Guwan
/
JPA-Test
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

cs

This commit is contained in:
Guwan 2025-04-17 22:38:25 +08:00
commit af03293df7
13 changed files with 1121 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
.gitignore vendored Normal file
View File

@ -0,0 +1,52 @@
# Compiled class file
*.class
# Eclipse
.project
.classpath
.settings/
# Intellij
*.ipr
*.iml
*.iws
.idea/
# Maven
target/
# Gradle
build
.gradle
# Log file
*.log
# out
**/out/
# BlueJ files
*.ctxt
# Mobile Tools for Java (J2ME)
.mtj.tmp/
# Package Files #
*.jar
*.war
*.nar
*.ear
*.zip
*.tar
*.tar.gz
*.rar
*.pid
*.orig
# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
hs_err_pid*
# Mac
.DS_Store
*.tmp

69
pom.xml Normal file
View File

@ -0,0 +1,69 @@
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>3.2.0</version>
<relativePath/>
</parent>
<groupId>com.guwan.backend</groupId>
<artifactId>jpa-test</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>jpa-test</name>
<description>Custom JPA Join Query Demo</description>
<properties>
<java.version>17</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-jdbc</artifactId>
</dependency>
<dependency>
<groupId>com.mysql</groupId>
<artifactId>mysql-connector-j</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
<configuration>
<excludes>
<exclude>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</exclude>
</excludes>
</configuration>
</plugin>
</plugins>
</build>
</project>

14
src/main/java/com/guwan/backend/JpaTestApplication.java Normal file
View File

@ -0,0 +1,14 @@
package com.guwan.backend;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
@SpringBootApplication
@EnableJpaRepositories
public class JpaTestApplication {
public static void main(String[] args) {
SpringApplication.run(JpaTestApplication.class, args);
}
}

570
src/main/java/com/guwan/backend/MergeStrategy/JoinBuilder.java Normal file
View File

@ -0,0 +1,570 @@
package com.guwan.backend.MergeStrategy;
import jakarta.persistence.EntityManager;
import jakarta.persistence.criteria.*;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.data.jpa.repository.query.QueryUtils;
import java.lang.reflect.Constructor;
import java.util.*;
import java.util.function.Function;
import java.util.stream.Collectors;
/**
* 自定义连表查询构建器
* 用于构建复杂的多表连接查询，支持指定返回字段和条件
*/
public class JoinBuilder<T> {
private final Class<T> rootClass;
private final Map<Class<?>, JoinInfo> joins = new HashMap<>();
private final Map<Class<?>, List<Condition>> conditions = new HashMap<>();
private Map<Class<?>, String[]> selectedFields;
private Map<String, Object> namedSelections = new LinkedHashMap<>();
private JoinBuilder(Class<T> rootClass) {
this.rootClass = rootClass;
}
public static <T> JoinBuilder<T> from(Class<T> rootClass) {
return new JoinBuilder<>(rootClass);
}
/**
* 添加连接表
* @param joinClass 要连接的表实体类
* @param sourceField 主表的外键字段
* @param targetField 连接表的目标字段
*/
public JoinBuilder<T> join(Class<?> joinClass, String sourceField, String targetField) {
joins.put(joinClass, new JoinInfo(sourceField, targetField));
return this;
}
/**
* 添加连接表（使用方法引用）
* @param joinClass 要连接的表实体类
* @param sourceFieldGetter 主表外键字段的getter方法引用
* @param targetFieldGetter 连接表目标字段的getter方法引用
*/
public <J, V> JoinBuilder<T> join(Class<J> joinClass,
Function<T, V> sourceFieldGetter,
Function<J, V> targetFieldGetter) {
String sourceField = getFieldNameFromGetter(sourceFieldGetter);
String targetField = getFieldNameFromGetter(targetFieldGetter);
return join(joinClass, sourceField, targetField);
}
/**
* 添加等值条件
* @param entityClass 实体类
* @param fieldName 字段名
* @param value 字段值
*/
public <V> JoinBuilder<T> equal(Class<?> entityClass, String fieldName, V value) {
if (!conditions.containsKey(entityClass)) {
conditions.put(entityClass, new ArrayList<>());
}
conditions.get(entityClass).add(new Condition(fieldName, value, Operator.EQUAL));
return this;
}
/**
* 添加等值条件（使用方法引用）
* @param entityClass 实体类
* @param fieldGetter 字段的getter方法引用
* @param value 字段值
*/
public <E, V> JoinBuilder<T> equal(Class<E> entityClass, Function<E, V> fieldGetter, V value) {
String fieldName = getFieldNameFromGetter(fieldGetter);
return equal(entityClass, fieldName, value);
}
/**
* 选择返回的字段
* @param selectedFields 每个实体类需要返回的字段映射
*/
public JoinBuilder<T> selectFields(Map<Class<?>, String[]> selectedFields) {
this.selectedFields = selectedFields;
return this;
}
/**
* 选择返回的字段（使用方法引用）
* @param fieldGetters 方法引用列表
*/
@SafeVarargs
public final <E> JoinBuilder<T> select(Class<E> entityClass, Function<E, ?>... fieldGetters) {
if (selectedFields == null) {
selectedFields = new HashMap<>();
}
String[] fieldNames = Arrays.stream(fieldGetters)
.map(this::getFieldNameFromGetter)
.toArray(String[]::new);
selectedFields.put(entityClass, fieldNames);
return this;
}
/**
* 添加一个具有别名的字段选择（优先级高于select方法）
* @param alias 字段别名
* @param entityClass 实体类
* @param fieldGetter 字段的getter方法引用
*/
public <E, V> JoinBuilder<T> selectAs(String alias, Class<E> entityClass, Function<E, V> fieldGetter) {
String fieldName = getFieldNameFromGetter(fieldGetter);
// 存储字段信息，稍后在configureSelections处理
if (selectedFields == null) {
selectedFields = new HashMap<>();
}
if (!selectedFields.containsKey(entityClass)) {
selectedFields.put(entityClass, new String[0]);
}
namedSelections.put(alias, new SelectionInfo(entityClass, fieldName));
return this;
}
/**
* 添加一个具有别名的字段选择（字符串版本）
* @param alias 字段别名
* @param entityClass 实体类
* @param fieldName 字段名称
*/
public <E> JoinBuilder<T> selectAs(String alias, Class<E> entityClass, String fieldName) {
// 存储字段信息，稍后在configureSelections处理
if (selectedFields == null) {
selectedFields = new HashMap<>();
}
if (!selectedFields.containsKey(entityClass)) {
selectedFields.put(entityClass, new String[0]);
}
namedSelections.put(alias, new SelectionInfo(entityClass, fieldName));
return this;
}
/**
* 设置实体间字段映射关系的别名，以便对应DTO字段
* @param dtoClass DTO类
* @param mappings 字段映射
*/
@SafeVarargs
public final <R> JoinBuilder<T> selectDto(Class<R> dtoClass, FieldMapping<R, ?>... mappings) {
for (FieldMapping<R, ?> mapping : mappings) {
String dtoFieldName = getFieldNameFromGetter(mapping.getDtoFieldGetter());
String entityFieldName = getFieldNameFromGetter(mapping.getEntityFieldGetter());
Class<?> entityClass = mapping.getEntityClass();
// 存储字段信息，稍后在configureSelections处理
if (selectedFields == null) {
selectedFields = new HashMap<>();
}
if (!selectedFields.containsKey(entityClass)) {
selectedFields.put(entityClass, new String[0]);
}
namedSelections.put(dtoFieldName, new SelectionInfo(entityClass, entityFieldName));
}
return this;
}
/**
* 构建规范查询
* @return Specification<T> 查询规范
*/
public Specification<T> build() {
return (root, query, criteriaBuilder) -> {
// 创建连接关系
Map<Class<?>, From<?, ?>> joinMap = createJoins(root, query);
// 应用连表条件和其他条件
List<Predicate> predicates = applyAllConditions(root, joinMap, criteriaBuilder);
// 设置查询结果投影
configureSelections(root, joinMap, query);
return criteriaBuilder.and(predicates.toArray(new Predicate[0]));
};
}
/**
* 执行查询并返回结果
* @param entityManager EntityManager实例
* @return 查询结果列表
*/
public List<Object[]> execute(EntityManager entityManager) {
// 创建CriteriaBuilder
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
// 创建CriteriaQuery
CriteriaQuery<Object[]> criteriaQuery = criteriaBuilder.createQuery(Object[].class);
// 设置根实体
Root<T> root = criteriaQuery.from(rootClass);
// 创建连接关系
Map<Class<?>, From<?, ?>> fromMap = createJoins(root, criteriaQuery);
// 应用所有条件，包括表之间的连接条件和额外查询条件
List<Predicate> predicates = applyAllConditions(root, fromMap, criteriaBuilder);
// 添加条件到查询
if (!predicates.isEmpty()) {
criteriaQuery.where(criteriaBuilder.and(predicates.toArray(new Predicate[0])));
}
// 设置查询结果投影
configureSelections(root, fromMap, criteriaQuery);
// 执行查询并返回结果
return entityManager.createQuery(criteriaQuery).getResultList();
}
/**
* 创建连接 - 修改为使用from而不是join
*/
private Map<Class<?>, From<?, ?>> createJoins(Root<T> root, CriteriaQuery<?> query) {
Map<Class<?>, From<?, ?>> fromMap = new HashMap<>();
fromMap.put(rootClass, root);
// 对于每个需要连接的表，创建一个单独的From
for (Map.Entry<Class<?>, JoinInfo> entry : joins.entrySet()) {
Class<?> joinClass = entry.getKey();
From<?, ?> joinRoot = query.from(joinClass);
fromMap.put(joinClass, joinRoot);
}
return fromMap;
}
/**
* 应用所有条件，包括表之间的连接条件和额外查询条件
*/
private List<Predicate> applyAllConditions(Root<T> root, Map<Class<?>, From<?, ?>> fromMap, CriteriaBuilder criteriaBuilder) {
List<Predicate> predicates = new ArrayList<>();
// 首先添加表连接条件
for (Map.Entry<Class<?>, JoinInfo> entry : joins.entrySet()) {
Class<?> joinClass = entry.getKey();
JoinInfo joinInfo = entry.getValue();
if (fromMap.containsKey(joinClass)) {
From<?, ?> joinFrom = fromMap.get(joinClass);
Predicate joinCondition = criteriaBuilder.equal(
root.get(joinInfo.sourceField),
joinFrom.get(joinInfo.targetField)
);
predicates.add(joinCondition);
}
}
// 然后添加普通查询条件
for (Class<?> entityClass : conditions.keySet()) {
for (Condition condition : conditions.get(entityClass)) {
if (fromMap.containsKey(entityClass)) {
From<?, ?> from = fromMap.get(entityClass);
predicates.add(applyCondition(condition, from, criteriaBuilder));
}
}
}
return predicates;
}
/**
* 执行查询并直接映射到DTO对象
* @param entityManager EntityManager实例
* @param dtoClass DTO类
* @param <R> DTO类型
* @return DTO对象列表
*/
public <R> List<R> executeAndMap(EntityManager entityManager, Class<R> dtoClass) {
List<Object[]> results = execute(entityManager);
return mapToDto(results, dtoClass);
}
/**
* 将查询结果映射到DTO对象
* @param results 查询结果
* @param dtoClass DTO类
* @param <R> DTO类型
* @return DTO对象列表
*/
public <R> List<R> mapToDto(List<Object[]> results, Class<R> dtoClass) {
try {
// 获取所有字段名（顺序与查询结果一致）
List<String> fieldNames = new ArrayList<>(namedSelections.keySet());
// 获取构造函数
Class<?>[] paramTypes = new Class[fieldNames.size()];
Arrays.fill(paramTypes, Object.class);
Constructor<R> constructor = dtoClass.getDeclaredConstructor(paramTypes);
// 映射结果
return results.stream()
.map(row -> {
try {
return constructor.newInstance(row);
} catch (Exception e) {
throw new RuntimeException("Failed to map result to DTO: " + e.getMessage(), e);
}
})
.collect(Collectors.toList());
} catch (Exception e) {
throw new RuntimeException("Failed to create DTO mapper: " + e.getMessage(), e);
}
}
/**
* 配置查询结果投影
*/
private void configureSelections(Root<T> root, Map<Class<?>, From<?, ?>> fromMap, CriteriaQuery<?> query) {
if (!namedSelections.isEmpty()) {
// 处理命名选择
List<Selection<?>> selections = new ArrayList<>();
for (Map.Entry<String, Object> entry : namedSelections.entrySet()) {
String alias = entry.getKey();
Object value = entry.getValue();
if (value instanceof SelectionInfo) {
SelectionInfo info = (SelectionInfo) value;
Path<?> path;
if (fromMap.containsKey(info.entityClass)) {
path = fromMap.get(info.entityClass).get(info.fieldName);
selections.add(path.alias(alias));
}
}
}
if (!selections.isEmpty()) {
query.multiselect(selections);
return;
}
}
// 如果没有命名选择或处理失败，回退到原来的处理方式
if (selectedFields != null && !selectedFields.isEmpty()) {
List<Selection<?>> selections = new ArrayList<>();
// 添加根实体的选择字段
if (selectedFields.containsKey(rootClass)) {
for (String field : selectedFields.get(rootClass)) {
selections.add(root.get(field));
}
}
// 添加关联实体的选择字段
for (Class<?> entityClass : selectedFields.keySet()) {
if (entityClass != rootClass && fromMap.containsKey(entityClass)) {
From<?, ?> from = fromMap.get(entityClass);
for (String field : selectedFields.get(entityClass)) {
selections.add(from.get(field));
}
}
}
if (!selections.isEmpty()) {
query.multiselect(selections);
}
}
}
private <X> Predicate applyCondition(Condition condition, From<?, X> from, CriteriaBuilder criteriaBuilder) {
switch (condition.operator) {
case EQUAL:
return criteriaBuilder.equal(from.get(condition.fieldName), condition.value);
// 可以添加更多操作符支持，如LIKE, IN, GREATER_THAN等
default:
throw new UnsupportedOperationException("Unsupported operator: " + condition.operator);
}
}
/**
* 从getter方法引用中提取属性名
*/
private <E, R> String getFieldNameFromGetter(Function<E, R> getter) {
// 直接尝试从方法引用的toString中获取
try {
String methodRef = getter.toString();
if (methodRef.contains("::")) {
// 处理方法引用格式: com.example.Entity::getName
String methodName = methodRef.substring(methodRef.lastIndexOf("::") + 2);
return extractFieldNameFromMethod(methodName);
} else if (methodRef.contains("->")) {
// 处理Lambda表达式格式: (Entity e) -> e.getName()
String methodCall = methodRef.substring(methodRef.indexOf("->") + 2).trim();
String methodName = methodCall.substring(methodCall.lastIndexOf(".") + 1);
if (methodName.endsWith(")")) {
methodName = methodName.substring(0, methodName.indexOf("("));
}
return extractFieldNameFromMethod(methodName);
}
} catch (Exception ignored) {
// 忽略异常，尝试下一种方法
}
try {
String getterName = getter.getClass().getName();
if (getterName.contains("$$Lambda$")) {
// 处理Lambda表达式
if (getterName.contains("get")) {
// 尝试从名称中提取字段名
int getIndex = getterName.lastIndexOf("get");
if (getIndex >= 0 && getIndex + 3 < getterName.length()) {
String fieldName = getterName.substring(getIndex + 3);
if (fieldName.indexOf('$') > 0) {
fieldName = fieldName.substring(0, fieldName.indexOf('$'));
}
return fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);
}
}
}
} catch (Exception ignored) {
// 忽略异常，fallback到基于字符串的方法
}
// Fallback到基于字符串的方法
String methodReference = getter.toString();
return getFieldNameFromGetterString(methodReference);
}
/**
* 从getter方法字符串中提取属性名
*/
private String getFieldNameFromGetterString(String methodReference) {
// 方法引用的格式通常是：类名::get字段名 或 Lambda表达式
if (methodReference.contains("::")) {
// 处理方法引用格式: com.example.Entity::getName
String methodName = methodReference.substring(methodReference.lastIndexOf("::") + 2);
return extractFieldNameFromMethod(methodName);
} else if (methodReference.contains("->")) {
// 处理Lambda表达式格式: (Entity e) -> e.getName()
String methodCall = methodReference.substring(methodReference.indexOf("->") + 2).trim();
String methodName = methodCall.substring(methodCall.lastIndexOf(".") + 1);
if (methodName.endsWith(")")) {
methodName = methodName.substring(0, methodName.indexOf("("));
}
return extractFieldNameFromMethod(methodName);
}
// 无法识别的格式，返回原始字符串
return methodReference;
}
/**
* 从方法名中提取字段名
*/
private String extractFieldNameFromMethod(String methodName) {
if (methodName.startsWith("get") && methodName.length() > 3) {
// getName -> name (首字母小写)
String fieldName = methodName.substring(3);
return fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);
} else if (methodName.startsWith("is") && methodName.length() > 2) {
// isActive -> active (首字母小写)
String fieldName = methodName.substring(2);
return fieldName.substring(0, 1).toLowerCase() + fieldName.substring(1);
}
return methodName;
}
/**
* 首字母大写
*/
private String capitalize(String str) {
if (str == null || str.isEmpty()) {
return str;
}
return str.substring(0, 1).toUpperCase() + str.substring(1);
}
private enum Operator {
EQUAL
// 可以添加更多操作符支持，如LIKE, IN, GREATER_THAN等
}
private static class Condition {
private final String fieldName;
private final Object value;
private final Operator operator;
Condition(String fieldName, Object value, Operator operator) {
this.fieldName = fieldName;
this.value = value;
this.operator = operator;
}
}
/**
* 连接信息
*/
private static class JoinInfo {
private final String sourceField;
private final String targetField;
JoinInfo(String sourceField, String targetField) {
this.sourceField = sourceField;
this.targetField = targetField;
}
}
/**
* 选择字段信息
*/
private static class SelectionInfo {
private final Class<?> entityClass;
private final String fieldName;
SelectionInfo(Class<?> entityClass, String fieldName) {
this.entityClass = entityClass;
this.fieldName = fieldName;
}
}
/**
* 字段映射定义，用于DTO映射
*/
public static class FieldMapping<D, E> {
private final Function<D, ?> dtoFieldGetter;
private final Function<E, ?> entityFieldGetter;
private final Class<E> entityClass;
private FieldMapping(Function<D, ?> dtoFieldGetter, Function<E, ?> entityFieldGetter, Class<E> entityClass) {
this.dtoFieldGetter = dtoFieldGetter;
this.entityFieldGetter = entityFieldGetter;
this.entityClass = entityClass;
}
public static <D, E, V> FieldMapping<D, E> of(Function<D, V> dtoFieldGetter, Function<E, V> entityFieldGetter) {
// 通过反射或其他方式获取entityClass
Class<E> entityClass = null;
try {
// 尝试从方法引用中提取类信息
String methodRef = entityFieldGetter.toString();
if (methodRef.contains("::")) {
String className = methodRef.substring(0, methodRef.indexOf("::"));
entityClass = (Class<E>) Class.forName(className);
}
} catch (Exception e) {
// 忽略异常，entityClass将在运行时确定
}
return new FieldMapping<>(dtoFieldGetter, entityFieldGetter, entityClass);
}
public Function<D, ?> getDtoFieldGetter() {
return dtoFieldGetter;
}
public Function<E, ?> getEntityFieldGetter() {
return entityFieldGetter;
}
public Class<?> getEntityClass() {
return entityClass;
}
}
}

22
src/main/java/com/guwan/backend/jpaTest/Department.java Normal file
View File

@ -0,0 +1,22 @@
package com.guwan.backend.jpaTest;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Table;
import lombok.Data;
import lombok.NoArgsConstructor;
@Entity
@Table(name = "departments")
@Data
@NoArgsConstructor
public class Department {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
}

29
src/main/java/com/guwan/backend/jpaTest/Employee.java Normal file
View File

@ -0,0 +1,29 @@
package com.guwan.backend.jpaTest;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Column;
import jakarta.persistence.Table;
import lombok.Data;
import lombok.NoArgsConstructor;
@Entity
@Table(name = "employees")
@Data
@NoArgsConstructor
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
@Column(name = "department_id")
private Long departmentId;
@Column(name = "project_id")
private Long projectId;
}

57
src/main/java/com/guwan/backend/jpaTest/EmployeeController.java Normal file
View File

@ -0,0 +1,57 @@
package com.guwan.backend.jpaTest;
import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import java.sql.ResultSet;
import java.util.List;
@RestController
@RequestMapping("/api/employees")
public class EmployeeController {
@Autowired
private EmployeeService employeeService;
@Autowired
private JdbcTemplate jdbcTemplate;
@PersistenceContext
private EntityManager entityManager;
/**
* 获取员工详细信息，包含部门和项目信息
* 使用Spring JdbcTemplate直接映射SQL结果
*
* @param departmentName 部门名称过滤条件
* @param projectDeleted 项目是否已删除的过滤条件
* @return 员工DTO列表
*/
@GetMapping("/details")
public List<EmployeeDTO> getEmployeeDetails(
@RequestParam(required = false) String departmentName,
@RequestParam(required = false, defaultValue = "false") boolean projectDeleted) {
return employeeService.getEmployeeDetails(departmentName, projectDeleted);
}
/**
* 根据条件查询员工信息
*
* @param employeeName 员工名称过滤条件，可选
* @param departmentName 部门名称过滤条件，可选
* @return 员工DTO列表
*/
@GetMapping("/search")
public List<EmployeeDTO> searchEmployees(
@RequestParam(required = false) String employeeName,
@RequestParam(required = false) String departmentName) {
return employeeService.findEmployees(employeeName, departmentName);
}
}

29
src/main/java/com/guwan/backend/jpaTest/EmployeeDTO.java Normal file
View File

@ -0,0 +1,29 @@
package com.guwan.backend.jpaTest;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class EmployeeDTO {
private Long employeeId;
private String employeeName;
private String departmentName;
private String projectName;
/**
* 用于JoinBuilder映射的构造函数
* @param employeeId 员工ID
* @param employeeName 员工姓名
* @param departmentName 部门名称
* @param projectName 项目名称
*/
public EmployeeDTO(Object employeeId, Object employeeName, Object departmentName, Object projectName) {
this.employeeId = employeeId != null ? Long.valueOf(employeeId.toString()) : null;
this.employeeName = employeeName != null ? employeeName.toString() : null;
this.departmentName = departmentName != null ? departmentName.toString() : null;
this.projectName = projectName != null ? projectName.toString() : null;
}
}

10
src/main/java/com/guwan/backend/jpaTest/EmployeeRepository.java Normal file
View File

@ -0,0 +1,10 @@
package com.guwan.backend.jpaTest;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.stereotype.Repository;
@Repository
public interface EmployeeRepository extends JpaRepository<Employee, Long>, JpaSpecificationExecutor<Employee> {
// 自定义查询方法可以在这里添加
}

87
src/main/java/com/guwan/backend/jpaTest/EmployeeService.java Normal file
View File

@ -0,0 +1,87 @@
package com.guwan.backend.jpaTest;
import com.guwan.backend.MergeStrategy.JoinBuilder;
import com.guwan.backend.MergeStrategy.JoinBuilder.FieldMapping;
import jakarta.persistence.EntityManager;
import jakarta.persistence.PersistenceContext;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
@Service
public class EmployeeService {
@Autowired
private EmployeeRepository employeeRepository;
@PersistenceContext
private EntityManager entityManager;
/**
* 获取员工详细信息，包含部门和项目信息
* 使用字符串方式指定字段，并直接映射到DTO
*
* @param departmentName 部门名称过滤条件
* @param projectDeleted 项目是否已删除的过滤条件
* @return 员工DTO列表
*/
public List<EmployeeDTO> getEmployeeDetails(String departmentName, boolean projectDeleted) {
// 创建查询构建器，从Employee实体开始
JoinBuilder<Employee> builder = JoinBuilder.from(Employee.class);
// 添加关联，使用字符串指定实体间的关系字段
builder.join(Department.class, "departmentId", "id");
builder.join(Project.class, "projectId", "id");
// 添加查询条件，使用字符串指定字段
if (departmentName != null && !departmentName.isEmpty()) {
builder.equal(Department.class, "name", departmentName);
}
builder.equal(Project.class, "deleted", projectDeleted);
// 使用selectAs设置字段别名，避免使用FieldMapping
builder.selectAs("employeeId", Employee.class, "id");
builder.selectAs("employeeName", Employee.class, "name");
builder.selectAs("departmentName", Department.class, "name");
builder.selectAs("projectName", Project.class, "name");
// 直接执行查询并映射到DTO
return builder.executeAndMap(entityManager, EmployeeDTO.class);
}
/**
* 使用自定义条件查询员工信息
* 使用selectAs来指定字段别名对应DTO构造函数参数
*
* @param employeeName 员工名称过滤条件，可选
* @param departmentName 部门名称过滤条件，可选
* @return 员工DTO列表
*/
public List<EmployeeDTO> findEmployees(String employeeName, String departmentName) {
JoinBuilder<Employee> builder = JoinBuilder.from(Employee.class);
// 添加关联，使用字符串
builder.join(Department.class, "departmentId", "id");
builder.join(Project.class, "projectId", "id");
// 添加查询条件，使用字符串
if (employeeName != null && !employeeName.isEmpty()) {
builder.equal(Employee.class, "name", employeeName);
}
if (departmentName != null && !departmentName.isEmpty()) {
builder.equal(Department.class, "name", departmentName);
}
// 方式2：使用selectAs直接指定字段别名
builder.selectAs("employeeId", Employee.class, "id");
builder.selectAs("employeeName", Employee.class, "name");
builder.selectAs("departmentName", Department.class, "name");
builder.selectAs("projectName", Project.class, "name");
// 直接执行查询并映射到DTO
return builder.executeAndMap(entityManager, EmployeeDTO.class);
}
}

24
src/main/java/com/guwan/backend/jpaTest/Project.java Normal file
View File

@ -0,0 +1,24 @@
package com.guwan.backend.jpaTest;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Table;
import lombok.Data;
import lombok.NoArgsConstructor;
@Entity
@Table(name = "projects")
@Data
@NoArgsConstructor
public class Project {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
private Boolean deleted = false;
}

140
src/main/java/com/guwan/backend/jpaTest/mapper/QueryResultMapper.java Normal file
View File

@ -0,0 +1,140 @@
package com.guwan.backend.jpaTest.mapper;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
import java.util.stream.Collectors;
/**
* 查询结果映射工具类
* 用于将原始查询结果转换为更有意义的对象
*/
public class QueryResultMapper {
/**
* 将Object[]结果列表映射为指定类型的对象列表
* @param results 查询结果
* @param mapper 映射函数
* @return 映射后的对象列表
*/
public static <T> List<T> mapToList(List<Object[]> results, Function<ResultRow, T> mapper) {
return results.stream()
.map(row -> mapper.apply(new ResultRow(row)))
.collect(Collectors.toList());
}
/**
* 将Object[]结果列表使用命名方式映射为指定类型的对象列表
* @param results 查询结果
* @param columnMap 列名到索引的映射
* @param mapper 映射函数
* @return 映射后的对象列表
*/
public static <T> List<T> mapToListWithNames(List<Object[]> results,
Map<String, Integer> columnMap,
Function<NamedResultRow, T> mapper) {
return results.stream()
.map(row -> mapper.apply(new NamedResultRow(row, columnMap)))
.collect(Collectors.toList());
}
/**
* 结果行封装，提供类型安全的访问方法
*/
public static class ResultRow {
private final Object[] row;
public ResultRow(Object[] row) {
this.row = row;
}
public Long getLong(int index) {
Object value = getValue(index);
if (value == null) return null;
if (value instanceof Long) return (Long) value;
if (value instanceof Number) return ((Number) value).longValue();
return Long.valueOf(value.toString());
}
public Integer getInteger(int index) {
Object value = getValue(index);
if (value == null) return null;
if (value instanceof Integer) return (Integer) value;
if (value instanceof Number) return ((Number) value).intValue();
return Integer.valueOf(value.toString());
}
public String getString(int index) {
Object value = getValue(index);
return value == null ? null : value.toString();
}
public Boolean getBoolean(int index) {
Object value = getValue(index);
if (value == null) return null;
if (value instanceof Boolean) return (Boolean) value;
if (value instanceof Number) return ((Number) value).intValue() != 0;
return Boolean.valueOf(value.toString());
}
public Object getValue(int index) {
if (index < 0 || index >= row.length) {
throw new IndexOutOfBoundsException("索引超出范围: " + index);
}
return row[index];
}
}
/**
* 命名结果行封装，通过列名访问数据
*/
public static class NamedResultRow {
private final Object[] row;
private final Map<String, Integer> columnMap;
public NamedResultRow(Object[] row, Map<String, Integer> columnMap) {
this.row = row;
this.columnMap = columnMap;
}
public Long getLong(String columnName) {
Object value = getValue(columnName);
if (value == null) return null;
if (value instanceof Long) return (Long) value;
if (value instanceof Number) return ((Number) value).longValue();
return Long.valueOf(value.toString());
}
public Integer getInteger(String columnName) {
Object value = getValue(columnName);
if (value == null) return null;
if (value instanceof Integer) return (Integer) value;
if (value instanceof Number) return ((Number) value).intValue();
return Integer.valueOf(value.toString());
}
public String getString(String columnName) {
Object value = getValue(columnName);
return value == null ? null : value.toString();
}
public Boolean getBoolean(String columnName) {
Object value = getValue(columnName);
if (value == null) return null;
if (value instanceof Boolean) return (Boolean) value;
if (value instanceof Number) return ((Number) value).intValue() != 0;
return Boolean.valueOf(value.toString());
}
public Object getValue(String columnName) {
Integer index = columnMap.get(columnName);
if (index == null) {
throw new IllegalArgumentException("列名不存在: " + columnName);
}
if (index < 0 || index >= row.length) {
throw new IndexOutOfBoundsException("索引超出范围: " + index);
}
return row[index];
}
}
}

18
src/main/resources/application.properties Normal file
View File

@ -0,0 +1,18 @@
# MySQL数据库配置
spring.datasource.url=jdbc:mysql://localhost:3306/jpatest?useSSL=false&serverTimezone=UTC&allowPublicKeyRetrieval=true
spring.datasource.driverClassName=com.mysql.cj.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=123456
spring.jpa.database-platform=org.hibernate.dialect.MySQLDialect
# JPA配置
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true
# 服务器配置
server.port=8080
# 日志级别
logging.level.org.hibernate.SQL=DEBUG
logging.level.org.hibernate.type.descriptor.sql.BasicBinder=TRACE