如何在 Spring Boot 项目中实现对 Elasticsearch 的集成？

在 Spring Boot 项目中集成 Elasticsearch 可以借助 Spring Data Elasticsearch 来实现，下面为你详细介绍具体步骤和示例代码。

1. 添加依赖

在 pom.xml 中添加 Spring Data Elasticsearch 依赖，若使用 Maven，添加如下内容：

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-elasticsearch</artifactId>
    </dependency>
</dependencies>

2. 配置 Elasticsearch 连接

在 application.properties 或者 application.yml 中配置 Elasticsearch 的连接信息。以 application.properties 为例：

spring.elasticsearch.uris=http://localhost:9200

3. 创建实体类

创建 Java 类来映射 Elasticsearch 中的文档。

import org.springframework.data.annotation.Id;
import org.springframework.data.elasticsearch.annotations.Document;
import org.springframework.data.elasticsearch.annotations.Field;
import org.springframework.data.elasticsearch.annotations.FieldType;

@Document(indexName = "products")
public class Product {
    @Id
    private String id;
    @Field(type = FieldType.Text)
    private String name;
    @Field(type = FieldType.Double)
    private double price;

    public Product() {
    }

    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Product{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", price=" + price +
                '}';
    }
}

4. 创建 Repository 接口

创建继承自 ElasticsearchRepository 的接口，用于执行数据库操作。

import org.springframework.data.elasticsearch.repository.ElasticsearchRepository;

public interface ProductRepository extends ElasticsearchRepository<Product, String> {
}

5. 使用 Repository 进行操作

在服务类或者控制器中使用 ProductRepository 进行数据库操作。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class ProductService {
    @Autowired
    private ProductRepository productRepository;

    public Product saveProduct(Product product) {
        return productRepository.save(product);
    }

    public List<Product> getAllProducts() {
        return productRepository.findAll();
    }

    public Product getProductById(String id) {
        return productRepository.findById(id).orElse(null);
    }

    public void deleteProduct(String id) {
        productRepository.deleteById(id);
    }
}

6. 控制器示例

创建一个控制器来测试这些操作。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/products")
public class ProductController {
    @Autowired
    private ProductService productService;

    @PostMapping
    public Product saveProduct(@RequestBody Product product) {
        return productService.saveProduct(product);
    }

    @GetMapping
    public List<Product> getAllProducts() {
        return productService.getAllProducts();
    }

    @GetMapping("/{id}")
    public Product getProductById(@PathVariable String id) {
        return productService.getProductById(id);
    }

    @DeleteMapping("/{id}")
    public void deleteProduct(@PathVariable String id) {
        productService.deleteProduct(id);
    }
}

总结

通过以上步骤，你就能够在 Spring Boot 项目中集成 Elasticsearch，并实现基本的增删查操作。若有更复杂的查询需求，可以在 ProductRepository 中自定义查询方法。

以下是完整的代码示例，包含实体类、Repository 接口、服务类和控制器类：

Product.java

import org.springframework.data.annotation.Id;
import org.springframework.data.elasticsearch.annotations.Document;
import org.springframework.data.elasticsearch.annotations.Field;
import org.springframework.data.elasticsearch.annotations.FieldType;

@Document(indexName = "products")
public class Product {
    @Id
    private String id;
    @Field(type = FieldType.Text)
    private String name;
    @Field(type = FieldType.Double)
    private double price;

    public Product() {
    }

    public Product(String name, double price) {
        this.name = name;
        this.price = price;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    @Override
    public String toString() {
        return "Product{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", price=" + price +
                '}';
    }
}    

ProductController.java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/products")
public class ProductController {
    @Autowired
    private ProductService productService;

    @PostMapping
    public Product saveProduct(@RequestBody Product product) {
        return productService.saveProduct(product);
    }

    @GetMapping
    public List<Product> getAllProducts() {
        return productService.getAllProducts();
    }

    @GetMapping("/{id}")
    public Product getProductById(@PathVariable String id) {
        return productService.getProductById(id);
    }

    @DeleteMapping("/{id}")
    public void deleteProduct(@PathVariable String id) {
        productService.deleteProduct(id);
    }
}    

ProductRepository.java

import org.springframework.data.elasticsearch.repository.ElasticsearchRepository;

public interface ProductRepository extends ElasticsearchRepository<Product, String> {
}    

ProductService.java

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class ProductService {
    @Autowired
    private ProductRepository productRepository;

    public Product saveProduct(Product product) {
        return productRepository.save(product);
    }

    public List<Product> getAllProducts() {
        return productRepository.findAll();
    }

    public Product getProductById(String id) {
        return productRepository.findById(id).orElse(null);
    }

    public void deleteProduct(String id) {
        productRepository.deleteById(id);
    }
}