总结一下elasticsearch java api开发过程中遇到的一些问题。
elasticsearch版本：5.1.2PreBuiltTransportClient找不到
当我们按elasticsearch老版本2.x一样引用maven文件时，如下：在我们创建elasticsearch的TransportClient时候 TransportClient client = new PreBuiltTransportClient（），提示无法找到PreBuiltTransportClient类。 这是由于elasticsearch从5.x开始客户端放在了新的jar包里，我们需要引用如下：org.elasticsearch elasticsearch 5.1.2
找不到log4j类 执行java查询时候，报错如下：org.elasticsearch.client transport 5.1.2
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/logging/log4j/Logger at org.elasticsearch.common.logging.Loggers.getLogger(Loggers.java:105) at org.elasticsearch.common.logging.Loggers.getLogger(Loggers.java:72) at org.elasticsearch.common.component.AbstractComponent.只是由于elasticsearch 5.x中需要log4j的一些依赖，需要添加，在pom.xml中添加如下maven配置：(AbstractComponent.java:37) at org.elasticsearch.plugins.PluginsService. (PluginsService.java:98) at org.elasticsearch.client.transport.TransportClient.newPluginService(TransportClient.java:94) at org.elasticsearch.client.transport.TransportClient.buildTemplate(TransportClient.java:119) at org.elasticsearch.client.transport.TransportClient. (TransportClient.java:247) at org.elasticsearch.transport.client.PreBuiltTransportClient. (PreBuiltTransportClient.java:125) at org.elasticsearch.transport.client.PreBuiltTransportClient. (PreBuiltTransportClient.java:111) at org.elasticsearch.transport.client.PreBuiltTransportClient. (PreBuiltTransportClient.java:101)Caused by: java.lang.ClassNotFoundException: org.apache.logging.log4j.Logger at java.net.URLClassLoader.findClass(URLClassLoader.java:381) at java.lang.ClassLoader.loadClass(ClassLoader.java:424) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331) at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
index级别settings设置错误 按照2.x的方式构造Setting，如下：org.apache.logging.log4j log4j-api 2.7 org.apache.logging.log4j log4j-core 2.7
Settings settings = Settings.builder()
.put("cluster.name", clusterName) .put("cluster.transport.sniff", true) .put("index.refresh_interval", "60s") .build(); 在执行客户端查询时，报错如下：java.lang.IllegalArgumentException: node settings must not contain any index level settings
at org.elasticsearch.common.settings.SettingsModule.<init>(SettingsModule.java:131) at org.elasticsearch.client.transport.TransportClient.buildTemplate(TransportClient.java:133) at org.elasticsearch.client.transport.TransportClient.<init>(TransportClient.java:247) at org.elasticsearch.transport.client.PreBuiltTransportClient.<init>(PreBuiltTransportClient.java:125) at org.elasticsearch.transport.client.PreBuiltTransportClient.<init>(PreBuiltTransportClient.java:111) at org.elasticsearch.transport.client.PreBuiltTransportClient.<init>(PreBuiltTransportClient.java:101) 即5.x不支持索引级别的设置，即5.x不支持index.refresh_interval配置，且名字也变更了，5.x只支持的Settings配置如下：配置 说明
cluster.name 集群name client.transport.sniff 是否支持自动嗅探 client.transport.ignore_cluster_name Set to true to ignore cluster name validation of connected nodes. (since 0.19.4) client.transport.ping_timeout The time to wait for a ping response from a node. Defaults to 5s. client.transport.nodes_sampler_interval How often to sample / ping the nodes listed and connected. Defaults to 5s. 因此，我们配置如下即可：Settings settings = Settings.builder()
.put("cluster.name", clusterName) .put("client.transport.sniff", true) .build(); 如何指定返回的字段field 在elasticsearch 2.x版本中，如果我们想指定查询返回的字段，可以使用fields字段设置，代码如下：String index = xxx;
String type = xxx; // 指定要返回的字段 String[] fields = new String[2]; fields[0] = "field1"; // 字段1名称 fields[1] = "filed2"; // 字段2名称 // 构造query SearchRequestBuilder requestBuilder = client.prepareSearch(index); requestBuilder .setFrom(0).setSize(100) .setTimeout(TimeValue.timeValueMillis(300)) .setTypes(type) .addFields(fields); // bool 条件 BoolQueryBuilder boolQueryBuilder = QueryBuilders.boolQuery(); TermQueryBuilder tqb = QueryBuilders.termQuery("field1", "val1"); boolQueryBuilder.must(tqb); // set query requestBuilder.setQuery(boolQueryBuilder); // get response SearchResponse response = requestBuilder.execute().actionGet(); // 遍历返回的字段 SearchHits searchHits = response.getHits(); for (SearchHit hit : searchHits) { System.out.println(hit.getFields().get("filed1").getValue().toString()); } 但是在5.x中，setFileds函数已经不存在了，那在5.x中通过什么来指定返回的字段呢，答案是Source字段，通过setFetchSource函数来指定要返回的字段，可以指定单个filed或者一个filed数组，通过getSource来获取返回的字段值，其中setFetchSource有三个版本，说明如下： 1. setFetchSource(boolean fetch) 用于指定是否返回字段，默认为true，如果为false，则getSource返回null。 2. setFetchSource(String include, String exclude) 用于指定包含的一个字段和排除的一个字段，实际会返回include字段及其对应的值。 3. setFetchSource(String[] includes, String[] excludes) 用于指定包含的多个字段和排除的多个字段。 下面以具体代码来说明如何获取：String index = xxx;
String type = xxx; // 指定要返回的字段 String[] fields = new String[2]; fields[0] = "field1"; // 字段1名称 fields[1] = "filed2"; // 字段2名称 // 构造query SearchRequestBuilder requestBuilder = client.prepareSearch(index); requestBuilder .setFrom(0).setSize(100) .setTimeout(TimeValue.timeValueMillis(300)) .setTypes(type) // 指定返回的字段，排除字段设为null .setFetchSource(fields, null); // bool 条件 BoolQueryBuilder boolQueryBuilder = QueryBuilders.boolQuery(); TermQueryBuilder tqb = QueryBuilders.termQuery("field1", "val1"); boolQueryBuilder.must(tqb); // set query requestBuilder.setQuery(boolQueryBuilder); // get response SearchResponse response = requestBuilder.execute().actionGet(); // 遍历返回的字段 SearchHits searchHits = response.getHits(); for (SearchHit hit : searchHits) { // 注意这里和2.x不同的是使用getSource函数 System.out.println(hit.getSource().get("filed1")); } --------------------- 作者：简牧 来源：CSDN 原文：https://blog.csdn.net/qq_35799003/article/details/70210919 版权声明：本文为博主原创文章，转载请附上博文链接！