Google Guava集合在实体类中的应用示例

时间：2022-01-10 20:45:43
将实体list，转换成map，拿到所有id的集合方法。减少访问数据库。

 

实体基类BaseEntity

package com.mytest;

import org.apache.commons.lang3.builder.ToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;

public class BaseEntity {
private Long id;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
/**
 * 覆盖toString方法，目的显示所有JavaBean的属性值，省略写很多的getXxx的方法
 */
public String toString() {
return ToStringBuilder.reflectionToString(this,
ToStringStyle.MULTI_LINE_STYLE);
}
}

实体类Person

package com.mytest;


public class Person extends BaseEntity{

private String name;
private String gender;
private int age;
private double weight;

public Person(Long id, String name, String gender, int age, double weight) {
super();
this.setId(id);
this.name = name;
this.gender = gender;
this.age = age;
this.weight = weight;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

public String getGender() {
return gender;
}

public void setGender(String gender) {
this.gender = gender;
}

public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public double getWeight() {
return weight;
}

public void setWeight(double weight) {
this.weight = weight;
}
}

Example

package com.mytest;

import java.util.List;
import java.util.Map;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Function;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Ordering;

public class Example {
    
public static Logger logger = LoggerFactory.getLogger(Example.class);       

public static void main(String[] args) {
        List<Person> list = Lists.newArrayList();
        list.add(new Person(4L,"jason", "male", 16, 120.50));
        list.add(new Person(1L,"tom", "male", 48, 163.50));
        list.add(new Person(3L,"john", "male", 33, 105));
        list.add(new Person(2L,"rose", "female", 26, 90));
        
        
        logger.debug(list.toString());
        //获取ids
        List<Long> ids  = entityIds(list);  //entityIds方法
        logger.debug("---------------ids-------------------");
        logger.debug(ids.toString());
        
        logger.debug("---------------maps-------------------");
        //获取map
        Map<Long, Person> maps = entityMaps(list); //entityMaps方法
        Set<Long> keys = maps.keySet();
        for (Long id : keys) {
logger.debug("key: " + id + " value: " + maps.get(id));
}
}

/**
 * 获取表记录集合的Id集合
 * @param list
 * @return
 */
public static<T extends BaseEntity> List<Long> entityIds(List<T> list){
List<Long> ids = Lists.transform(list, new Function<T, Long>(){
            public Long apply(T entity){
        return entity.getId();
            }
                }); 
return ids;
}

/**
 * 根据实体记录，输出Map<Long id,K extend BaseEntity>集合
 * @param list
 * @return
 */
public static<V extends BaseEntity> Map<Long,V> entityMaps(List<V> list){
        Map<Long,V> maps = Maps.uniqueIndex(list.iterator(),  new Function<V, Long>() {
    @Override
    public Long apply(V entity) {
        return entity.getId();
    }
});
return maps;
}

}

 

entityIds方法

        /**
 * 获取表记录集合的Id集合
 * @param list
 * @return
 */
public static<T extends BaseEntity> List<Long> entityIds(List<T> list){
List<Long> ids = Lists.transform(list, new Function<T, Long>(){
            public Long apply(T entity){
        return entity.getId();
            }
                }); 
return ids;
}

 

entityMaps方法

        /**
 * 根据实体记录，输出Map<Long id,K extend BaseEntity>集合
 * @param list
 * @return
 */
public static<V extends BaseEntity> Map<Long,V> entityMaps(List<V> list){
        Map<Long,V> maps = Maps.uniqueIndex(list.iterator(),  new Function<V, Long>() {
    @Override
    public Long apply(V entity) {
        return entity.getId();
    }
});
return maps;
}

 

引入包，可参考pom.xml

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.gzdfbz</groupId>
<artifactId>mytest</artifactId>
<version>0.0.1-SNAPSHOT</version>

<dependencies>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>18.0</version>
</dependency>

<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.3.2</version>
</dependency>

<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.7</version>
</dependency>

<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.7</version>
</dependency>

<dependency>
<groupId>joda-time</groupId>
<artifactId>joda-time</artifactId>
<version>2.3</version>
</dependency>



</dependencies>
</project>

log4j参考：

#
log4j.rootLogger=DEBUG,console
log4j.additivity.org.apache=true

#
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.ImmediateFlush=true
log4j.appender.console.Target=System.err
log4j.appender.console.layout=org.apache.log4j.PatternLayout
#log4j.appender.console.layout.ConversionPattern=[%-5p] %d(%r) --> [%t] %l: %m %x %n
log4j.appender.console.layout.ConversionPattern=%l: %m %x %n


log4j.appender.com.mytest =  debug

 来自：http://my.oschina.net/u/221951/blog/333286

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