {
            ByteArrayOutputStream stream = new ByteArrayOutputStream();
            JsonGenerator generator = nodeFactory.createGenerator(stream, JsonEncoding.UTF8);
            generator.writeStartObject();
            for (SearchHitField value : values) {
                if (value.getValues().size() > 1) {
                    generator.writeArrayFieldStart(value.getName());
                    for (Object val : value.getValues()) {
                        generator.writeObject(val);
                    }
                    generator.writeEndArray();
                } else {
                    generator.writeObjectField(value.getName(), value.getValue());
                }
            }
            generator.writeEndObject();
            generator.flush();
            return new String(stream.toByteArray(), Charset.forName("UTF-8"));
        } catch (IOException e) {
            return null;
        }
    }

    @Override
    public <T> T mapResult(GetResponse response, Class<T> clazz) {
        T result = mapEntity(response.getSourceAsString(), clazz);
        if (result != null) {
            setPersistentEntityId(result, response.getId(), clazz);
            setPersistentEntityVersion(result, response.getVersion(), clazz);
        }
        return result;
    }

    @Override
    public <T> LinkedList<T> mapResults(MultiGetResponse responses, Class<T> clazz) {
        LinkedList<T> list = new LinkedList<>();
        for (MultiGetItemResponse response : responses.getResponses()) {
            if (!response.isFailed() && response.getResponse().isExists()) {
                T result = mapEntity(response.getResponse().getSourceAsString(), clazz);
                setPersistentEntityId(result, response.getResponse().getId(), clazz);
                setPersistentEntityVersion(result, response.getResponse().getVersion(), clazz);
                list.add(result);
            }
        }
        return list;
    }

    private <T> void setPersistentEntityId(T result, String id, Class<T> clazz) {

        if (mappingContext != null && clazz.isAnnotationPresent(Document.class)) {

            ElasticsearchPersistentEntity<?> persistentEntity = mappingContext.getRequiredPersistentEntity(clazz);
            ElasticsearchPersistentProperty idProperty = persistentEntity.getIdProperty();

            // Only deal with String because ES generated Ids are strings !
            if (idProperty != null && idProperty.getType().isAssignableFrom(String.class)) {
                persistentEntity.getPropertyAccessor(result).setProperty(idProperty, id);
            }

        }
    }

    private <T> void setPersistentEntityVersion(T result, long version, Class<T> clazz) {
        if (mappingContext != null && clazz.isAnnotationPresent(Document.class)) {

            ElasticsearchPersistentEntity<?> persistentEntity = mappingContext.getPersistentEntity(clazz);
            ElasticsearchPersistentProperty versionProperty = persistentEntity.getVersionProperty();

            // Only deal with Long because ES versions are longs !
            if (versionProperty != null && versionProperty.getType().isAssignableFrom(Long.class)) {
                // check that a version was actually returned in the response, -1 would indicate that
                // a search didn't request the version ids in the response, which would be an issue
                Assert.isTrue(version != -1, "Version in response is -1");
                persistentEntity.getPropertyAccessor(result).setProperty(versionProperty, version);
            }
        }
    }
}

注意这里使用到了 PropertyUtils ，需要引入一个 Apache 的依赖。

<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.3</version>
</dependency>

自定义 ResultMapper 写好之后，添加 @Component 注解，表示为 Spring 的一个组件，在类中进行注入使用即可。

最后

本文示例项目地址：https://github.com/Mosiki/SpringDataElasticSearchQuickStartExample

有疑问?

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