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

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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:

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@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

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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。

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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。

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<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?

欢迎来信,给我写信